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Calla,

What a great question!

I am actually not wondering about this myself as I adopted this rule. Why did I do that:

based on my neons (that have a frequent die-off) I have been able to observe the fish in numbers ranging from 9 to 1 in my 29G.

How do I define a school: that is a hard one. I think by seeing the fish behave most like what I would assume to be natural, as in swimming out in the open in confidence, huddling, and the least infighting. Once my neon group got below 6, one or more of these behaviors went away, usually the swimming in the open as a group thing.

In nature, a school often measures hundreds to thousands of fish, so no real comparison can be made in our tanks (except my Espei, of course ).

If a hobbyist has enough space (as in can have additional fish) in his tank I usually suggest more than 6, as often one or the other doesn’t make it and then an initial group of 6 would fall apart.

Will a group of 3 fish in your tank survive? Most likely, at least for a while. Will they be as happy as if they had more of their kind with them? I think not.

I am not a Cory expert, but aren’t they in nature also in large groups?

Just some thoughts,

Ingo

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Proud Member of the New Jersey Aquatic Gardeners Club

ACIDRAIN of course lowered the pH of the water by falling on it!!!

Sorry, couldn't help it .

Regarding the mathematical discussion at hand, I believe you have misunderstood each other. (Just to clarify: I'm no mathematician and will not get into the general discussion.)
I believe Acid means that in order to have a satisfying odds (who ever decided what a that satisfying odds would be is another q.) of getting a pair you need six individuals and to have the same odds of getting TWO pairs you'll need twelve individuals. Right? Wrong? Cause if you mean what Bignose thinks: that you'll need the extra six to have an added chance of getting the FIRST pair then a signed statement from Einstein himself wouldn't convince me.

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So here I am once more...

". And yet, now you state that there would be an, and I quote, "obvious skew". Very confusing on your part. And your statements use the words/phrases, "obvious" and "certainly not", and yet you don't have any scientific backup. These words have a 100% meaning to me, and if it is so, please show me the data, as I cannot find any to back up your statements."

Let me clarify. What you’re saying is that numerous studies have concluded that six fish is the ideal number by which one can obtain a fair sex ratio, with one taking into consideration “variations”, as it was so put. But how can you generalize that this six fish figure is applicable to all species of fish? You can’t. Mathematically, you increase such chances with each purchase. And, if you can, I’d like to see “actual articles, links, data...please show me the data, as I cannot find any to back up your statements” (since you are so intent on playing the quoting game). I would like to see how they came to this conclusion of six fish being particularly effective one way or another, mathematically and biologically, and set the said result so that it would pertain to ALL species of fish. While I am aware that the “six fish” rule is often used to obtain a sizeable harem of two-sexed fish, I have generally dismissed it as an old wives tale, and will continue to do so unless you’d like to give me an official scientific study done otherwise. Of course, should there be such a published report in existence, I will most definitely desist.


”And, there have been studies of this nature performed on more than just the kirbs. There are many DOCUMENTED sources out there on other fish, from other continents, living in other water parameters, etc etc. Multiple sources state there is a differenciating ratio of males to females with multiple different parameter changes, with multiple different species of fish.”

Depends on the morphology of the fish. A harem breeder will most likely have fewer males represented in the population than females, no? I did NOT say that there was no such variability and I have no idea where you pulled that one from.

"At first I started out using tap water for about half of my study, then changed to using 100% RO and manipulating it manually. One colleague used strickly tap water, and the other used strickly 100% RO water. (side note; the one of the colleagues that used the RO, is a chemist, and one of the BOT of the ACA) Our measurements of the hardness were tested with electronic testing equiptment, as well as tablets. We kept the dissolved solids a constant.”

How did you manage to balance out the hardness salts EXACTLY to the specifications of the tap water you replaced with RO? I find it difficult to believe that you yourself replaced the salts with no ill effect on the fish. Most compounds containing such chemicals release their own F.R.s of chlorides and metals (definitely not beneficial for fish, and with the amount you're adding, I doubt that you'd be able to tailor dechlors, which do not even remove the metals to recalculate in an exact manner to rid the water of exactly that amount of chlorine present), and water treatment chemicals are not generally available to the casual chemist. However, I’m obviously wrong if you’ve done so; after all, I don’t have much understanding of softening the water then purposely re-adding hardness salts and trace minerals. I'd assume that the mere analysis of the water to percipitate out the exact quantity of each specieif chemical that was originally present in the tap would already cost quite a damn bit of money. RO has no DSs, as I recall. Furthermore, what manner of acid did you use? It’s awfully difficult to monitor such an additive without measuring the effects on fish(just speculation; I’ve never heard of such an action so I can’t speak for myself). Also, I would kindly request you to not play the documentation game with me, as if you recall, I noted that I was speaking out of my first and second-hand experience on the matter. Or if you would rather, I can play along; have you any charts or measurement results yourself? Surely you must have something after having partaken in such a lengthy experiment over such a period of time. Also, I would prefer that you not insinuate that I’m falsifying the background I’ve given, as I am not, and I don't appreicate being called a liar. The breeder I have contacted in regards to the situation at hand is Dr. Michael Lim, well known here primarily for discus.



Last edited by Cup_of_Lifenoodles at 18-Jan-2006 21:18

"The math does show it, but the thing is, when you go to purchase some fry, in hopes of getting at least one of each sex, which equation are you going to use to determine how many you purchase, in attempt to get a pair? If you have no idea the ratio?"

This is rhetorical, right? The math shows you purchase as many as you can because every additional one you purchase decreases the chance of getting all one sex. NO MATTER WHAT the distribution is. This has been the point of my last few posts.

There are certainly other factors that go into it, cost, temperaments, requirements, all the things you mentioned and many others. But from a pure mathematical point of view, 6 is not a "magic number". You increase your chances of a pair with every additional one you purchase. If your only requirement is the best chance to get a pair, you always get as many as you can!

I go with six for a simple reason. At my fish store, they will specify schooling fish you can buy for cheaper if you get a group of three. Therefore, it's convenient to get six since it's a better school and usually hasn't yet crossed the $10 margin when only getting six.

Though if I started a fish store I'd definitely give thought into cutting the price for buying six in a group. Of course, for reasons of profit, business, and economy there's probably a good reason why most fish stores don't.

In any case, the more the merrier.

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The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian.

Common sense, my man, common sense. On obvious increase in total dissolved solids will most definintely affect embryological growth in pelvachromis, but in rift lake species, were the same morphological standards to be set, there would be an obvious skew in the concentration of males to females and vice versa. Thus, well, you get the picture.

No I don't get the picture, mind explaining it to me? Your statement is confusing and basically stating that if the same morphological standards were set, then the Rift Lake cichlids would produce the same effect as for male to female concentration. "There would be an abvious skew in the concentration of males to females and vice versa". Thus, if we changed the parameters in some way, they would sport a ratio like the Pelvicachromis. And yet in your prior post you state,

certainly not applicable to their chromid relatives in the rift lakes.

. And yet, now you state that there would be an, and I quote, "obvious skew". Very confusing on your part. And your statements use the words/phrases, "obvious" and "certainly not", and yet you don't have any scientific backup. These words have a 100% meaning to me, and if it is so, please show me the data, as I cannot find any to back up your statements.


And, there have been studies of this nature performed on more than just the kirbs. There are many DOCUMENTED sources out there on other fish, from other continents, living in other water parameters, etc etc. Multiple sources state there is a differenciating ratio of males to females with multiple different parameter changes, with multiple different species of fish.

Then how can you possibly assume that the “rule of six” is applicable to any other species save the one that you personally spawned?

I did not "assume", as I stated, there are multiple documented instances of this happening with other species, genra, from other lands, other water parameters, etc etc. And the rule of six, I am not assuming either, but I am taking the advice of those accredited persons that did a much larger study than mine, on other fish. As well as the advice and recommendations of the multiple, multiple, multiple accredited orginizations out there on the subject of the aquaria, hobby, breeding, and fish keeping in general. My assumption is they are correct in their findings and recommendations, where as you are not. As many of them are either scientific organizations, or have a scientific branch, I feel their info very much accredited. If they state the "rule of six" to be the best bet, and you state,

In any case, the rule of six is complete bologna.

Guess which statement I am going to believe, and follow. And to use a quote from your own post;

Thus, well, you get the picture.

Oh? How did you lower the pH, then, might I ask? Pour acid straight into the water? Almost all pH lowering mechanisms in the home aquaria conincide with a drop with dissolved solids.

At first I started out using tap water for about half of my study, then changed to using 100% RO and manipulating it manually. One colleague used strickly tap water, and the other used strickly 100% RO water. (side note; the one of the colleagues that used the RO, is a chemist, and one of the BOT of the ACA) Our measurements of the hardness were tested with electronic testing equiptment, as well as tablets. We kept the dissolved solids a constant. As for lowering the ph, well yes, we used an acid. Only thing I have ever used to lower ph was acid. Actually did not even realise there was other stuff to lower it till about 5 years ago, lol.

And Cup, if you want to argue/discuss a point that is fine. But as I have stated in posts/threads in the past, please bring actual articles, links, data, with you to the forum. To back up your evidence. As, he said, and she said, and a prominent cichlid breeder said, etc etc, just don't make it so. I don't know who he or she, or even the prominent cichlid breeder once residing in the area is. So how can I take this info you give as to be confirming? How am I to know the truth behind it? The factual documentation does not always make it so either. But, it is definitely grounds to stand on. And will help make the case at hand a stronger arguement.

_____________________________________________________________

There is always a bigger fish...

"Wrong, it was and is the ph. I did the studies with over 50 spawns, along with 2 of my colleagues. The only manipulation done was the ph. All other factors were the same for each spawn of that part of the study."

Oh? How did you lower the pH, then, might I ask? Pour acid straight into the water? Almost all pH lowering mechanisms in the home aquaria conincide with a drop with dissolved solids. I have partaken in a similar “study”; more accidental than anything (I outlined this in another post). Over the course of two years I had two breeding pairs (alongside two DD pterophyllum). To trigger spawning the first few sessions, I used fifty percent RO changes, lowering the TDS counter to almost 100, while subsequent spawns yielded fry without much hardness tweaking. Southern Californian water is well buffered, but hardly basic, so in reality, the pH fluctuated only half a reading. When the first two spawns grew out I noticed that, as opposed to follow up spawns, the sex rations were tipped in the favor of female production. In a follow up discussion to a post on these boards, I contacted a prominent cichlid breeder once residing in the area, and he confirmed my suspicions, having worked with other pelvachromis as well, concocting multiple spawns.


”The krib is the fish I personnally did the study on.”
Then how can you possibly assume that the “rule of six” is applicable to any other species save the one that you personally spawned?

“ I would like to read it, or at least hear about how it was done, and what changes/differences were studied that make these "certainly not applicable to their chromid relatives in the rift lakes".I would be very interested in the results, so I can add them to my speaker program on breeding.”

Common sense, my man, common sense. On obvious increase in total dissolved solids will most definintely affect embryological growth in pelvachromis, but in rift lake species, were the same morphological standards to be set, there would be an obvious skew in the concentration of males to females and vice versa. Thus, well, you get the picture.

First off, staying on topic with this thread;

Cali, I feel the number 6 was just an overflow to the subject of a school, because of the need and/or want for at least a pair. Even if not breeding, many fish will show better activity and/or better coloring if there is at least one of each sex. A lot of the high activity you see in schools of fish, is actually breeding activity. Take for example and school of 6 tetras, 2m/4f. They will be much more active in the water, swimming and breeding all the time, than say 5m/1f. And way more active than just 6 males or 6 females. The males are probably bolder than the females, but will be less active if no females are around to breed with, or even to impress to try to breed. Many of these schooling fish are harem breeders. Meaning the females will spawn with multiple males and such. This enlarges the gene pool of the few that survive. No the fish don't understand about that, but nature does. And with harem spawning, the females are more active with multiple males within the group.

I don't feel it is always the correct number, as more is always better, for activity of the fish, comfort of safety in numbers, and just general nice appearance to our eye. And, like all animals, they are each individuals with their own personality and such. Many fish that need to be in schools, may act the same way when they are a singular fish, or with just a couple/few. I think it is more of an individual fish that decides. But this is the reason I feel the number 6 is the number of choice.

Another thought, is the size tank needed for said fish. In other words, the smallest size tank needed for most schooling fish, and the highest amount recomended for said tank. This is thought is an average of all the "schooling" fish. Lets say a tank size needed for one tiger barb. I would say at least a 10-15 gal tank, as it needs running room. So lets go with the 15 gal. Now how many more can you put in there with the one, and maintain a logical bioload, as well as maintain the needed running room without them running all over each other? OK, 6 is a good number. Too many more than that and they would not have the room to run, as they would be everywhere. And, you would not have any bioload expansion left for any other fish. Maybe the number 6 is used as an average, to tank size and fish requirements, and still some space left for other fish. Maybe the number 6 is generally used in a combination with everything discussed thus far. IMO that is the best answer, a combination of all.



Now, as for the study;

and while kribs may be more e to turn into one sex as opposed to another due to certain DSs (not pH),

Wrong, it was and is the ph. I did the studies with over 50 spawns, along with 2 of my colleagues. The only manipulation done was the ph. All other factors were the same for each spawn of that part of the study. The ratio in each spawn of the varied ph values was less than 2% varied with each measurement of ph value.

such is certainly not applicable to their chromid relatives in the rift lakes.

The krib is the fish I personnally did the study on. For reasons like there was some question as to why most of the fry of these fish being bred and raised in local tap water, were coming out highly males. As well as other reasons of cost, proliferation, parenting, size, ease, and other reasons. It is by far from being the norm of all fish. As for the rift lake fish, I have no idea, as I did not use them in the study, nor have I heard of anyone doing any studies on them in this nature. As for your statement, when was the study done to determine that it is not? I would like to read it, or at least hear about how it was done, and what changes/differences were studied that make these "certainly not applicable to their chromid relatives in the rift lakes". I would be very interested in the results, so I can add them to my speaker program on breeding.

As for the mathematics;
The math does show it, but the thing is, when you go to purchase some fry, in hopes of getting at least one of each sex, which equation are you going to use to determine how many you purchase, in attempt to get a pair? If you have no idea the ratio? If you have not the knowledge to know what the water parameters were, or the knowledge to know what the ratio is in said water parameters. You could say you would buy them all. But, what if it is 300 fry, and they are a rarely bred species that get 12+ inches long and will not show sexual differences till they reach at least a size of 8-10 inches. They are canibalistic, and intolerable of each other unless paired, and they are going for $45 each? So even buying all of them, you will need many large tanks to hold 300 ten inch fish. This scenario, is of a fish that I spawned. It was only the third documented spawning of this fish, and no real info was available about any ratios of sexes and such. The water parameters were different from their natural habitat.

_____________________________________________________________

There is always a bigger fish...

The great unknown to me here is where the number 6 came from, as a general guideline.

Is it a child of this Site, or does it occurs on other sites as well? If we follow ACIDRAIN’s tale from a long time ago , then I would have to assume it is widely used. Now, not naturally being a person that likes to follow the flock just because, my own very limited experience has supported the number 6 and I am more than willing to follow in this instance.

To me this is like one of these rules that the farmers use. They have no scientific proof on any of their rules (although I am sure some of them have been analyzed by now), but usually they tend to be right. If 6 is broadly used for years already and (in general) nobody has come up with a better scheme yet, then this is an acceptable number to recommend.

And, although I am only experienced with this number when it comes to neons, I am willing to broaden it to most other tetras. When it comes to cories I am weaker, but I have many times seen small groups (around 3) in tanks at the LFS and they sure didn’t seem happy. On the other hand, larger groups (from what I remember they were more than 6 though) were much more active.

Just some more thoughts,

Ingo

Last edited by LITTLE_FISH at 17-Jan-2006 08:23

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Proud Member of the New Jersey Aquatic Gardeners Club

I've noticed a huge difference in under 5 schooling fish and over 6 fish. My black neons, congos, threadfins, pandas, julii, and those unknown cories from walmart all act extremely different when I bring the numbers over 5. They hide less even when there is nothing around to scare them, it takes alot more to scare them, they are more agressive when feeding, and have more color. Yea 5 can work and 3 may live fine but for the best chance of having natural behaviors and limiting stress more is better. 24 would be great if the standard tank kept was 8' long but it's not practical. Generally if the tank is actually big enough for that species to be kept then 6 of them will fit. If we don't draw the line at 6 as the best number then where? 3? Someone can always say 5 is 1 less than 6 and 4 is one less than 5 and eventually we have a tank with 10 pairs of different species instead of 2 schools and the fish show more stress than if they were in just 2 schools.

Sometimes 5 is fine but if someone is planning stocking from scratch I'm always going to suggest at least 6 if not 8 of most schooling/shoaling species because I've seen that in those numbers most of the fish experience much less stress than lower numbers. I don't see 4 or less fish as a school but as a scattering of a few individuals because that's how they act in the tank. They show practically no schooling behavior when you have so few and when any of my schools got that low I barely saw that species because they'd hide out all the time, scatter when I just walked near the tank, and be very submissive when feeding.


I guess first we'd have to agree on if schooling fish really do benefit from increased numbers or if they can be kept in just a pair before we agreed on where to draw the minimum line.

very interesting thread - it's sort of joined to why i was enquiring in another thread about how big people's largest schools are and whether they observe a difference in behaviour in the large groups. i think we can safely assume that certain species feel safer and less at risk from predation when they are in large numbers, but i totally agree that 6 is purely random. having kept lots of tetras for almost 30 years, and starting out small and working up to big tanks, i can say with absolute surity that more fish (of schooling species, obviously) equals better breeding and more vital, energised fish. 6?? pah - go for 16!!

well, it varies from species i would say...i just added another lemon tetra to my school of five. since the addition last night to make the group number six, they now venture to the top of the tank and instead of hiding in the most densly planted covered side of the tank, they swim in the middle and rowdily chase themselves around in a never ending game of tag, they are also starting to display more behavior, and the one i added colored from silver to almost the same bright yellow of the ones i have had and been conditioning for months in 24 hours,lol.

school size does make a differance. my experience is it varies species to species. my corys didnt get inquisitive and "fun" to watch till there was 7 of them...and one is a bronze that doesnt look like the julii/leapords. i would say for corys to be happy to an extent and generaly content/not shy, 3 seems to be the minimum in my experience. i slowly added corys based on what people here told me, and with the last edition of a leapord cory, the 7 of them were all happy, and now sleep together instead of by themselves or in duos.

with the tiger barbs i had, 6 doesnt do jack,lol...try nine and they still arent happy and still are agressive.

im not an expert, but just my experience, six does seem to be a magical number, does it mean it has to be strictly followed? no. does it mean that it 6 will always work? not hardly.

but hey, whatever works. the best i have found is to ask people here who have kept the fish i am interested in about their behaviors with or without schools and how big the schools.

If we're taking into account "variants", then how can you possibly use six as the baseline to regulate gender dispersion amongst all osteicythids (spelling)? Each species is noticably different in its respective embryological development, and while kribs may be more e to turn into one sex as opposed to another due to certain DSs (not pH), such is certainly not applicable to their chromid relatives in the rift lakes.

In any case, the rule of six is complete bologna.


Last edited by Cup_of_Lifenoodles at 17-Jan-2006 00:28

i hate math :%)

*Chelle*
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I love the fishes cuz they're SOOO delicious...

Acidrain, that is true that the fry aren't all going to be 50/50, but the statement that 6 is the 'best' number for picking fry and then that only getting up to 12 is silly. The mathematics don't bear that out. The math will shift a little, but the changes will be incremental with number, 7 will always, always give you better odds of getting a pair than 6... no matter what the distribution is unless you know it is 100% F or M.

I can calculate the distributions given any splits you want:

It is just a binomial distribution. Let p = probability of a fry being male. Now let M = number of males and let F be number of females.

% of having M males and F females = (p^M)*((1-p)^F)

Pretty simple equation taking into account all the variances you want. You will have to know how temp, pH, etc. affects p, the chance of fry being male, but given that you know that chance, the distributions are easy to calculate:

Let's use 6 fish (since that seems to be your golden number)

If the M/F is 50/50 there is 1.56% of all M and 1.56% of all F
If the M/F is 60/40 there is 4.66% of all M and 0.41% of all F
If the M/F is 70/30 there is 11.7% of all M and 0.07% of all F
If the M/F is 80/20 there is 26.2% of all M and 0.006% of all F
If the M/F is 90/10 there is 53.1% of all M and 0.0001% of all F

7 fish

If the M/F is 50/50 there is 0.78% of all M and 0.78% of all F
If the M/F is 60/40 there is 2.8% of all M and 0.16% of all F
If the M/F is 70/30 there is 8.2% of all M and 0.02% of all F
If the M/F is 80/20 there is 21.0% of all M and 0.001% of all F
If the M/F is 90/10 there is 47.8% of all M and 0.00001% of all F

Then, just because you said there is not a big break until 12

11 fish

If the M/F is 50/50 there is 0.048% of all M and 0.048% of all F
If the M/F is 60/40 there is 0.36% of all M and 0.0042% of all F
If the M/F is 70/30 there is 1.97% of all M and 0.0002% of all F
If the M/F is 80/20 there is 8.6% of all M and 0.000002% of all F
If the M/F is 90/10 there is 31.4% of all M and 0.000000001% of all F

12 fish

If the M/F is 50/50 there is 0.024% of all M and 0.024% of all F
If the M/F is 60/40 there is 0.22% of all M and 0.0016% of all F
If the M/F is 70/30 there is 1.38% of all M and 0.00005% of all F
If the M/F is 80/20 there is 6.87% of all M and 0.0000004% of all F
If the M/F is 90/10 there is 24.2% of all M and 0.0000000001% of all F

Not really a whole lot of difference between 11 and 12, really. For that matter, not much of a difference between 6 and 7. I think that 6 is a just a good compromise number, unless you know what the distribution of fry is, then another number may be better.

Mainly, making statements like "Now, the only way to better your odds in this scenario is to jump up to the 12 number" is not right. It is a horrible misapplication or misunderstanding of statistics. For example, lets say I am a baseball player with a .200 batting average. In other words one out of 5 chance of getting a hit. I go four at bats without a hit... I am in no way guaranteed to get a hit next time. TV announcers would be saying "I'm due". But, if the true chance is .200, then the next time I step up to bat it will still be .200.

Same thing... flip a coin. Its heads. Is tails next? Of course not. Or the roulette table. Comes up red. Is black next? no. Both these cases are 50:50. Every time. Independent of what the previous flip or roulette spin was.

==========

I have one more example that is exactly like your fry scenario. Roll a fair six sided die. Lets say that if you roll a 1 the fry is M, if you roll a 2,3,4,5, or 6 it is F. The chance of getting any individual number is 1/6 or about 16.7% If you roll the die six times, that is select 6 unsexed fry, on average, you will get one 1. Or, in terms of fry, on average, you will get one M. But, there are certainly times when you will roll the die 6 times and not get a single 1. There are times you can roll the die 6 times and get all 1's. That is why the conditional statement, on average, must be added. If you watch baseball you know it is perfectly normal for a .200 hitter to get 4 hits in 4 tries in a single game, though on average, or in other words, in the long run he is a .200 hitter.

Now, what you are saying by "Now, the only way to better your odds in this scenario is to jump up to the 12 number" is that the only way to increase the chances of rolling a 1 is to go from 6 rolls to 12 rolls. That is just not right. You definitely increase your chances of rolling at least one 1 by rolling 7 times. You further increase the chances of rolling at least one 1 by rolling 8 times, and so on. This is what I am saying.

==========

It is the exact same thing with the unsexed fry. Let's let your fry are 85% male, but you cannot tell which is which. Irregardless of what the first 5 fry are, the 6th one has an 85% chance of being male. This does not in any way mean that if you pick any 6 fry at random you will get 5 M and 1 F. Those what all the %'s I calculated above says. In exactly the same way flipping a coin and getting head does not guarantee the next one to be tails. By your logic, if you got 2 heads in a row, you would have to wait until the 4th flip until you improved the odds of getting a tails. Which is not right... it is always 50:50 for a fair coin. The pH affects of the fry are really like flipping an unfair coin.

The odds improve from 6 to 7. You don't have to wait until 12. The odds will always improve every time you increase the number of unsexed fry.


p.s. sorry for the super-long post, but I wanted to make my point as clear as possible

Last edited by bignose at 17-Jan-2006 03:15 Kept adding examples to try to make my point clearer


Last edited by bignose at 17-Jan-2006 03:25

Bignose, the thing is, your mathmatics don't take into account all the variences.

For instance, with say 50 fry. If they usually average 50/50 m/f, then you have a more even chance of getting a pair.

However, if you take a varient like ph, and it causes the fry to be say 85% males, then only about 1 in 6 is a female. Now, the only way to better your odds in this scenerio is to jump up to the 12 number. This is why the number 6 is so special, because there is very hard to get a greater than 85% sex ratio.

I have conducted this experiment with Kribs. 7.0 ph will yeild a nearly 50/50 ratio. While more acidic, the higher percentage of females, and while more basic, the higher percentage of males. And the highest percentage I ever got was 85%. I spent about 2 years breeding several different pairs, as well as 3 different species. They all did the same. The highest ph was 8.5, and the lowest was 5.5ph. I also did a pair of albino kribs in the mix as well.

These variences are what created a need for the study, vs just a mathematical equation. Though the mathematical equation can show the percentages in these variences, it cannot show the variences and their results themselves.

_____________________________________________________________

There is always a bigger fish...

I am seeing a whole bunch of posts saying that if you plan on having cories, they must be in a group of 6 or more. Its starting to spread to other schooling fish too.

This is all well and good, but WHY 6? It seems somewhat arbitrary.

Why not 5? I'm seeing people get told that 5 cories isn't enough and that they should really get one more to make it a school of 6. Huh?

Is it that vital that one fish will make all the difference?

Please don't get me wrong, i'm not advocating single specimen keeping, or even paired keeping, and I do see benefit in large schools as they bring about a more natural behaviour HOWEVER I also see that inflexibility is something that has the potential to cause people to decide that since we are holding ground over 6 being 'the' number, and no ifs or buts, and since they might well know someone with a happy group of 4 or 5, that perhaps other things that we are firm about, like ammonia and pH swings etc might also be flexible.

Some things its worth being inflexible over, other things, not so much. IMO anyhoo.

All I want to know is why 6?
Why can't you keep a trio?
Yes, ok, there is a behaviour difference, but I'd hazard there is a behaviour difference between 6 and 24 too, and so why isn't the minimum school 24?


This has been bugging me for some time now, so i'd appreciate any thoughts on the matter

Last edited by Callatya at 16-Jan-2006 10:23

For animals, the entire universe has been neatly divided into things to (a) mate with, (b) eat, (c) run away from, and (d) rocks. - Terry Pratchett

Callatya,

It is strictly an arbitrary number, a bit like angels dancing on the head of a pin. Schools in the wild often number in the hundreds of fish, something few of us can duplicate in the aquarium. Instead, we create an artificial "set" of values for the definitiion of "school".

In the case of social fish, breeders note that discus aggression is decreased with 5 or more fish. They also indicate that maintaining an odd number in this small "school" also diffuses the aggression among the group.

__________
"To steal ideas from one person is plagiarism; to steal from many is research."
researched from Steven Wright

It is an abstract number, but it was chosen for a logical reason.
In a small species tank (say an 8 gallon). It would be ok to have 4 or 5 neons. However, with most people, the neons are likely to be placed in a community tank. Therefore, the number should be a little higher. I assume 6 is a prefered number because it's even (less change of one fish getting singled out) and because it's not too big like 8 or 10 and not too small like 2 or 4. 6 is kinda there in the middle, so it seems like a nice choice.

IMO the 6 fish rule is best used for newcomers to the hobby, just like the 1 inch per gallon rule. Many of us have 2 inches of fish per gallon at least with high quality filters, plants, and frequent water changes. However, for a newby, it's best to give them a solid rule where they can't go wrong. It is to prevent people who just started fishkeeping from buying a 20 gallon and stocking it with 10 different types of tetras but only have 2 of each. But like almost all aspects of fishkeeping, it's a guideline, not a rule, and people tend to get very anal about it.

Yes, the even/odd number thing was bugging me too, as I was always told that odd numbers work out better.

I don't know that placing human emotions on fish is a good idea, who is to say what makes a fish happy when you get right down to it? What we percieve as happy could really be any number of things. I should imagine that larger numbers would make the fish act in a way that suggests they feel more secure, but then is this behaviour natural for a schooling fish? Shouldn't they be quite alert and ready to skit off at the first sign of a predator?

For animals, the entire universe has been neatly divided into things to (a) mate with, (b) eat, (c) run away from, and (d) rocks. - Terry Pratchett