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Ok,

Here is an interesting fact:

Takashi Amano, the grandmaster himself, states in his second Nature Aquarium World book (page 142)

When the depth of water reaches 45cm ( 18” ) between the surface and bottom of the tank, there is more than 4 times less light intensity. This makes the cultivation of aquatic plants difficult.

So much about his take on the importance of height as a measure on light requirements.

Can Amano be wrong?

Ingo

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Proud Member of the New Jersey Aquatic Gardeners Club

I don't really think that the issue is simple. If you figure it's a matter of Lumins. Honestly it isnt that simple either, if you figure that the light is brightest under the bulb and seeing as the light will dissipate at the edges of the tank you would have to mesure the actual lumins per square inch, then build a three dimentional graph and then calculate how many lumens is lost per inch of the tank down to the substraight. Now this would still only be a theoretical number because there are a large ammount of veriables when comming up with these factors, water that is 100% H2O has a different refraction index, this can be seen when shooting a laser thru water and mesuring the angle deflection and the actual ammount of light loss to deflection from the water. Now we have a lot of other chemicals in the water, these waters are going to change the angle of deflection and the ammount of light that is being refracted. So actually mesuring the ammount of light getting to the plant would also involve figuring the depth at which the plant is getting what ammount of light.

So making a long story short, it is increadibly hard to mesure out the proper what I will call "hydroponically accurate" ammount of light in water due to the many many variables, not like when dealing with air.

So yes it could very easily get contorted into something extreamly complicated but dealing with ideals you only need to really know two things Lumins per square inch at the surface of the water and then the theoretical absorbtion of light by water per inch of water (or metric counterparts respectivly)So WPG is actually completly over simplified but basically it takes in account "standard" tank sizes and depths and doesnt account for oddly misshapen tanks. If anyone likes I can do up some research and throw togehter an equasion but i think that the 1wpg is an ok standard for "Standard" tanks is fine but past that you will need to factor in height

Bensaf,

The majority of your post is summarized by minimum light threshold and/or that plants need a minumum amount of light to thrive. Again, there is nothing wrong with quantifying what we observer. If this was not true, PMDD would still be the standard, for example.

Joe

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http://justanothertank.com

Oh for God's sake sake guys give it a break. You are bringing over-complication to whole new level. Put away the slide rules and the equations, it's way simpler then that.

Why does the WPG thing go screwy when we deal with very small tanks and very big tanks . Simple it's the bulb size. A 10 watt bulb over a 10g is 1WPG , a 100 watt bulb over a 100g tank is also 1 WPG. Is it the same ? No. A 100watt bulb is simply more intense light then a squiddly little 10 watt bulb. End of story.

Assuming you want to overcomplicate it further. Lets take a high light plant like Macrandra, assume the tank depths are the same, put it in a 10 gal under a 10 watt bulb and put another in a 100g tank under a 100watt bulb. Where do you think it's going to do best ?

Does this mean a 100watt bulb is 10X more intense then a 10 watt bulb ? No. Obviously the 100 watt bulb is going to be longer so the light is more spread out. But still a, for example, a 3" section of 10watt bulb is going to provide less light then a 4" section of the 100 watt bulb. Watts is simply a measure of power to drive the bulb. The more power pumped in the , the more light produced. Think of the old incandescent bulbs. A 40watt bulb was exactly the same size as a 100 watt, but a hell of a lot brighter. How much more intense ? I don"t know, and don't really care either. Maybe one of you math freaks can figure it out.

So very small tanks need more "WPG" big tanks need less to get the same effect.

As for Amano, don't know the scientific details, but a look at any place in the wild where you will find aquatic plants will tell you a lot. Almost all plants will be found along or close to the bank, you'll find little to no aquatic plants more then 18" below the surface. There's a reason for that.

Planted tanks can be as simple or as complicated as you want them to be. I prefer simple. Choose the right plant, adequate light and Co2, chuck in a few powders every day ,test nothing, change the water a bit on Sunday. KISS.



Last edited by bensaf at 17-Nov-2005 22:03

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Some days you're the pigeon and some days you're the statue.

Remember that age and treachery will always triumph over youth and ability.

I like your tanks.

I have a buddy growing Ludwigia repens in a 1.1wpg 75g, fwiw.

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http://justanothertank.com

nice setups they put mine to shame.

OK, so basically all things being equal, the depth of the water likely does make a difference.

I see what you are saying about the equipment.

If i were to put exactly the same setup on two different height tanks, with the same plants nutrients etc, there is probably going to be variation in the growth between the tall and the short tank even if the depth of the water is the only major difference. Yes?

BUT if you think about depth and lighting issues, in the scheme of things, the problems that it may cause are easily overcome with the use of more focussed and powerful lighting.

OK, cool

I am more than a little interested in this, I just bought a 48x14x20" tank, and only have 2x40w tubes for it. I was going to do a direct swap of everything that is currently in my 24x12x14" tank which has 1x20w tube.
Even though the total WPG on the 4'er is now 1.4wpg instead of the 0.8wpg on the 2'er, its a good deal further away from the substrate and the plants in general.

I have no doubt the plants will be fine, its only java fern and hornwort atm, but it will be interesting to see if the lower parts grow more sparsely than the parts that recieve more lighting

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,

Let me preface my post: my tallest tanks are 12" and I am only explaining what I understand from my favorite gurus. I do not have tall tanks to play with, but my goal is to grow whatever I want, and I try what my gurus try with their much larger tanks. My progress on my last project is logged in my homepage link on this site, flaws and all. Do not listen too much to me.

Lets use the standard of growing plants for a moment for "better." Lets assume 10" of height matters: you're right; it makes sense. It doesn't matter as much as, say, reflector's efficiency in focusing light into the tank, nutrient dosing, carbon, and other things.

Certainly more important is the reflector. Check this out:

2x23w Spiral screw-in CF, painted white hood (it is important to note that restrike -- light lost from bulb shape -- is an important factor.)
2x13w CF, AH Supply reflector (Deluxe bright kit)

The light in the sump is the same in both pics, for comparison. I think more light is hitting the bottom of the latter pic than there is four inches up in the first pic. I think the lighting in the second pic hitting the bottom of a 24" tank would be more than it would in the first pic. Note the second pic's setup has less watts than the first. The quality of the reflector is as important as anything imo.

Lets look at 1.7wpg over 10g again. Lets play with my sump instead, which has 23w spiral screw-in flourescent, 2.3wpg, in those pics. Most of my plants are floating real close to the light. I grew anacharis, hornwort, anubias and java moss fine. I could not grow wisteria, a medium-low to medium light plant by all acounts, well until adding another spiral screw in flourescent.

Set up in July. (All the plants in the first two pics are still in the main, btw.)

My best advice to other aquarists is to pick good gurus. There is a reason Tom Barr, Diana Walstad, et al talk more about nutrients than light. When considering light, efficiency (reflector, CF or better, proper bulb shape, etc) is much more important than height. I would make the argument that height does not matter very much at all.

Some people more experienced than me think the things we are talking about here make things way more complicated than they need to be. Some of them have very beautiful and effectively algae-free tanks.

Check this out

She is growing very difficult plants. Many of those plants are still thought of as rare in the hobby, one year later. Notice that she is also keeping shrimp known to be sensitive. She has said she does not care much about measuring and such. A few days ago I paid ~$50 for less than a 10g's worth of Amano's ADA AquaSoil to try to grow some of those plants better, and I am normally the DIY type (aka cheap ).

Pick good gurus

Hope this helps.

*links

Last edited by czcz at 13-Nov-2005 23:27

Last edited by czcz at 13-Nov-2005 23:31

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http://justanothertank.com

Ok, sorry, having difficulty following. Miss Average very-bad-at-maths here. I'm trying to wrap my head around this.

If i'm following, the idea thought to be most correct is that depth makes little to no difference if total depth is under 2'.
It makes little to no difference to what exactly? the light intensity at the base of the tank? Surely there is some difference between 12" and 24" tanks?

Forget changing the way we measure things for a moment (because for me that adds a whole other layer of complexity, being that by chaging the way we measure something, the something in question can change) and have a try at explaining to me in language you'd use on a high school kid.

Why, with all things being equal, wouldn't the lighting over a tank with a total depth of 14" be more intense at the final destination than with a tank with a depth of 24"?

I have no interest in the benefit to plants, or types of lighting or substrates and displacement etc, I just want to know what happens to the light as it passes through water and why we don't lose a good deal more of it over 24" than 14".




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

LITTLE_FISH,

Unless dosing and CO2 are equal in the two tanks only looking at light and height difference is a flawed experiement. If they are equal it only shows that guidelines can be broken.

While I am in awe of his tanks, skills, and talent, I do not take much of what Amano says seriously. Some aquarists are all open source, and some keep secrets and charge $25/50mL of something called ECA. It is this way in every hobby.

Matty*,

Like much of the krib, that calculation is good. It yields ~45watts of light over my 8g for example, which is what I need to grow most of the plants I want. This does not eliminate Rex's attempt to derive data from large tanks to apply it to small tanks. I think we would both agree the why is important.

Mrwizerd,

Accounting for displacement of substrate is always good, but the WPG standards are already rounded to closest integer (~2wpg being the accepted standard for medium light, for example) and seems to have been developed before people consistently substracted displacement of stuff. Many still do not account for displacement when dosing ferts, for example. You seem adept at math and I encourage you to look at the kribs or Rex's thoughts or come up with something new if you are interested in this type of thing.

While I like the math I understand it only goes so far. Still, attempting to quantify what we observe is never bad.

Hope this helps,
Joe

*=edit. sorry Megil.

Last edited by czcz at 13-Nov-2005 21:12

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http://justanothertank.com

Not that I am an expert or anything but wouldnt the WPG in a 10g be more like 2.13wpg when considering a 3ish inch of substrait takes up a sizable space when thinking of volume especially if it is fine gravel to sand? Therefore by calculating actual water volume instead of theoretical volume of water you would get a better mesure of your true wpg considering the rate at which water absorbs the light?

Granting that the equasion using lumens or angstrums would be a better guideline for someone who understands the math, but for average Jo WPG is an easier judge unless there is an odd depth custom built tank that they are dealing with and if this where the case I would assume them not to be amatures.

Just my two cents.

Ingo,

If I remember the equation for light intensity correctly, then it is than intensity is inversely proportional to the square of the distance. Thus light intensity at a distance of one foot is four times greater than light intensity at two feet and nine times greater than light intensity at three feet.

IMO few hobbyists who use CF or F lights have a distance from light source to substrate of greater than two feet. Yes, some specialty tanks will be deeper and probably set-up for tank re-arranging cichlids.

I think the wpg rule allows for the "standard" range of light distance to substrate of 16 to 22 inches on larger tanks. So glossostigma in those tanks demand bright light as it is a substrate level plant. In actuality, the plant in shallow water would require just one-fourth of the light intensity that it demands in a deeper tank once its minimum light requirements are met.

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

Gang,

Rather often we have here a question like “What lights do I need to grow (what) plants?”

Just yesterday, someone asked this question again and subsequent responders (me being one of them) concluded with opposite results. I have no scientific basis for my conclusions; I just try to use my common sense which might be totally wrong.

The basic numbers in the particular tank in question were 10G and 17W of Fluorescent Light, so that would be 1.7wpg. The conclusions were that it is a Low Light Tank (two experienced members said that) and, opposite to that, that it is a Medium Light Tank (which was my answer).

Now, what is it? And in particular why?

Here is my thought process (always assuming that Lumens etc. are the same for all situations):

The deeper a tank is the higher has to be the wattage to reach the substrate with enough strength. If we consider a medium sized tank, let’s say a 29G, with 2wpg as a medium light tank, then a tank with just 15% less light but 50% more height (assuming the 10 is 12” high and the 29 is 18” high) should be at least able to grow the same plants, if not even more.

That’s at least what silly me is coming up with .

Thanks for your input, the always curious (and confused)

Ingo

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Proud Member of the New Jersey Aquatic Gardeners Club

czcz,

I try not to get caught in my own assumptions .

I started out in this hobby only about 9 months ago and the single most surprise to me is how many tank related issues are unresolved and probably discussed over and over again. For example light requirements, maintenance routines, and plant fertilization. While I was (am) disappointed on one hand that there are no clear guidelines, I am excited on the other hand because I can feel like an explorer in uncharted territories (well, I might exaggerate a little ).

Matty,

Yup, I read this FAQ, but it does not distinguish between tank sizes (small, medium, large). I would assume that it works well for you because the tank that you use in your example is of “average” size.

Ingo

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Proud Member of the New Jersey Aquatic Gardeners Club

Yes, a very good link CZCZ it explained in scientific terms why my son's 5 gallon aga tank with a 25watt bulb is not high light.

My Scapes

Does anybody read the [link=faq]http://www.fishprofiles.net/faq/plant-lighting.asp" style="COLOR: #FFD700[/link]?

This relatively simple calculation provides spot on accuracy to my taller tank. I have a 38G tank, which is 36X12X18. With gravel it's only 15inches tall. Check this out:

36*12*15 = 6480

6480*.12(medium light plants) = 777.6

777.6/11(hours) = 70.7 Watts over the tank.

I have 80 watts over my tank. I can grow medium light plants, but cannot for the life of me grow any high light plants.

This rule is still general, but tends to be quite a bit more accurate. The WPG rule is even more general and is used for simplicity's sake for the newbies. Advanced aquatic gardeners don't need any rule, but go simply by experience.

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Critical Fertilator: The Micromanager of Macronutrients

Ingo,

Rex is not right about everything, and it is only another imperfect metric and guideline. It is good that you are thinking objectively and analytically; I did not mean to suggest you should stop doing so: more people should in this hobby.

Joe

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http://justanothertank.com

czcz,

Thank you so much for this link. Although it is a little over my comprehension level, it sounds convincing. The only argument I had still left was the depth issue as it is left out of his equation, but on another page on his site he says:

Ok, [rant mode on] I have seen a lot of people repeating the lie that deeper tanks need more light

Now that makes it clear what he thinks about my argument

So, I guess we can conclude that what he says is true. As such the only nice things to have would be a) a lux value for all our lights and b) a table that shows the sliding requirements in lux to achieve a certain light level depending on tank size (as he says, less for larger tanks, higher for smaller ones).

Excellent link, thanks a lot

Ingo

EDIT: Afterthought – but why do my plant grow better in my smaller tank than in my larger one (in this example here, not my really large one)? And I thought I had it all explained.

Last edited by LITTLE_FISH at 09-Nov-2005 14:42

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Proud Member of the New Jersey Aquatic Gardeners Club

IME it is a low light tank. Forget about tank height for a moment and consider if wpg, a measure of consumption, is really a valid metric for determining light output. Applied experience says wpg breaks down in small tanks because medium and high light plants need a minimum amount of light to thrive. Try growing glosso with a four watt CFL over a 2g, for example.

If you have a very good reflector that focusses light into the tank, tank height is not so important, especially 6".

Ratios are flawed for a reason.

Rex Grigg has some interesting but poorly explained ideas on this, including the thought that lumens per square inch (LSI) is a better metric than wpg.

If you'd like, check out my tank link in my profile. I need 26w CF + 20w NO to grow high light plants (P. stellata, Ammania sp. Bonsai, etc) in a 12" tall 8g. There is no way I have as much usable light as 5wpg over a 40g breeder. I have upgraded lights a few times based on observation of plant health, and you can see how the plants did at the bottom of the page and the images link.

Do some searching. Look at the lighting over the AGA competition nanos. Hope this helps.

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http://justanothertank.com

Bob,

While I hear what you are saying, I think you are somewhat circumventing the questions .

I would like to leave any parameter that could change the picture out of the equation. For example, we would never question a person that has 2wpg of where the wattage comes from (PC or reg. Fluorescent). But maybe we should as I completely agree that PCs are more powerful. But the same can be said about normal fluorescents when comparing T12, T10, T8, and also T5, not even to mention MH.

My point refers to one kind of light (may it be PC or regular), just with a different wattage and a different tank size.

I think that a global statement that 2wpg are acceptable as a medium light tank identifier cannot be made as tank height plays a significant role. I am not an expert in measuring light intensity at various depths, but I believe to remember that an increase in depth of 50% lowers the light intensity to a multifold of that percentage.

renoharps,

Yeah, I meant 50% less height for the 10g, where the 10G is the base value. As I said, I am a little confused .

renoharps and Bob,

I concur with renoharp’s statement that the 65W on a 29G will grow less light requiring plants than 24w on a 12G. My example is my 20G Long (same height as a 10G) with 40w (2wpg) Regular Fluorescent that has better plant growth than my 29G (50% taller) with 65W PCs (2.24wpg). Height is an important factor.

Ingo

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Proud Member of the New Jersey Aquatic Gardeners Club

Ingo,

I agree with your height assumptions on lighting. That is one thing that is forgotten - the distance of the plants from the light source. I have 24w on my 12g and I can grow high light plants in it. I cannot however grow high light plants in my 29g with 65w.

And actually, I think you meant 50% less height for the 10g, right?

Last edited by renoharps at 09-Nov-2005 11:25