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Tap water parameters:
Ph = 7.0-7.2
KH = low (2 degrees I believe)
GH = high

The parameters in my fish only tank with driftwood seem to be the same except the Ph is not 6.0. I check another tank that didn't have any driftwood and it was the same. the ammonia and nitrites are 0 and Nitrates never go above 20ppm. What could be causing Ph to drop?

I did a test with a cup of water and put some of the food I have been feeding them into it. I waited a couple hours and tested it and the Ph dropped to below 6.5. Going to repeat teat and do a test with a cup with nothing added. Has anyone had problems with fish food changing their Ph? What ingredient should I look out for in fish foods that could cause the Ph to drop?

I can't tell you anything about the fish food lowering pH -- although your little experiment was interesting and I'm anxious to see what your repeat shows -- but with a KH so low, it doesn't surprise me that your pH is dropping.

Low pH comes from an abundance of hydrogen cations (H+). These can come from a number of sources. First, CO2 from fish respiration combines with water (H20) to form carbonic acid (H2CO3). Even though carbonic acid is a weak acid (in this case the term weak acid refers to what degree it ionizes instead of its actual acidity) and only releases a small amount of H+, it is still enough to drive the pH down. Secondly, as the bacteria in your tank metabolize and oxidize ammonia (NH3 --> NO2- --> NO3-), you'll notice that all of the H's from the ammonia are gone. They have, in fact, been converted to H+'s.

Now, in a normal tank setting, these H+ influxes are handled by the buffer molecules in the tank (normally HCO3-) which can donate or absorb H+'s to maintain a steady pH. The problem is, with your alkalinity so low, you don't have enough buffer molecules to achieve this, and you wind up with an excess of H+ and an accordingly low pH. This is going to continue to be a problem until you bring up your KH.

I recommend bringing up the pH by using 1/2 teaspoon of baking soda per 20 gallons. That should raise the KH about 1-2 dKH. Never raise the KH more than about 2 degrees per day. The baking soda will also raise your pH, so adding too much baking soda at once would really stress your fish. I'd shoot for a KH around 8 dKH (~150 ppm). That is a pretty good middle-of-the-road value, and should be fine for your fish unless you're keeping something like discus (needs lower) or mbuna (needs higher). Keeping it around 8 will also help you maintain your pH at whatever level you want to keep it at. Check your KH every day until you get it to the level you want with the baking soda.


Edit:
Reading back over your post, I just realized that you gave us the parameters of your tap water and not your tank water like I thought. I guess this is why I didn't do so hot on the "Reading Comprehension" portion of the SATs.

Can you give us the KH and GH of your tank water as well? I'm just assuming they are the same as your tap water. If they're not, all the stuff I just wrote might not help you.

A couple more questions:

How big is the tank?

What fish are in the tank?

How long has the tank been set up?

Further edit: I just caught your reply in the pH thread a few threads down, and it's obvious that you know a good bit about tank chemistry, so you probably already know most of what I described. Sorry if most of it is redundant.

All fish foods will cause the ph to drop with a kh like that. When the kh is that low there is no buffer and the acid that are just normally produced by the breakdown of fish waste and excess food will lower the ph. Most anything will lower the ph with a dkh of 2. You need to get it up at least past 3 but probably closer to 5 if you want to maintain a ph of 7.0 or slightly higher. Baking soda is the usual method for that. You add it to the new water before doing a water change and test to make sure it has the kh and ph you want before adding it to the tank. Don't add anything directly to the tank or you'll have too large of ph changes and stress the fish. Instead always mix up water to the parameters you want and then do water changes(starting with small ones) until the tank matches.

I have been keeping fish for a while now with these same tap water parameters. The difference is that I used to keep plants with the exception of a SA chiclid tank where I think I had a gravel that would slightly raise the Ph. I do not have these tank setups anymore and I do not use the same food.

Difference between then and not I guess would be food, temperature and maybe the amount of oxygen in the water (this could partially be from high temp. and I do not have a test kit to test this.)

Reading back over your post, I just realized that you gave us the parameters of your tap water and not your tank water like I thought.

The only thing that changes in water parameters seems to be the Ph but I will test again and let you know.

I will also test my 10gal planted tank. It is in a cooler area and is planted.

I really doubt any specific brand of fish food is going to be the cause. Maybe if we were comparing the effects of really different foods like flake, frozen, etc.. but even then you'd have to be starting with very soft water that easily accepts ph changes to see anything.

Did you take all tanks down for awhile and just start back up? The local water parameters could have changed just enough recently to allow a ph drop. Especially since you only say the kh is low. That could mean it was barely above 2 and now it's 1 or less. Might be enough difference to allow the change. Also double check the kh on any tanks you have setup.

I suppose temperature could have some effect. At the least it would increase the rate that waste and food breaks down and the amount of waste and co2 the fish excrete. It would also lower oxygen levels and increase co2. That increases acidity. You might have been walking a fine line in the past and with the low buffer the minor changes are enough to upset the balance.

I've used baking soda before but it has never been a necessity. Gonna have to go out and buy me a box. Thanks for the info. sham. Now at least I know the food could be at least part of the problem.

I think your right here, the KH is probably just a little too low. I have been testing my tap more frequently tonight and with multiple test kits and it does seem to be slightly lower than it used to be. It's so hard to tell sometimes with these kits.

I have some test strips and the KH in tank and tap looks below 40ppm. GH from tap looks between 25 and 75 and from tank looks between 75-150. Ph looks about 6.2 and from tank and 6.8 from tap.

I tested the Ph, GH & KH over and over afterward with some liquid test kits. GH & KH would change to the end color at the first drop and Ph from tap looked like it was above 7.0. These are old test kits too, so I don't know how reliable they are. I used the strip again and and it seemed a little lower. So not only is the KH low, but i think it is dropping lower.

These test kits suck.

My 10 gal planted seems to have even lower KH and I add a large plastic cup (about 3 cups) of water everyday to top it off. It sits under the AC vent and causes it to evaporate more.

We have water restrictions here like many other areas. Maybe this is partially the cause.

Added just a little baking soda to the tank and will keep adding gradually to bring up kh. This will be a temporary solution until I get some better substrate. Seachem used to have the Onyx line which buffered the water. Never got it because I put a pause on some of my plant growing.

I just caught your reply in the pH thread a few threads down, and it's obvious that you know a good bit about tank chemistry, so you probably already know most of what I described. Sorry if most of it is redundant.

I have to read over some of that information you give a few times. Every time I read it, it makes a little more sense than it did before. They reason I come to these forums. Been running around looking for answers so sorry if I did not get to answer all of your questions yet.

I have been doing a little maintainance on the tanks. I just emptied the 75gal and put my giant gourami (white and pink - should call it a flamingo giant gourami) in the 120 now with 2 severums, 2 chocolate albino plecos, 2 SAE, 1 blue gourami and 4 clown loaches. The Giant Gourmi (about 14 inches) was alone in the 75gal until it got older and less aggressive. Well maybe no less aggressive, it tries to fight me through the glass all the time but ignores the other fish. All other fish are 5-8 inches or less. I have another ~20 gal with another a breeding pair of severums. I also have a 10gal planted with guppies, 1 tetra and 1 scissor tail rasbora.

All seem to have the same Ph and kh problem. Even the 75gal that I just emptied.

All tanks have been up for more than a year except the 20gal which is a couple days old.

Thanks to both of you for the help.

If they're old test kits, they could be quite inaccurate.

I have a suggestion: if you have a pool store nearby that can test pool water, just bring them about a pint of tank water and a pint of tap water. Usually, the higher end pool stores will have actual titration units set up for GH and KH (but they will probably be referred to as Calcium Hardness and Alkalinity, respectively), so they will be much more accurate than test strips and even probably your liquid kit. They can also test for pH. A few of the tests they have aren't going to be worth much to you, like free and total chlorine and cyanuric acid, so just ignore those.

I guess I might have gotten a little technical in my first response. Sorry about that. I'll sum up: low pH comes from H+. H+ comes from CO2 and from the conversion of ammonia to nitrite and then nitrate. KH refers to how many buffer molecules you have. Lots of buffer molecules means that you can control how much H+ is in the tank. Not a lot of buffer molecules means that you'll have a lot more H+ floating around, so your pH drops.

The reason I was asking about your tank size and inhabitants was because of the ammonia --> nitrate. If you were really overstocked, you'd have lots of ammonia being converted, and that means a drop in pH.

I asked about how long the tanks have been up because of a phenomenon known as Old Tank Syndrome. That article is quite an interesting read, although there is one error in it worth mentioning. It talks about a low pH keeping ammonia in its molecular form (NH3) and high pH keeping it in its more toxic ionic form (NH4+). They should be reversed. Low pH = ammonium, which is less toxic. High pH = ammonia, which is more toxic.

Seems like you're on the right track with your KH raising. I hope that that will bring an end to all of your problems.

I'm off to a doctor's appointment right now, so I'll write more when I get back.

Edit: Okay, back from the doctor's office.

Test strips are pretty much useless. If you test the same water three times in a row with test strips, you'll probably get three different results. There's just too much that can go wrong with a strip; it can get wet in the bottle, it can get too hot, there might not be an equal amount of reagents on the pads...all sorts of things which make them about as useful as turd-flavored gum.

Well, I can say that your 20 gallon with the breeding severums (I'm assuming that they're full size) is pretty overstocked, so all that ammonia is going to lower the pH. It seems, though, that that may work in your favor -- I checked the severum's profile on here and it says that a very low pH (~6.2) will entice them to spawn.

I can't really comment on the 120. I have very little experience with large tanks, although what holds true for small tanks should hold true for larger ones.

One thing that doesn't really make sense to me is your 10 gallon. Your KH should be going up if you're adding all that new water. When water evaporates, it is just that: water. It leaves everything in the tank behind (this is discussed in the Old Tank Syndrome article). So, if you have a gallon evaporate, the 9 gallons that remain should, in theory, have the same KH as it did when there were 10 gallons. Even though you're putting in water with a quite low KH, over time the KH should still go up unless you're doing massive water changes every week.

Anyway, let us know how the baking soda is working.

How often do you do water changes? I had the same problem because my tap water was kh=0. When I increased my water changes to 50% 1x/week it solved the problem, because I was removing enough of the built up acids and waste causing the acids that it would be stable at my tap water pH. Now I add baking soda to increase KH but that's mainly because I'm keeping different fish now. With a 50% water change every week, after one month you have basically almost replaced all the water, thereby not leaving enough time for things to build up and drop your pH on you. It's healthier for the fish anyway. Really really good gravel vaccuming is good too. Incidentally this also solved my extreme algae problem.

Interesting indeed!!, been having similar issues for a week now myself, the PH would fall rapidly from 7.2 to 6.flat in a few hours after a water change or a top-off. first visual indicator slight haze in water, 1 hr later FOG...tested tank water (NO3) less than 20ppm, NO2 0 ppm, total hardness 0 !!, buffer capacity 0 !! and PH sinking like a rock. I drained a few gallons and did a partial water change, but added alkaline buffer through the power filter, little risky yes, but effective... 20 min later, water crystal clear, tot. hardness is 125ppm, buffer capacity back up to 180 ppm ( test strips are Mardel) PH is 7.2 and holding...
The only thing that I have done different, is I had to substitute my water conditioner, LFS sold out of my regular formula... bummer, never had this prob till I used this "other" conditioner.... hmmmmm
maybe a connection ????

Hi,
If you want to raise your Carbonate Hardness (KH)
which is a measure of the buffering ability of the water,
simply add some Arm&Hammer Baking Soda. Use only pure
baking soda, with no additives. It easily disolves, and
will affect only the KH of the water. Most would prefer
a KH of 3 so shoot for that as you add the baking soda.

99% of the time, the only additive that is necessary is
a simple chemical that will remove the chlorine and
chloramine. You don't need all those other additives
and they can only complicate what should be a simple
problem - getting rid of the chlorine and chloramine.

I use a product called "Start Right" put out by Jungle.

Frank


-->>> The Confidence of Amateurs, is the Envy of Professionals <<<--

thats what I usually use, the granular form, sub'd with the liquid, did little test with tap water, addded a dash of baking soda to 2 cups of tap water, total hardness was through the roof, added the liquid conditioner, hardness crashed, PH crashed,...buffer capacity crashed, bottle now down the drain......granular is back in stock...

If your pH is below 8, adding baking soda will likely increase your pH too. This is why it's good to only add a little at a time until you are used to knowing how much to add.