Reasons for Low pH?

[Maritess]

I have had some fish die on me recently: in a fifteen-gallon tank there were some female betta fish, neon tetras, and some platies. They seemed to get along fine, but all the platies and a couple of the tetras died. So on a whim I bought some pH testing strips. Apparently my water is pretty acidic (about pH 6). After a major water change, and adding some chemicals to lower the pH, a day later the water is still testing about pH 6.

Any ideas why my water is so acidic? Do I have some excess food decaying or a dead fish rotting under in the gravel?

Suggestions??

[PPulcher]

After a major water change, and adding some chemicals to lower the pH, a day later the water is still testing about pH 6.

If you are adding chemicals to lower pH, this is part of the answer! Driftwood, peat, oak leaves and decying food/plants can also reduce pH.

I suggest that you test your tapwater before you put it in the tank. Let water some sit in a cup overnight and test it the next day. This will give you a more accurate picture of your water as there won't be excess dissloved CO2, which will make the pH lower.

Another thing to consider is testing the alkalinity of the water. This is also known as carbonate hardness or KH. Very low KH values can't buffer the water very much, leading to very low pH with the acids produced by your filter bacteria and other biological processes.

What might be happening is this: consider that ammonia is much less toxic at pH values less than 7 (neutral) as it is in the form of ammonium. If your tapwater is alkaline, doing a major water change can bump the pH above 7, where suddenly the ammonium becomes ammonia and we know that it is toxic to the fish! I think it's called 'old tank syndrome' or something similar.

[_Aaron_]

I would suggest not putting any chemicals in that adjust the PH.

Your water should be fairly close to neutral right out of the tap.

[GaryofMontreal]

You really have to check your tapwater. Mine comes out quite acidic - ideal for rainforest fishes but not great for livebearers. In my old house 10km away, I got alkaline water that nothing would acidify. Even within one region it can vary - downtown montreal stores the water in limestone reservoirs while the suburbs use neutral water-tanks. I have friends in NB whose city offers alkaline water on the east side and tannin stained acid water on the east. Check your starting point.

[firestorm]

Decaying and rotting material can be a cause to why the pH can lower as well. Doing more frequent and larger water changes can help to keep a pH stable, especially where your tap water does have a lower KH. And having more fish can cause more CO2 in the water which makes the water more acidic. I think you might have old tank syndrome as well.

PPulcher is right on the money though.

[Melody]

Much of BC's water comes out of the tap at neutral and is very soft as well as low in KH. However, the fish you have should adapt to that easily, especially the Tetras who love acidity, so I think you have another factor there. Be sure to vacuum your gravel well and cut the feeding back sharply - way more fish die from pollution than starvation. How many fish exactly were in the tank?

Definitly leave the chemicals alone for now and try to find the cause of the change.

[Trouser Trout]

I have the opposite problem, my pH never drops below 7.6, which is the highest the scale goes on my test kit. Tried tablets to bring it down, but it does not seem to make a difference. What can I do to make it a little more acidic? Should I even worry about it?

[CACAdmin]

If your fish are fine with your current pH, I wouldn't worry about it. Otherwise, if you wish to lower pH, you can add Indian Almond Leaves or driftwood.

[_Aaron_]

I have the opposite problem, my pH never drops below 7.6, which is the highest the scale goes on my test kit. Tried tablets to bring it down, but it does not seem to make a difference. What can I do to make it a little more acidic? Should I even worry about it?


I wouldn't worry about it.

[Melody]

Some fish will want a lower pH to breed but otherwise I wouldn't worry about it either. Fluctuations will harm them more and it's hard to lower the pH without fluctuations. You can make it more acidic and keep the KH occupied with peat moss or whatever, but you can't remove the hardness to any great degree (although I'm told that carbon will absorb some). The only consistent option is diluting it. I'm sure you'll be fine without going there.