Acidity that won’t quit

[Joymaker]

I have a 55 gallon aquarium with about 15 smallish fish: most of them are about an inch and a half long, and the 2 largest are a pair of Danios about 4 inches long, so I'm fairly sure my aquarium is not overpopulated. But I am overcome with acidity! I put in Neutral Regulator, a tablespoon a day for several days – pH still reads about 6.4. I try putting in acidifier, a tablespoon a day for a few days - pH still reads about 6.4.

This is getting expensive, pouring in all these additives without much result! What would be a root cause for persistent low pH? (Admittedly, that's about the pH of the tapwater around here, but I add stuff to overcome that whenever I do a water change.) I am wishing that there was something large in solid form that I could put in, that would just keep on buffering the pH back to 7.0.

Product suggestions? Other strategies?

Here's a current reading of my tank:
Nitrate 60
Nitrite near 0
Hardness 0
Chlorine 0
Alkalinity 160
pH 6.2 - 6.4

 

[GaryE]

To me, the best strategy is to enjoy a pH of 6.4. You're lucky.

Other than Danios, most of which thrive at a pH of 6 to 8, what have you got in there that would make you think the pH was problematic? I have tanks with low hardness and acidic conditions, and my fish have never been in better water. I choose rainforest fishes though.

 

[jaylach]

It is usually a losing battle to try to control water conditions to match fish. It is better to match fish to the water.

As a note your nitrate level is way high.

 

[Colin_T]

Limestone, shells or dead coral skeleton are all made from calcium carbonate and will slowly increase the pH of water. You add a few pieces and monitor the pH over a couple of weeks. If it remains too low, add another piece and wait a few weeks. Continue adding and monitoring until you get the pH where you want it (around 7.0 for lots of fish).

 

[jaylach]

Limestone, shells or dead coral skeleton are all made from calcium carbonate and will slowly increase the pH of water. You add a few pieces and monitor the pH over a couple of weeks. If it remains too low, add another piece and wait a few weeks. Continue adding and monitoring until you get the pH where you want it (around 7.0 for lots of fish).

Personally I'd prefer to keep fish that fit the water rather than trying to change the water to fit the fish but I know that some may have a favorite fish that won't go with the water. In such a case I can advocate trying to adjust the water even if it can be a pain.

So actually the above leads to a question... Instead of coral or shells how would cuttlefish bones like you give birds as a calcium supplement work? I mean they are pretty much pure calcium and relatively cheap. Also they are soft and porous in relation to shells so may work quicker.

 

[GaryE]

^^^^^^^^^^^^^^^

That's my diagram of doctored water with shells and calcium. If hardening is the goal, then it's up and down with every water change. It often leads to an aquarist cutting back on water changes, and that leads to fish living short lives.

My question is simple. Why?

I've seen the myth of pH 7.0, which suggests neutral pH is ideal. It's supposed to be in the middle because then every fish is happy. It really doesn't work that way. I'd suggest half an hour of reading before you acquire fish is even better. Choose fish for the pH you have. There are many more wonderful species available that come from a pH closer to 6.4 than there are species from 7.0. Although again, I'd argue that pH is a secondary reading anyway, and water hardness is what matters.

When someone tell me tanks should be at pH 7.0, I know I'm listening to a newcomer to the hobby, or to someone who is stuck at a newcomer level and no longer trying to learn. It's a common statement from trained fishstore people who aren't experienced aquarists themselves. If you go to a shoe store and the clerk says size 7 is ideal for every foot...

 

[Naughts]

I wonder if ‘old tank syndrome’ is also at play here in addition to soft acidic water.
When water changes are insufficient, nitrate builds up and the water acidifies.
The solution is to slowly build up the water change frequency and quantity then continue water changes at this level to maintain the water quality.
You cannot simply switch to 50% a week (after, for example, previously changing 10% a month), though as the pH may jump and harm the fish. Build up gradually to get to where you need to be.