Ph General Questions

[pkppv]

I get ph and buffers from a chemical standpoint, im quite good at chemistry, all i ask is your expert advice on pH from an experienced aquarists point of view.

How important is pH for fish?

Why would my pH be higher (or lower) in my tank than in my tap?

Similar question: Why might my pH vary tank to tank?

Whats a general acceptable range?

Should i be concerned about a pH of 7.55?

Should i want to change it?

Thank you all so much, i must have set a record this week for questions, but i just want to know the most i can and be the best fish owner around!

 

[onidrase]

How important is pH for fish?

It's most important that the pH doesn't fluctuate a lot. Though some fish prefer a higher or lower pH than others, it's most important that the pH stays constant.

Why would my pH be higher (or lower) in my tank than in my tap?

Some substrates and decorations will buffer or lower the pH, though usually they'll advertise such, so it shouldn't matter.

Similar question: Why might my pH vary tank to tank?

Different decorations or substrates

Whats a general acceptable range?

Depends on the fish

Should i be concerned about a pH of 7.55?

Depends on the fish

Should i want to change it?

Nope. If you want a higher or lower pH, look for stuff that stays in the tank that does it naturally. Really, those pH up and down bottles are totally useless.

 

[OldMan47]

Let's go really simple here. You do not care what your pH is as long as it is not too extreme. I will take your word for it that you understand chemistry. When you add an acid to reduce the pH in a tank it does not accomplish what you want. Instead it raises the mineral content of your water by converting bases to salts while adding whatever minerals are involved in the acid itself. Fish care is simple and what we know about fish needs goes way back several decades. At that time it was easy to measure pH but not as easy to measure mineral content of water. It was also easy to measure GH at that time. Since certain fish were often found associated with a particular pH, it was assumed that they needed that pH. More recently it has been found that total mineral content seems to impact fish more than pH does. What that means to us is that the increased mineral content that results from lowering pH has exactly the opposite effect to what we tried to do for the fish has backfired.
Fish from naturally low mineral water are being exposed to even higher levels because of the chemicals we have added to lower the pH. If I want to keep fish that are picky about having low pH I use pure water, in my case RO water, to dilute the mineral content of my tap water. The pH does not change at all but the water has a lower mineral content than I started with and the fish thrive.

Why does the pH of a tank differ from tap water?
Tap water has CO2 dissolved in it. When you release the pressure on the water, the CO2 comes out of solution and the pH rises. Now you place a biological load on the tank and the pH goes down because the form that the nitrate in tank water takes on includes nitric acid. You have gone from having ammonium hydroxide, a weak base, to nitric acid, a strong acid, dissolved in the water.

Any pH from about 6.5 to 8.0 would be fine for most fish as long as the mineral content of the water, expressed as TDS, is close to their native water.

 

[pkppv]

Thank you very much oldman47. Now i know all i could ever want to about pH! haha