Why is a low pH level bad for fish?

Answer 1

It shouldn't. A pH of 5.5 is much too acid to keep tropical fish. The only fish that will survive at this pH are species that are specifically adapted to very acid water, such as chocolate gouramis and some tetras. If you want to keep tropical fish, you will need to buffer the pH by adding something like oxy blocks to your water.

Answer 2

A low pH level means that the water is acidic. The main thing to understand is that not all water is equal. Different water bodies (rivers, lakes, etc) have different water chemistry, and therefore a different pH. So various fish species have evolved to live in water with various pH levels. There are fish that are most comfortable at around 6.4, fish that are comfortable around neutral, and fish that are fine living in water as high as pH 9. So it's really a matter of doing your research. If you have acidic water, it's a lot easier to choose fish that are already adapted to living in this sort of water (like tetras, barbs, rasboras and corydoras catfish) than to try and adjust it. A low pH level is only bad for some fish.

Answer 3

7.0 means your water is neutral rather than acidic or alkaline. If the pH is higher than 7.0 than your water is alkaline and a pH lower of 7.0 is acidic. The pH shouldn't be 7.0 for all fish, For Freshwater Fish the pH should remain constant and Saltwater Fish should have the correct pH there species prefer. Some fish need the water acidic(lower than 7.0) and some fish like the water alkaline(higher than 7.0). So it shouldn't really be 7.0 it should be what the species of fish prefers but it is often around 7. It doesn't matter if the fish is tropical or not, Tropical Angelfish prefer the water more alkaline and other tropical fish prefer it more acidic.