I always thought that pea gravel was inert, but after reading this article
it appears as if though that is not the case, and that standard pea gravel has enough calcium to boost pH and water hardness. This is of concern to me because I keep softwater species such as cardinal tetras and otos.
I've tested the pH of both the tank water and tap water using a liquid test kit (only option I have), and they appear to be around the same, with the tank water possibly being slightly more basic. Both are between 7.2 and 7.6 (around 7.4), and if there is any difference in pH it is very small. Is the small difference due to an insignificant amount of calcium in the gravel, or due to the age of the gravel, meaning that any pH boosts would have occurred already? Or could it be from other factors, such as decaying plant matter or the many vals I have in the tank using carbonates from the water? Also, the test was conducted an hour or two after the lights had turned off.
I have two types of gravel in the tank. The first type is white and brown pea gravel I put in the tank when it was first set up in 2003. The second is some Petco brand black gravel, which appears to be colored with the actual gravel being white. The black gravel was put into the tank two years ago.
I had originally put in the black gravel to cover up the lighter colored gravel, but now after pulling out a good amount of vals with established root systems, the white gravel is starting to show again and I am thinking about adding some more black gravel to cover it up. I am concerned that if I do so, the calcium in the new gravel may cause a pH boost detrimental to the fish. Am I being overly paranoid, or is that a real possibility?
Thanks to those who have read this far.