Diatoms in a mature tank?
I have a 90 gallon planted tank (rather heavy fish load) that has been up for over a year. I have been seeing a lot of "dirt" settle on my leaves and substrate and float around the tank. I thought it was BBA but think it might be diatoms. It does not respond to H2O2 at all and rubs off easily with my fingers.
If it is diatoms, I assume this is due to high silica either from my tap or from the rocks in my tank (substrate is ecocomplete).
Does this make sense? Should I take out the rocks? How do you test your tap for silica?
Or am I just waaaay off base here ....