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?
I had experience with diatoms with my established tank. I was running top soil under silica sand and people were convinced it was my sand. But I tried many things to remove it, even purigen and it was temporary...
I noticed that in the shadded regions of the tank I didnt really get diatoms to show up, but in the areas where light was hitting I definitly got them. Tom kept saying its something with the co2 and light. So I bumped the co2 and noticed no changes. Then I decided to turn off one of my t5ho's...low and behold the diatoms started going away.
Till this day, I dont have any diatoms with my silica sand.
Did you disturb the substrate? Released ammonia from substrate is often the cause. After every re-scape, you need to change at least 50% of water.
Secondary, diatoms are often in tanks with too much light and not enough CO2 supply. So cut the lights down or increase CO2 supply (or both).