What causes Diatoms in established tank
My tank has been up and running since March 2012. I started with a 55 gallon. In January 2013, I upgraded to a 75 gallon. I transferred existing sand, rocks, filters etc to the new tank. The only thing that was new was the water!
About 2-3 months ago I stared getting brown algae on the glass and rocks. It comes off easily with a good scrub brush. I'm assuming its diatoms, but seems unusual since my tank is not new. Any thoughts on why this is happening? Thanks.