I have a brownish algae growing on my tank walls. I was told that these are diatoms. I was wondering what is causing this problem. Could it be a seasoning problem with my tank (2.5 months old)? I change my water twice a week (25% & 50%). Could this be the reason for the inbalance, causing the diatoms vs. green algae? It was suggested to try reducing the frequency of the water changes.

Any suggestions?

You can do several things.
One you can get bighter lights
two dont have your tank lights on as long.
Three Us Phosorbe this will help with the Diamonts.