Algae ID

[michika]

Have you tested your phosphate levels lately? Could your phosguard need recharging/replacing?

I battled cyano for a long time in a previous set up and in my case it was the result of phosphates. I was careful to do weekly water changes with RO/DI water, and to use a phosphate remover, like you are. I also made sure to arrange my flow so that there were few "dead spots" in the system.

Try pointing your powerhead lower, but be careful you don't mix sand into your water making everything cloudy. The goal should be to get water movement all over your system. Maybe for now try aiming it at one area, say a particular corner and see if it helps with the cyano you have now.