it looks like you have a mixture of cyano
and diatoms there. how did you get rid of the cyano
last time? use a chemical? if so, cyano
is only a symptom of the bigger problem which is excessive nutrients. this must be corrected or it will continue coming back.
i would get on a regular water change schedule using good source water (R.O.D.I.), and possibly cut back on feeding.
what size tank is this? what is your bio load like?