I've been having some problems with cyano lately. I'm 99% sure it's because my blue devil damsel digs in the sand constantly. He shakes his tail to stir up the sand and then eats the pods that are kicked up. Then at night he digs a hole to sleep in. The cyano is mainly right at the spots where he digs so I"m thinking he's just stirring up stuff from my DSB. I guess the only solution is to get rid of him.