white cotton tufts on sump wall - not the fish

Question
Hi -
I just noticed white cotton like tufts on the first stage sump walls of wet dry filter. Could this have anything to do with excessive lighting, calcium or because my protein skimmer hasn't worked properly for the past week?  My fish, live rock and annenome appear to be thriving and show no signs of this.  Your advise is greatly appreicated.
Jennifer

Answer
These may be the beginnings of a type of sponge. Shouldn't hurt anything. How long has your skimmer been running? It may be time for a cleaning. How are your water levels, ph, salinity, nitrates, etc. Have you changed anything that might have affected the skimmer somehow? Gerry.