My tank glass and the crushed coral on the bottom are getting covered with brown alage. When I siphon some of it comes of the crushed coral but some just stays, and the glass gets recovered everyday. Is there any product that will take care of this?
It sounds as though your tank is not healthy. What are your numbers, nitrate, ammonia, nitrites. What kind of filter do you have? What are your maintainence routines?
How old is your tank? I'd guess it's been set up for a while and you're starting to see the ill affects of the nitrate build up in your crused coral. IME crushed coral causes to many problems in marine tanks to ever warrent it's inclusion anywhere except for maybe a ca reactor. I'd take a h20 reading as tab said and then take temporary corrective actions while you replaice your c.c. It will be a big pain but, IME it's the only way to prevent long term issues with your critters health.
hth
chris