.started a 75 gl fish tank with dead crushed coral on bottom on left side of tank i put a 20gl bag of live sand and on right 20 lbs live crush coral. . a week later i bought a damsel and add it to it for cycle and a small live rock.now i got brownish algae on the bottom little bit on the filter extensions and couple 2 inches spots on the back glass. i left the light off for 24 hours but it didn't help. i think i give little bit to much to eat the flakes they gave to feed the damsel. what should i do ????
Since you are just starting out remember only bad things happen fast in saltwater aquariums. It sounds like a great idea to put a fish in the tank to cycle it fast until either the fish ends up stressed out and gets ich that can mean an on going issue with the disease or the better case is the fish thrives and decides it wants to be an only fish in the tank and beats up any fish that you put in. The best case is the fish only gets mildly aggressive towards your other fish and you have to take out all the rocks and things to get the fish out. I am with mr x here get rid of the damsel and cycle your tank properly.
Another thing is as your tank matures you will have all kinds of milestones with algae of all sorts maybe not all but you will have an assortment.