.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 ????