heres an idea. sell some of your expensive tangs and fish and use the money to buy a powerhead and a a phosphate reactor. with your lacking waterchange schedule i would recommend 4 maby 5 fish. get a clean up crew, no 1 hermit isnt a cuc. get like 20 snails and 15 hermits for a start and see the outcome. like fast said the algea wont leaver overnight. after these things are done then get more rock. theres no sence in getting more rock right now if its gonna get covered by more cyano. waterchanges once a week till you get parameters acceptable, get rid of fish, more flow, and cheato. i understand its hard to come by money when your a kid( im only 15) but if you cant pay for it sell your tank! its not an easy hobby to be involved with and if your not doing things properly your just killing and hurting expensive fish.
