OK, i have a 30 gallon tank with plenty of live rock at least 20 lbs. Two clowns , a Foxface Lo and a lil goby running around. Inverts are just two crabs and a large Turbo snail, I do have an anemone and a cluster of mushrooms, Being with all of that and that i do run a 350 magnum filter with a protein skimmer how often should i be doing water changes, i have been using phosphate pads in my canister filter that has been helping alot but i still get a green algae that will not come off the glass unless scrapped off with a putty knife. Pretty sure this is the cause of not to many water changes. What do ya think??!!