in my opinion, you can change the water till the fish come home, that wont take care of the alge. do you have anything that eats alge? if you can get one i would. you know how i feel about chemicals(everyone knows how i feel about them) but it might be an inbalance in the water causng the alge, not the fish. there are all kinds of chems. from 'jungle' that takes care of a lot of problems. however, once you medicade your tank, you could lose fish. ive never had that happen with 'jungle' but there is always a chance. my bala had the white fungi on one of his eyes and the only way i found to get rid of it was the fungus clear from jungle. it turns the water a beautiful emerald green, and within 3 days his eye cleared up.( the green color looks great with the flo. lights.) sorry moment.
. i will look it up in a book i have and will let you know what i find.