I had the same problem with brown and green algae. I bought some snails which helped a bit. then i got some bristlenose catfish, 5 in total. my b/n catfish are still very young (ten weeks old) so they are ok in the small tank i had the problem in but i will have to move some to another tank cause they are getting a bit big.

Snails and catfish both help but also put in some cucumber/peas for a change in diet (my guppies and platies eat cucumber/peas too )

thats my 2 cents

Flik