I've got a 20gal and had it for 4 months. the tank is cycled and my nitrates usually hold steady at about 20-30. I do 25% water changes probly about once a week, vac about once a month, and clean just a slight bit of slime from the glass maybe every 2 weeks. I've got 3 leopard danio's, 3 red minor tetra's, 4 rasbora's, 1 male guaramis, and a beta all doing very well. I do have the room for an Oto but they're not exactly the most pleasant looking fish and was saving the room for fish i want but you have to do what you have to do i guess. How many do you think you need for a 20gal. That phos-x stuff worked for like a month and then right back to the algae. I only run my light about 2-3 hours in the morning and then about 3-4 hours when i get home from work. I run a minibio and the kit filter.