OK so I just picked up a 20 gallon long planted tank with 10 Serpae Tetras and 2 Otos in it. It had been established for 3 months but had green water when I picked it up. We drained it for transport and when I got it home the water was a much darker green. I filled it back up with treated water. That was almost a week ago, and it is still green though not as dark. For the past couple days I have been doing 25% water changes daily to make the water clear. I just tested it with an API Kit I just bought and read 6.6 Ph 0.5 ammonia 0 nitrite and 0 nitrate. Any suggestions/ what am I doing wrong?