Came back to the store after a week and this is how one of the 55s looks. It had African cichlids and always had green water issues. Last week I did an 80% water change and it looked great but it's back. I'm trying to prep it for livebearers and plants. Currently it just has two large pieces of limestone and a couple of plastic plants. Can I just dose Algaefix and then do another big water change?