I see the picture and clearly say that it's an algae bloom. We get algae bloom when we feed excess food (excess nutrients in tank) and if there is a direct sunlight falling on the tank. First of all get a pleco (algae eating fish) one or two. And some nerite snails. They will help clear your water. Don't do water change as the algae will grow again in few days. Don't use any chemicals. Use a good filtration to clear out algae from the tank.
Hope it helps.
Hello; I do agree it looks like an algae bloom. I also can see overfeeding as a contributing factor.
I do not agree with getting a pleco for algae control. Nor Chinese algae eaters either. The small ottoclincus (sp) may be decent at algae control. A common pleco can get to well over 14 inches and are very messy fish. Only reason I see for getting a pleco is if you really like a plecos.
Nerite snails are good in a tank and will eat algae on glass. Not sure about the free floating algae in water.
I do not agree with avoiding WC's. First WC is a tool for keeping water quality good and second removal of some of the algae dose not hurt. If excessive nutrients are the root of the bloom then yes the algae will continue to reproduce, but my take is they will reproduce anyway.
I do agree with good filtration and lots of WC. Change out the filter media often as well.