Originally Posted by ChicagoPete
Try Tetra Algea Control or leaving the light off on the tank I know others say they don't recomend chemicles but a year ago when I had my 30 gal community tank I had the same green murkey water problem and that stuff reely helped clear it.
When you kill the algae the chemicals will also kill plants and you must be prepared for a LARGE nitrate spike from the decaying algae.
Don't be afraid to lay your media aside and run the tank for 24 hours with no actual filtration.
If your tap water is very high iron (stains in sink a day after scrubbing, etc) you may want to use mixed dry buffers and distilled or RO water. Plants love the iron and it seems like the water you're adding is making them go ape.
One option if the tank ONLY holds your betta and a bio filter is simply to take the carbon and bio media out, put your betta in a temporary home and drain then fill the tank with straight tap water to give it about ten hours of self-cleaning time. You can then add the water treatment to the tank, count to 3600 then put in the carbon for another few minutes. This lets you return to normal bettakeeping the next day without using noxious chemicals on Das Uberpheech.