Originally Posted by kathateria

I had this.
Lots of oxygenator plants is what you need.Also,buy a bag of watercress,and throw it in.It will root itself.It will use up excess nutrients.
I changed alot of the water in mine too. Compost will make the water green,could any soil of fallen in?It did in mine,as I was doing alot of weeding. I scooped it out,and its definitely the problem.