I am having a serious problem with green water in one of my betta tanks. It started when I added a moss ball - people have told me it can't be related but it sure seems to be.
In any event, it's a 5g minibow with a 7w corkscrew light that is not on very often. No direct sunlight and not much ambient lighting. Not overfeeding. There is 1 betta and 1 nerite in the tank. Live plants are a java fern and some duckweed. I've been doing alot of vacs and it looks better for about 10 minutes and then it's green again. It seems to be getting worse

Not sure what to do here. Do I have to do a blackout? If so for how long? I hate to do that to a betta as they are so personable and friendly. I guess if that's my only choice then I'd move him to an empty tank while I do it so he doesn't have to be involved in the process.
Any suggestions? I just can't figure out why this is happening. But I added a moss ball to each betta tank and now one has green water and the other has an outbreak of algae that looks identical to the moss ball (I do know they are algae and not a true moss). I got rid of them but the problems persist. I never ever had issues with these betta tanks before this. Grrrrrrrrrrrrrrr!