green algae

[DavidZ]

What kind of plants do you have and what do you use for light?

 

[DGalt]

I would suggest a black out. Do a large water change and then completely cover the tank so that absolutely no light gets in. Wait 72-96hrs. Leave the tank alone (no feeding, no checking in...fish will be fine for 3-4 days).

When you open the tank back up the algae should be dead (hopefully). Then do another water change to remove the dead algae

 

[DavidZ]

Sounds like it would be easier to add more low light plants