The 20. I had to wait on the light it has on it now,and in the meantime had a HO T5.I did not have any CO2 hooked up to it(my bad) and black hair algae started to grow. I got the new light for it and started CO2. The algae has seemed to stop spreading,but it is still there.
I can't add anything to eat it.The tank,and all my tanks are fully stocked,and then some.
I was thinking I heard somewhere that dipping them in hydrogen peroxide will kill it,but I'm not sure if it works or exactly how to do it.
I ordered new plants for it,but with all the cold weather this week,they weren't in very good shape.So I am hoping maybe I can get the algae off the old plants,if the plants I got this week don't make it.