is this Sea Lettuce?

[BryznNguyen]

Is there anything bad about keeping what I think is sea lettuce in a 20g tank? Its growth has kind of exploded inside my tank, one thing I have noticed is that one of my torches arent doing well and one of the heads died but everything else is happy (hammers, frogspawn, zoas, acans, some beginner sps)

 

[Zach B]

Sea lettuce/Ulva can spread very quickly in a DT. I unfortunately know from past experience. It's a great exporter macro for nitrates but takes over fast. Best of luck

 

[Subsea]

Your display looks healthy. The mature corals and coralline algae are already good biological filters that recycle nutrients into their biomass. I second getting rid of Ulva. It would help if you had a tank thread to better understand your system to help better with recommendations