clean-up crew

I haven’t really had a need for a CUC yet, but I’m getting worried as to what I should put in. Any suggestions for a CUC for a fluval seaevo 5 tank? Tank is below.

Hello everyone! Everyone was very helpful with my first post, so I'd like to thank everybody who responded. Onto the main question, my 10x20 tank (10 gal, no sump) has just gone through a diatom bloom (it's now beginning to retreat/hibernate). I read somewhere that this means your cycle is...