+1 to this
I started with chaeto on my HOB fuge, got sick of tumbling and trimming. When i slacked like this the chaeto started dying, flowing in the tank, etc. Then I figured out, after researching, that chaeto for a smaller tank in an ac70 sized fuge is like using a match against the sun in a firefight. You need a large space like a sump refugium to properly do the chaeto nutrient export method. It needs to grown and then be trimmed to successfully export the n & p, if it is not then it starts to die and you will end up with more n & p then you had in the first place!
So I ditched the chaeto and now just run small DIY reactors (rowaphos & zeovit carbon) in the AC70 with a lot of success. In conjunction with a DIY skimmer, I have all the nutrient export I need outside of PWC's.
I also keep some blue macro algae in a onion bag in the tank, it performs some of the duties the chaeto did before.