I have had two remoras and I agree not at all suitable for anything over say 40g. I had the MJ on my first remora which was on my 29g and did a pretty good job. Then moved it to a 55g where it did Ok, but nothing like it could have.
I currently have a remora on my 40b and it has a rio pump on it. It works ok, but if I had the room for an in sump skimmer I would jump on it. lol I am only running a 10g tank as the sump and the room is just not there.
180g- Mostly BIG fish and some coral. ~80g Nuvo- My coral tank with "happy fish"~ 90g- FOWLR Not the not happy type of fish~ 125g- Freshwater Malawi Cichlids ~10g- Nuvo- The refugees from the Ich of '18