I don't any experience with Jack Dempseys, but you still need a filter good enough to handle the bio load. Jack Dempseys can get pretty big, so a good filter is a must. Canister filters work the best for me, and you can diy a different outflow that can reduce the current. I've got a 7" Red Oscar in a 90g with a fx4, and that filter has a lot of current, enough that I was worried that it was too much for the Oscar, but she's fine. I'll have to fix the outflow eventually, but she seems fine for now, and at her size she's a lot stronger then when I first got her. You can get a lily pipe, but at the size and activity level of Oscars then glass is not a good idea.