You can relatively divide a 55-gallon aquarium using egg crate lens material cut to fit. I would divide tank in half. To suppress social problems, stock more bluegill. I can keep forty 4" BG in a 55-gallon assuming aggressive filtration and frequent water changes. Keeping density high will suppress breeding issues when temperature maintenance for anglefish realized. Bluegill will get urge to breed even during winter if temperature and photoperiod appropriate.
