Which one would be better a 6 foot cylinder with 18 inch height or 83x46x18.....I believe the 6 foot cylinder has a better base area
18" will be tough for rays either way, I never thought I would say that for 24" but even that is getting small for the females. Depending of course what species you want to keep. The appeal of a cylinder is there for sure, but I think you may run into issues with plumbing, stands, possibly circulation, I would almost think that going with a standard would be better as no surprises.