I use two hides in all my tubs, but as was mentioned, a lot of breeders use the rack or an opaque tub to serve as a hide. Either can be done... but I can tell you that they use the hides (both) in the tubs that I use... so they must like them. 15qt tubs with two hides and a water bowl makes it pretty cramped in there... but hey... small spaces.. happy balls!