It's also worth noting that (unless I'm mistaken) your system has adequate filtration for cephs, which I bet is a lot more than an off-the-shelf 55 you'd get as a package in an LFS, right? I'm not sure if 3 cuttles would overload such a system or not, but 3 cuttles in a 55 probably will only be safe, or at least ideal, with the right setup.cuttlegirl;92739 said:I would say no more than 3. You will not know until you have the S. bandensis for awhile whether you have males or females. If you have all males, you will have them fighting with each other and they will need to have enough space to retreat after they are finished fighting. I don't know how many Thales has kept together, but he is a special case, with a lot of experience.
I had three (2 males, 1 female) in a 55 gallon with a sump. I personally wouldn't put more than three in my system.