How big of a tank should I go with for officinalis? Would 75 work for two? Would it be reasonable to try officinalis with bandensis? Same questions for pharaonis. I would guess pharaonis would be better off in this situation due to the fact that it's a warmer water ceph and doesn't necessarily grow as long. In the off chance that I do keep either of these and they do outgrow the 75, I have a 100 gallon stock tank attached to the system that they can go into.