3' bare min. IMO. 4' will be much more comfortable so if possible go with 4'. Look at it this way, as the jag and festae get closer to max size they are going to claim at least half of the tank to themselves. So that either 4x4 or 4x3. In all reality may not be enough but they will probably stay on opposite sides of the tank but will be less inclined to venture into the others turf with the larger tank resulting in less aggression. The aro will hopefully mostly be ignored and the carpintis shouldn't be perceived as a threat so it should also be fine. But no guarantees with cichlids! Good luck.
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