Right now I have several parachomris growing out in a 40 g dovi is about 3" livig with a 3" jag a 2.5" loiselli and a small dovi and another small loiselli. The dovi is boss but rarley attacks or injures tank mates. He only has a tiny bit more of growing to do before I move him out. I don't see any problems with a jag and dovi in a 180 if both bought small. Just add a few dithers like cons or even some danios to distract them from one another.
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No offense, but you can't compare how well a dovii will do with tankmates at 3" versus the strength, speed, and domination they will have starting at around 14". A dovii will probably be very docile towards tankmates until he hits that magic mark. Then all bets are off.