this is just my personal experience but Ive kept 3 gsp together for about 3 or 4 yrs now, right now there are in a 55, but when i first started brackish it was in a 20ga long, with 2 fingers(mono sebae not mondactylus argentus, sebaes are a little more "taller")3 scats a knight goby, and an archer, talk about a can of sardines! anyway, im down(diseases, i was a little lazy at first.....im really sorry fish!) to 3 gsp's , archie, and 2 scats....oh yeah there are the 3 or 4 elusive guppies that are too quick for archie, the puffers dont even pay them any attention! sl that just goes to show that just because a species is listed as "aggressive" or needs at least "100"gallons that doesnt make it the rule! every fish does have its own personality and its own little habits they really are like people. knowing what i know now about fish however i can tell u that overstocking is mean. everything needs a little elbow(or fin) room. i like the sandy substrates, myself, and if you really want, mangrove shoots will grow in even full sea water, they do get big if you dont prune them, rule of thumb is 1 leaf per plant in the tank. and i think the best thing for the puffers is plenty of things to explore, like caves.