Overstocking is a standard method for diffusing aggression with mbuna, Central American cichlids, mudskippers, archerfish, monos, halfbeaks, and swordtails. I see no reason at all why it wouldn't work with pufferfish. They are, after all, just fish.
The "gotcha" is of course water quality. Mudskippers couldn't care less about water quality (they live in swamps) but pufferfish are comparable to cichlids in terms of their intolerance of dissolved metabolites in the water. So as with overstocking a Rift Valley cichlid aquarium, you may solve one problem (aggression) while creating another (health).
A lot of aquarists confuse territoriality with bullying. Most cichlids and many pufferfish are territorial: they will actively protect a region they view as their 'home turf' and other fish entering that region and viewed as rivals will be threatened or attacked. In a tank with six or eight fish, each fish has to track and react lots of rivals and finds it difficult to bully one specimen. So there's a sort of Mexican standoff, with the relationships between the fish in a sort of dynamic tension, constantly in flux as the fish move about but never able to settle into a fixed hierarchy.
In a tank with only two or three fish, the strongest fish will be able to become hyperdominant, that is, claim the entire tank as its own, because it is able to spend more time threatening the other one or two fishes in the tank. That's bullying. Such bullying isn't "normal" behaviour and shouldn't be termed as such: it is a function of aquarium conditions. Many species that exhibit bullying in the aquarium form 'colonies' in the wild or even schools (archerfish are the classic example here, schooling fish in the wild, difficult to keep in small groups in aquaria).
There's a great video on YouTube of a school of plecs. In aquaria, plecs are always described as "territorial, one-to-a-tank fish". Quite clearly, they are not so in the wild.
http://www.youtube.com/watch?v=5bK5wg2tZ0U
In other words, aquarists assumptions of what is "normal" behaviour is in many cases simply not the case. It wouldn't surprise me in the least if C. lorteti wasn't relatively peaceful in the wild, where conspecifics could either keep their distance or simply occured in such numbers that tensions were diffused easily. Perhaps the variability in aggression we see in pufferfish reveals differences in how they are kept in aquaria rather than some innate untrustworthiness in their behaviour or genes.
Cheers, Neale
But I've been puzzled by the passiveness. Maybe this is what makes some LFS think that puffers are peaceful fishes?
more girls name than boy... But I'm from Norway. hehe
oh...
