I started out with 1 female in my 100 liter planted tank. At the time there were ottos, amanos and a few sundry tetras/shoalers. I don't think she ever truly settled and never seemed entirely happy.
They can be very slow, deliberate feeders - so things like live daphnia, frozen bloodworm etc were almost invariably swallowed up by the other fish unless you deliberately added loads... So her staple diet became bladder snails and asellus which none of the other fish would touch. She never to my knowledge attacked any of the shrimp or fish or was remotely aggressive to any of them. Although the flow in that tank was not very high, she didn't seem to mind it at all.
Just over a year ago I moved her into a smaller (35 liter), heavily planted (think impenetrable jungle!) tank with six new puffers and she was a different fish. Far more relaxed and a much better feeder - she will actively hunt down things like scuds (although that may be in part to competition with the other puffers) and spends her days picking through the moss, ferns and floaters looking for food.
The other six grew well and matured around 6 months ago. They started to breed on a semi-regular basis (the group is four males and 3 females). I could never retrieve any eggs as the non-breeding females always follow the breeding pair around and hoover up the eggs so I just left them to it for a few months. There was/is never any full blown aggression - just the occasional sparring between rival males (almost always in the afternoon when they usually get frisky). They remind me more of a group of loaches that are continually jostling each other (though at 10% of the speed). I started occasionally throwing in some low quality, excess cherry shrimp from one of my other tanks and was surprised a few weeks later when I noticed most of them were all still alive. If they were big enough when they went in, they were either capable of evading any interest or just didn't get any interest at all. As you can imagine, the shrimp population doesn't grow though - shrimplets are soon hunted down.
Around October last year I split them up to try and breed them properly. I moved 2 pairs into separate tanks by themselves and left the original female and 2 males in that tank. None of the 3 groups were happy. Very shy, stopped feeding well and generally looked miserable. I put them all back together 2 weeks ago and they've started breeding again...
So based on my experience with this group:-
- treat them as a shoaling fish - probably at least 6. They are much happier in a group and aggression seems to be diffused (although I may just have a docile group).
- heavily planted including floaters and lots a wood, twigs etc
- feed heavily. They seem to lose weight really quickly. (and they love scuds if you have the room to culture them elsewhere)
Personally I'd love to see a bigger group in a 350 liter tank. With the right setup and tankmates they would be fascinating. Hatchets I'm sure would be fine, as would lampeyes/tetras etc - the only real issue would probably be feeding them when having to compete with the faster fish. Smaller shrimp will always be a lottery.
Still in my top 3 favourite species after 25 years of fish keeping.
Regards, Mark