Hi, here's The Story Of Sanjay and Gupta (not coming to a cinema near you).
I bought my DP's a year and a half ago. I was initially told by the shop that as I had a 6 UK Gallon tank I could eventually fit 6 into my set up. It's amazing how little even respected fish shops know about their stock. After searching the web I decided two would be fine in my tank, and for a while everything was. The plants grew well and I introduced five little (2cm) amano shrimps to the set up. Several of you may have sucked in your breath and the more sensitive of you may have actually fainted, but despite my naivity and more bad advice the shrimps survived and prospered, even stealing bloodworms from under the puffers noses without even a nibbled antennae to show for it.
Then about 4 months ago things went all Night of the Living Dead on me. The little fellows had always had the odd scrap but things were getting out of control. Gupta had two really bad bites on him. I had another tank on the go (a ten UK Gallon) with some snails in, and the last of the big apple snails I had in there had died recently, so I decided to swap over the livestock. I planted up the ten Gallon, and medicated Gupta's bites. I got most of the Malayan Trumpet Snails out, but one or two met a some what grizzly end.
Fast forward to the present, and both fish are healthy and doing well. I have very little open water, perhaps six cubic inches and a narrow channel along the front, and for fish as aggressive as my pair ( some groups get along fine ), I think the more plants the better really.
As for behaviour, I think that it is important to look out for the fish side by side, flattening themselves into almost a tennis racket shape which is ended by one chasing the other off. If this happens often keep a look out for bite marks as this is often a prelude to fighting.
Whatever you do, don't be put off by my story as they are really great fish to keep, with real character and intellegence.
All the best from Bill