The Colomesus asellus are well suited to a 55g tank- and you can keep more than one (with cation)
The dentistry is not hard- ask Pufferpunk- she just walked me through doing it on mine. As far as snails- ask the LFS for them- they will give them (the ones that come in on plants) to you or charge very little (like $1 for 36). Just put them in your tank for 2-3 weeks before getting the puffers and you should not run out (nature will provide). The biggest drawback is finding them. I have looked online but miss out when someone has them in stock every time.
That red one is a Congo Puffer and they can live in a 55 g? Well that just blows my Cuban Cichlid idea right out of the water. You guys are killing me with all these fish that are so cool! I'm going to go look them up.