OK, basically you'll need a bigger tank ASAP. Your going to need about 200-250 gallons for him when he's an adult. However, in a tank this size you can add companions.. things like big plecs, large south american cichlids etc. I have found that Mbu Puffers and Frontasta Cichlids is a nice mix.
Learn to interact with your mbu as quickly as possible. Take your time when feeding him so he comes to reconise you. Then you can make feeding fun (for example putting prawn on the end of a skewer and making him chase it round the tank.) There's no real way to combat boredam about from finding the right tankmates and entertaining them at feeding time. Once you have the larger tank provide plenty of cover in the form of plants and bogwood but also leave loads of swimming room (there is a happy medium). It can be really hard putting a small, baby mbu in a 250 gallon tank with only 1 or 2 tankmates because it looks so bare for a few years, but you really have to imagine their adult size which is huge! Another tip for keeping him entertained is to put him in a room where plenty happens. Larger puffers take plenty of interest in what is happening outside of their tank and this is a good way to keep them occupied.
One quick word about adding tankmates is to be so careful. Every single large mbu is different from the next and make sure you have somewhere to home the new tank mates should the puffer turn on them and visa versa. Some people have had success putting them in a tough, cichlid-like community settings when they are small but equally, some people have never been able to find suitable tankmates for their mbu.
Mainly, give him a name and a personalitity and interact with him the best you can. Puffers, espically large puffers, react much better to a new surronding (i.e. your new 250 gallon tank!) when they are dependant on their owner. It's almost like they think 'well, daddy and mummy put me in here so it must be safe'.
If you can provide the tank size that so many mbu keepers fail to offer then you will get years and years of fantastic interaction with one of the cutest and most loveable 'pets' out there. The mbu is really one of those fish that can be classed as a pet because of the way it reacts to it's owners.
If you can't provide a minimum of 200gallons for it then please find a new home for it as it isn't fair to keep such a wonderful creature cramped up - contact me if you need help finding either a tank or a new home.
Any more questions - just ask!
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