Puffers are aggresive and terretorial, the guideline says you should keep them in a species only tank, coz chances of them killing off all your other fish are high.
Figure eights are brackish fish and for this reason should not be kept in anything smaller than a 15/20G. Keeping a brackish enviroment in smaller will be pretty much impossible. In 1 15G you can keep 1 figure eight, and nothing else. To keep 2 I'd say you need at least a 30G seeing as in brackish water you wont be able to make hiding places as easily as in freshwater tanks seeing as most plants die because of the salt in the water.
For feeding requirements, well, pretty much anything thats alive or frozen and has enough nutricion in it. Live/frozen bloodworms being the main diet, with treats like mysis, brine shrimp, live river shrimp etc. It will be very important to supply snails and other animals that can be eaten and have a hard shall/protection to keep their teeth down. While feeding this you're gonna have to be careful, because if the shell is too hard (like malaysian trumpet snails for example) it will break their teeth, which will be bad for the puffers health.
By reading this informantion, please do not think you know enough and run off to buy some, but do as much research as you can! Keeping puffers can be tricky, very tricky. They require pretty much perfect water to survive, so make sure you'll be able to give them all needed to keep them alive and healthy.
