Hi
leck85
Please don't let some of the previous responses sour you away from a great wealth of knowledge on some wonderful fish. I'm sure folks were trying to direct you to a good source of info that they themselves may not have been able to provide, but as pointed out, you have already found a good source right here.
As a bit of a puffer nut I have read quite a bit about any species of puffer I can, but not having kept Figure 8's myself I can only give you what I have learned so far (I'm sure you will be hearing some first hand info from Fig. 8 keepers soon).
The Figure 8 puffer
Tetraodon biocellatus is generally considered a Brackish water species, the reason I say generally is there are still some who swear they are a FW species. From what I have learned so far the
Tetraodon biocellatus live the bulk of their adult life, in the wild, in waters with a Sg of around 1.005 (which is low end Brackish) and migrate upriver to FW to spawn. The fry are born in the FW rivers and streams and as they mature they work their way back downstream into the BW. Most of the original specimens collected were juveniles so of course were collected in FW, which led to them first being identified as a FW species. Since that time most folks are starting to agree to them really belonging in BW, due in no small part to dedicated aquarists who have reported keeping Fig 8 puffers in BW tanks for 15+ years, while I have yet to hear of one living in a FW tank for more than 5 years.
As puffer species go, the Figure 8 would IMO rank at the lower end of the scale when it comes to aggression, but that being sait they are still puffers and are NOT recomended for a "community" tank. Puffers will for the most part only eat live (or frozen) foods including anything with a shell. Their teeth (really bony plates) are designed for chewing through clams, shrimp, crayfish, muscles, cocles, etc. and because of their specialized teeth they MUST have these shelled foods or their constantly growing teeth will eventually interfere with them eating and will have to be trimmed manually (this topic I'll save for later). With teeth made for chewing shells even a little nip could be devestating to a tankmate, which is why they are usually recomended for species only tanks....well that and some of them can get nasty at times. Each puffer has it's own personality, from wuss to psycho, and everywhere in between.
The Fig 8 puffer will get to about 3 inches in size, but they are a messy fish (as are most puffers) that create a large bioload in a tank. The usual recomendation for Fig 8's is 20 gals/puffer, but I have read of folks keeping 1 in a ten, but that was with twice weekly water changes. Fig 8's are fairly tolerant of any Ph, as long as the water is fully cycled and virtually chemical free (puffers are scaleless and highly sensitive to ammonia & nitrites). For adding "a little salt", this is another thing about some lfs that burns me, vague instructions. You really need to use a marine mix, rather than aquarium salt, for the added minerals and stuff
that the puffers need to help process oxygen (for a better explanation check with some of our BW fish keepers) and you will need a Hydrometer to check the Sg (around 1.005 is most often recomended). And lastly as to breeding posabilities, good luck, there are no differences between male and female Fig 8's that have been confirmed to my knowledge. You may get lucky and get a breeding pair (I'm sure the puffers can tell the difference) but the fry are norotiously hard to rear due to their tiny size and trouble finding small enough live foods.
Well I have blathered on long enough, but as a puffer owner I highly recomend setting up a puffer palace of your own and getting hooked like the rest of us.
HTH
! And I have to agree with MAM that you seem to always be advertising the puffer forum. Sorry, and I'm not trying to bash you 
but give constructive critism to stop you getting flamed maybe later on. 
