Hi, congratulations on your purchase of puffers, they are great.
However, I don't mean to attack you at all but Figure 8 Puffers need about 10-15 Gallons each.
I don't know if you plan on moving them into a larger aquarium or not, but unless they are extremely small, that tank is very overstocked(let alone with 2 more planned).
Also, just to be sure do you know that the figure 8 is a brackish fish?
Here is a great resource: http://home.messiah.edu/~dw1178/pufferlist.htm
- and click on the biocellatus for a profile.
Also a great website is The Puffer Forum at http://puffer.proboards2.com/index.cgi