Figure eight puffers

Question
This is going to be my first time keeping a figure eight puffer and I have already been doing some research online. I have a ten gallon tank that has already been cycled and is ready to go, I already have a pleco and some snails. I would like to know whether or not figure eights are brackish water or freshwater? I would also like to how many I could actually keep in my tank?  

Answer
Hi Eric,
There has been lots of debate about whether or not figure-eights should live in brackish or freshwater. I believe that they can go both ways equally well. One of the most important things to make sure of before you bring a puffer home is that their aquarium is fully cycled... Figure eights cannot tolerant ammonia or nitrites. You already have that taken care of though so good for you!

I hear repeated stories of success with keeping Figure-eight puffers in freshwater aquariums perfectly well. They originate from freshwater rivers in Southeast Asia... Despite this, it is still often recommended that you keep their aquarium lightly brackish. It might be possible that the addition of salt acts as a discouragement to common fish illnesses. But if you maintain a proper diet and do not allow the water quality to deteriorate since poor water quality is the number one reason fish become sick... Illnesses should not be a problem for you.

Figure-eight puffers do best as loners in your aquarium. More than one may induce fights like territorial battles. And especially since your aquarium is small keeping more than one may indeed turn into a bad situation. While they aren't "killers" they will constantly peck and bite at one another and could quite possibly make one or more individuals miserable.

Continued research is always your best bet in finding out as much as possible about these interesting little creatures!

I hope this helps!
Karen~