those are dwarf puffers and are completely FW, you should really give them more cover, they love lots of plants to play in, as well a much larger tank so they can establish their own territories or get rid of all but a couple(depending on size of tank) i see at least one male in there and the rest appear to be either too young to sex or females, hopefully females because you want several females to every male if you are going to try to keep them in groups.