IMHO it is not a red-eye (Carinotetraodon), but one of the target group. It could be a brown puffer (Tetraodon turgidus), or could be a Fang's (T. cochinchinensis) -but the spot is not red at all, or one of the others. The "group" is hard to ID. They range from 3 to over 6", are generally nasty-tempered toward any tankmates, not very active, like heavily planted FW tanks with a selction of overhangs/plant clumps where they can rest and watch.