tetraodon suvattii puffer. Those things are *MEAN*. I used to have one in a 15g (a tad on the smaller side for a full grown one). As soon as they see something move in a tank they go explore. And by explore I mean bite a chunk out of it. They can tear up huge goldfishes in seconds, bite by bite. Their mouths aren't huge, but their teeth are sharp and they will bite huge chunks of flesh in every bite.
They get large-ish, but because they don't move much they don't need too much space, just good quality water.
They get large-ish, but because they don't move much they don't need too much space, just good quality water.
