Red bellied piranha = BORING, they are scardey cats and are not the blood thirsty killers they are made out to be.
A black rhombus is a littler cooler but solitary there not exactly the fastest seeming thing on the planet then you toss food in there for IT (solitary fish will eat his buddies so wil the red bellies, in time just not asw quickly...)
if and only IF you can find a gold or purple (Serrasalmus spilopleura...there the same fish) you'll get the devil incarnate w/fins.
again hes not tolerant of tank mates especially his own kind.....and hes not very tolerant of your hand either I reccomend a mesh chain glove for tank cleaning you can have my old one if I can dig it up, it may sound dorky but I can still count to ten(with the one I had I'm shocked...honestly)
They are illegal to keep in the state of washington and honestly not worth the risk IMO. I had a few tank of piranahs, alligators(camin and american) and an alligator snapping turtle. And would not reccomend ANY to a fellow hobbyist (unless they enjoy the smell of dead carcass in there house, meat eaters + water = BAD JUJU, don't feed your piranahas mice for your own sake)
There are several more exciting (and aggressive.... AND dangerous.....) killers you can legally have in washington state.
one of which is an african tiger fish after he gets to be about 12" you'll want a full chain mail or leather sleeve for tank matinence, and they get BIG. There dumb for people to get, but legal.
and What I would reccomend you get is a LARGE school of exodon tetras. attitude of a tiger fish half the size of a piranha and NOT shy, your arms and fingers may even stay intact with these guys. They display parasitic behavior like piranhas being fin and scale eaters. A larger school of these will dismantle almost any fish you throw in the tank with them very quickly, and feeding response is instant. Food hits water fish hit food, not necessarily the same result will yeild with any piranha (except the gold/purple...he's evil).
and best of all there LEGAL in washington too.
