if you want black piranhas i would go to aquascapeonline or sharkaquarium
sharkaquarium has some 4 inch rhoms right now for 59.99 but i never bought from sharkaquarium
i would like your dimond but i dont have a big enough fish tank i have a 95 gal and im going to buy a pack of caribes 1-3 inches and in my 75 gal im goin to put a black piranha
Have you ever kept any piranha? I would try out one or the other before jumping fully into it. Personally I wasn't too happy with the idea of my fish tank comming with piranha but there nothing like I expected.
i hope you do some research on growth rates. It's painfully slow. I think a 1-4 inch baby black rhom would have a hard time finding it's food in a 75 gallon.