Ok...so the school of these was sold as "Silver Dollars"...but it's got a heck of a different pattern than most I've seen....it's fins are red, and it has a red dot behind it's operculum...and it has spots...

I think I've got it down to the genus...but the species still elludes me...any help?

Could be a pacu/silver dollar cross.

I think they are young markings that will fade and disappear with age. Looks like a Metynnis argenteus from the shape. There is the spotted Metynnis but the head shape doesn't look right for that.