I think a piraya would be really sweet to own...I might not place it with my reds but I wouldn't mind having a shoal of like 6 by themselves or mixed in a large tank with some caribe. The growth potential and the ability to shoal makes that decision lean towards getting the piraya at least for me anyway.
OK you guys made my mind up.. Im gonna check out the Piraya later this evening to make up the final decision. If I do trade my Rhom, I will most def go 12"+ bigger or divide the 30 gal and get 2 different baby Serras.
Also, a question for you Piraya owners. Aren't they more sensetive with water perimeters than Caribas or even red???