All piranhas are super boring, maybe somebody should take my advice and save their money for something else. I have owned 2 manny's,1 black diamond rhom,1 black rhom,1 geryi, 1 sanchezi,1 compressus and redbellies. I kept these fish for long periods of time and my black diamond rhom I had for over 4 years. So can't say I bought them on a whim and sold them the next day. I am just helping you out and trying to avoid you the disappointment to own either one. If you were going to buy anything Piranha....Then spend the money for a 15 to 16" black rhom. They have totally different personalities then the small ones. When you buy them at this size don't expect them to live for 15 years as they are already "OLD" but the personality will make up for there short life span. Probably live 3 to 5 years. Take it from someone that has done lots of research on the subject of piranha's.
Im going to disagree with you on the geryi, my lfs has a giant one and it attacks the glass when ever someone comes near.
I would get the manuelli
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Never once was I bit by any of my piranha's that I owned.