I'd say a 180 is preferable, piranhas are active swimmers and need ligit space, maybe that's why they bash into the dw? Their only at about half size now, imagine them almost 2x that size.
15 gallons per adult caribe is not enough imo and by quality standards yes it is slightly* overstocked, nothing major as of now but remember their growing, my reds are nearly the same size and my shoal of 5 creates a fairly large bio load, couldn't imagine 8.
It's nothing personal I just don't want new members coming here and thinking its okay to cram 8+ piranhas in a 18" deep tank.
125 gallons is not that big, I wish I would have bought a 180 or 220 for my shoal. Bigger the better especially with Piranha!
Can't believe no one has bought them yet, that's crazy. Glws
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http://www.monsterfishkeepers.com/forums/showthread.php?504763-Cheap-plants-less-nitrate!-POTHOS
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