A constant diet of rosies while in a 20 gal tall is equivalent to you eating twinkies for a year while locked in a closet
I'm not suprised your P hasnt grown much at all. You need to start feeding it white-fleshed frozen fish and shrimp if hes large enough to take it. Also, you need to put him in a tank with a larger footprint.
12 inches wide (on the 29 gallon) is a bit on the narrow side in my opinion but it should last your piranha a couple of years. Definately start giving your fish healthier foods and going to the rosies only as a treat however
Well, everyone has already stated it... but -- only feed your piranha rosies about once a month or so. The same with beefheart. These should be recognized as treats! Even though some have given you some suggestions as far as tanks go.. For a single red -- he would be extremely happy in a 55 gallon.. IMO 55 gallons are really not that expensive either. If you can not afford a new one (and I would understand) occassionally look in your newspaper or even on ebay ..
Good Luck, but you definitly need to change his diet and get him a bigger home!
well the suggestion of a larger tank is always the cure to happy p's.
also the diet that you are using needs more variety.
its going to be hard to make the transition from live food to frozen, but starve him for a while. since you only have one, you wont need to worry about cannibalization.
after he gets use to frozen i would suggest picking up a few more rbps and a larger tank. 55+ would be ideal.
this would promote their natural predator skills, and overall look better imo.
lastly, you should really do both you and your pet a favor and buy a powerhead if you dont have one already. and waterchanges water changes waterchanges...