Stunting their growth..

How big can I let three 'feeder' goldfish get in a 28qt tub before I need to move them to something larger to keep from stunting their growth?

What are the dimensions on the tub, how is it being filtered, have you got gravel in there, what grade and how deep a gravel bed, how warm is it being kept?

Determining what kind of bioload any given aquarium can take isn't just a matter of inches and volume, species (goldfish) and metabolic rate (thus the temperature question, they produce much more waste at higher temperatures) need to be taken into account and then the specific dimensions of the aquarium, especially the surface area, are going to have an impact on oxygen exchange and the avaliable space for a biological filter bed... then the fish produce waste based on their total mass, not just their length; a goldfish that's twice as long as another is also twice as wide and twice as tall giving it about eight times the bulk- needs about eight times the O2 and produces about eight times the waste...

Quick and dirty answer, assuming a fine grade of gravel and power filtration and guessing at the tub dimensions... about an inch and a half per fish for three fish (to the base of the tail) being kept at room temperature (say 68-69 degrees) and fed appropriately. Probably stretch it to about two inches per fish before you start to have signifigant waste buildup and negative health effects if it's well established, although that's pushing it and you'll probably have to look at more frequent and more signifigant water changes.

To go along with seamus on this, it should be 10 gallons of water for every one goldfish. as he said, they produce ALOT of waste, and while the one gallon per inch of fish is usually a good rule to go by with other species, goldfish cannot handle it ^_^

Thanks guys, I had no clue about anything you said!