2 comets in a 20 gallon?

[bubbleflare]

My english teacher was convinced by me to rescue to 2 comets from a 1 gallon tank that recieved a water change every week. He did some good preparing by reading on proper care and stuff, unforunately the website that he read from stated goldfish needs 10 gallons each so he bought a 20 gallon instead of something bigger.
He had them for 5 month now, they have shown rapid growth and are now 3 inches (orginally only 1 inch). I fear the tank is getting small but he cannot upgrade to a desired 75 gallon until he moves into a house which is 2-3 years from now.

Will the comets get stunted in a 20 gallon?
Other then space, these comets gets water changes religiously and a quality pellet diet.

[LittlePuff]

I would keep them in in a minimum of 40gal. Stunting is likely, but if you can't convince him to get a larger tank, large, very frequent water changes are all that will help. 

[Cholly]

It's not actually the size of the container that stunts, it's the concentration of hormones and pollutants. If the water is clean enough, they'll still grow. It's just that the concentration builds up so much quicker in a smaller container.

[LittlePuff]

They will grow to up to 12", a 20gal tank IMO is too small.

[Cholly]

They're aware Puff, they want to upgrade, but have limited space themselves apparently. More frequent large water changes will work for short term, but nothing will help like an increase in tank size.

[LittlePuff]

Agreed.

[RinsMom]

Considering that a 29 really doesn't have THAT much of a larger footprint, would that be a more suitable size?

If the teacher is short on funding, suggest Craigslist or freecycle... it is amazing the prices on larger tanks that you see sometimes.

Common goldfish can grow VERY fast in optimal conditions... my daughter got a 1-1 1/2" feeder goldfish to eat the snails in her 29 gallon... in 5 months, it grew to about 5".  We put it in my water garden this spring, and it is now probably 7-8" (maybe larger) .... and it has been just over a year since she got the fish!