How Long?

[GobyMaster]

How long do you think that I could keep some goldies in a 30 gallon tank before I'd have to move them to the pond in my backyard?

They'd probably be commons.

 

[Colin_T]

It depends on how many fish and how big they are to start with. Also on how often you feed them and do water changes and on how much filtration you have.
You could have 10 small (2inch) common goldfish in there indefinitely but they would need regular water changes and won't get as big as they could out in a pond.
You could have a couple of 6inch fish in there but they would be a bit confined and you would have to keep an eye on water quality.

 

[GobyMaster]

It'd be about 30 gallons of water, and there would be maybe 4 or 5 goldies in it, and then 2 tadpoles

 

[Colin_T]

how big are the goldfish going to be?
how often do you plan on feeding them?
how often do you plan on doing water changes & gravel cleans, and how much water will you change?
what sort of filtration is on the tank?