possible new tank

[tttnjfttt]

I may be getting a 40 gal tank soon, but the one I am looking at (used) doesn't come with a filter or heater. Until I can afford to get a new filter, would it work to use my 20 gal filter if I don't add more fish?

 

[freddyk]

Absolutely - same fish, same bioload - no problems.

 

[FrankSlapperinni]

The only problem is that the water turnover would be cut in half. Ie, if in the 20 gallon it was able to run the tank's complete volume through it 10 times and hour (200gph), I would only run it through 5 times an hour in your new tank. But since the fish came from a twenty gallon the 40 would be considered understocked, so it should be all right.