Switching goldfish to a new, bigger tank.?

by  |  earlier

0 LIKES UnLike

My goldfish that I rescued last year has been living in a 5 gallon tank, and has obviously outgrown it. I purchased a used 25 gallon tank and want to know the proper way to set it up and transfer him over, so I don't cause him to go into shock and die.

Do I need to cycle and set up the new tank and get an ecosystem going before he goes in? Also, is it better to have an undergravel filter, or an overhead one? Or can I combine both?

I'd also like to get him a friend, as I believe a 25 gallon tank should be big enough for both. He should get along fine with another goldfish, right?

Thank you!




  1. Best option.

    Move the filter that's in the small tank into the bigger tank along with the goldfish. That will jumpstart the cycle in the new tank. You are bringing most of the cycle bacteria with the filter.

    Yes a 25g tank should be able to support 2 fancy goldfish, as long as you have good filtering and plenty of water changes. Goldfish are generally social fish and like to live with other goldfish.


  2. Set up your new new tank and let it stand for a day or so to allow the water temp to become the same as the old tank before moving your fish (room temp for cold water fish). An under-gravel filter should be fine,the waste products will feed the plants.

    Goldfish usually live peacefully with other similar fish.

  3. Yes that will be fine for two fancy goldfish. If yours are not fancy and are commons or comets just keep in mind you will need to upgrade in the future.

    I wouldn't go with the under gravel filter I would do the hang on back. I prefer a marineland penguin 200b or an emperor 280bd with a bio wheel. These filters are rated for 50g tanks as you will need double the filtration for goldfish

  4. if your goldfish is a fancy (2 tailed one) it will be fine in the 25 gallon, with another fancy goldie. if it is a common or comet goldie he will eventually need a bigger tank again, for 2 i would say 75 gallon to allow them to grow to their true potential. dont go for the under gravel filter as all teh p**p/uneaten food will be held under their, a canister filter would be much better,and get one that is over rated for your tank tpo keep up with the goldie p**p,they ar every messy fish. as for cycling, if you swap all of the gravel from your current tank into the new one, remember to add dechlorinator to your tap water so as not to kill off the bacteria, and add the filter you already have aswell as a new one and run them both on the tank for a month the old filter will seed the new one and the cycle wont take long at all if it does even cycle again. good luck with your fishy.

Question Stats

Latest activity: earlier.
This question has 4 answers.


Share your knowledge and help people by answering questions.
Unanswered Questions