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Upgrading to a Larger Aquarium

Moving Your Fish to a Healthier and Larger Home

(The First Tank Guide)

When setting up a new tank, I recommend setting up the tank and letting it run for at least a day to check that the tank does not leak, and that the equipment all works, and to get the temperature stabilized, then introducing the first fish to try to get the cycle going. However, when moving to a larger tank, you are better off setting up the new tank using as much equipment and water from the old tank as possible, and immediately introducing the old fish to their new tank. However, I do not recommend getting any new fish until you are sure the tank is stable.

Follow these steps when moving your fish to your new, larger aquarium:

  1. Rinse all the equipment for the new fish tank, including the gravel, filter media, any decorations, and, of course, the fish tank itself in cool, running tap water. This will remove any debris from manufacture, packaging, storage, or shipping and should reduce the cloudiness you'll experience with this new fish tank at first.
  2. Place the new aquarium where you want it, set up the equipment and get everything ready to go for the new aquarium.
  3. Drain the old tank by siphoning the water into buckets.
  4. Net the fish and carefully place them in one of these buckets of water from the old fish tank. Make sure that the buckets you are using have no residue from soaps or detergents, to prevent the toxicity of these chemicals from harming your fish.
  5. Scoop the gravel out of the old tank and place it in the new tank, then add the water from your buckets to the new tank, leaving the bucket with the fish in it for later. If this is enough water to get the filter started, do so. Also Place the filter from the old tank on the new tank at this time and start it (after a few weeks, once the new filter is established, you can remove the old filter if necessary). You'll want this old filter on the new tank to help keep the biological filter stable during the transition. You should also take this opportunity to set up your decorations in the new tank. Remember, even the decorations in your tank will contain beneficial bacteria for your biological filter, so feel free to use those as well.
  6. If this is enough water for the fish to swim freely, gently net the fish out of the bucket and place them in the new tank. If this is not enough water for the fish to be able to swim freely, you will want to add fresh dechlorinated tap water to the tank until you have enough water for the fish to be able to swim around. Once you have introduced the fish to the new tank, add the water that they were in to the new tank.
  7. Top off the tank with fresh dechlorinated tap water. Do your best to keep the water you are adding to the tank close to the temperature of the water that is in the tank. This helps to minimize the stress to the fish and the biological filter due to the move. Floating or standing aquarium thermometers are available at most pet stores, and are fairly inexpensive. Also, the average human hand can differentiate between temperatures within about 1/2° Fahrenheit (1/4° Celsius), so keeping the temperature close should not be much of a problem. If your water heater runs out of hot water, feel free to let the tank sit while more water is heated.
  8. After you have the new tank filled, let it sit for at least half an hour, then plug in the aquarium heater and begin the process of setting the heater to the correct temperature.
  9. Feed sparingly and do not introduce any new fish for at least 4 weeks to make sure the tank stabilizes well. This will give the bacteria for the biological filter time to populate your new filters and will allow the fish a chance to get used to the new tank. Some time around three or four weeks in you can remove the old filter from the new fish tank. This should have given the new filter time to start growing a colony of the beneficial bacteria that will process the fish's waste. watch the tank closely for at least three weeks after removing the old filter for any signs of ammonia stress, as a few extra water changes may be necessary as the tank finishes stabilizing.

Once your new tank is set up, remember to watch the fish as though you were cycling the tank again. Following the instructions provided above, you are not likely to have to go through much of this process again, however, it is a possibility. Of course, your new tank will still require regular water changes and routine maintenance of the filters, and the same loving care your fish received in their old home.

Setting up a new aquarium can be an exciting adventure and a source of fun for the whole family - even if you have had an aquarium before.




"Great Web site, by the way. I like your philosophy and advice."
July 22, 2007
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"Kudos! You have an excellent, informative and accessible site. Well done!"
January 9, 2004
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