How to Move to a Larger Aquarium

Answer: Upgrading to a larger tank is a great idea, and something you won't regret. Bigger tanks are easier to maintain, not to mention the fact that you can keep more fish. The fish as well as the gravel can be transferred. What about the water? I'd leave most of it behind. The water itself is not the source of bacterial colonies. The beneficial bacteria colonize the filter media, the gravel bed, and other hard surfaces of the tank, such as rocks and decorations.

Here is how to successfully transfer from an established smaller tank to a new larger tank.

Prepare the Old Tank
Lightly vacuum the gravel in the old tank to remove any large particles. Test and record the pH and water temperature so you can match them to the new tank.

Set up the New Tank
Because you have a much larger tank, I assume you'll have a new filter and heater, as the old ones will not be sufficient to filter and heat a much larger tank. Set up the tank and fill it three fourths full of water. That is enough water to set up and start the new filter and heater, and leaves room for gravel and decorations. Let it run for twenty-four hours.

If you plan to use the old filter in the new tank, leave it running on the small tank. Run an air stone in the new tank if you have one. That will help drive off any chloramines that may be in your water supply.

What if you planned to use the old heater in the new tank? Reconsider your decision. Even if it isn't too small, the new tank should be run for a while with a heater to assure that the temperature is stable. Furthermore, it's wise to have more than one heater on hand, as you never know when a heater may fail.

Test the Water
After twenty-four hours, test the pH and temperature in the new tank and compare to the old tank. Don't proceed with the transfer if there is a difference between the two tanks of more than two tenths in pH, or a couple of degrees in water temp.

Move the Gravel
Using a clean cup transfer the gravel from the old tank to the new tank (I like disposable plastic cups that I can throw away when I'm done). Move any rocks and decorations next. If you planned to use the old filter in the new tank, move it at this time and make sure it's running before moving the fish.

Move the Fish
If the pH and water temp match exactly, you can transfer the fish without having to net and bag them. If there is a difference in temperature and pH, you'll have to bag the fish and acclimate them the same way you would a fish you bring home from a pet shop.

For a direct transfer use a disposable plastic cup and a net. Hold the cup underwater and use the net to drive the fish into the cup. Lay the net over the top so the fish can't jump out, then place the cup in the new tank and let the fish swim out.

Although the cup and net technique might not work for all fish, it is a less traumatic way to move many of your fish. For those that cannot be moved using the cup, net them and place them in a sturdy baggie filled with water from the tank.

Move the Filter
What a minute! Didn't I advise buying a new filter for the new tank? Yes I did. However, the filter from the old tank has beneficial bacterial colonies in the filter media. By running both the old and new filter for a few weeks, you'll introduce lots of beneficial bacteria in the new tank. The extra filtration will also be helpful as the new tank becomes established.

After the Move
You'll still go through a startup cycle, however transferring the gravel will speed up the process. Treat the new tank as if you had just started out, which means you should test the water for ammonia and nitrites until they are zero.