How to safely upgrade a fish tank

a woman and two children looking at a fish tank.

Getting ready to upgrade a fish tank to something bigger and better? How do you make sure they survive the transition and get comfortable in their new home? Be sure to follow the next few steps to make the process painless!

You MUST match pH and temperature between systems.

Your tank pH and temperature is critical to match before moving your fish into their new home. If these two parameters are significantly off from each other, your fish may become too stressed out and die. Other parameters, such as your nitrogen cycle, should always be lower when starting a new system.

Always run your old filters with your new for 4-6 weeks.

In doing so, this will prevent New Tank Syndrome, where your biological filtration hasn’t been established. If you are running a heavy fish load during the tank upgrade, you risk shooting your ammonia up to dangerous levels. By running your old filtration with the new, it will give you some buffer to allow the new filter media to become seeded with good bacteria. Test your water DAILY to make sure all your parameters are staying within range.

You can add in up to 50% of your old tank water to the new tank.

You can add more “old” water, if you like, but no more than 50% new. This will make it a little easier to match your pH and temperature.

If your water chemistry parameters match, you do not need to acclimate your fish to the new tank.

If you just cannot get your pH and temperatures to match, or your old tank is very off range, such as with Old Tank Syndrome, be sure to properly acclimate your fish very slowly over a long period of time in order to them to survive the move.

If you are having aggression issues, be sure to add the aggressive fish LAST.

By adding the more aggressive fish last, you will allow the others to find a good hiding spot and not be ousted by grumpy roommates. If you are having aggression issues, try to figure out what is the most limiting factor and try to correct it. For many aggression issues, more space and a larger tank may be the solution!

Buying used equipment? Be sure to clean it first!

Never buy used equipment where all the fish “mysteriously” died. Never buy equipment that is not “fish-safe.” Use an appropriate cleaning agent and make sure everything can dry fully.

Whenever you move your fish, it will be a stressful process for them. Take your time setting your system up properly and safely move your fish. Keep the old tank for a few weeks just in case some of the fish don’t handle the move and need to be quarantined. It is always a good idea to have a hospital tank on hand, just in case.

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2 thoughts on “How to safely upgrade a fish tank”

  1. I want to upgrade my beta from a 3 gallon to a 5 gallon. Can I use the existing water from the 3 gallon in the new tank and then supplement it with spring water. It says not to use more than 50% new water. I have been having a problem with ammonia at . 25. Will this be a problem when transferring the old water to the new tank

    1. a woman in a lab coat smiling for the camera.
      Dr. Jessie Sanders

      The new water will dilute out the ammonia in the current tank, so it is okay to use. Congrats to your fish on their new tank!

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