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How to Fix a Leaking Aquarium

Updated on December 19, 2012

Fixing an Aquarium Leak -

Waking suddenly with the cold sweats, the aquarist panics and quickly sprints towards her fish tank. Realizing that the floor is dry and her fish safe and sound, it suddenly became clear that the leaking aquarium was all just a nightmare.

Okay, so our fictitious aquarist may have gotten lucky, but the cold hard truth is that many of us find ourselves living out the ever so real nightmare of a leaky aquarium. So, if you're left stuck tying to figure out what to do, look no further. This guide is designed to show you all the steps necessary on how to repair a leaking aquarium!


Tools for the Job -

  • Aquarium Safe Silicone
  • 91% Isopropyl Alcohol (Rubbing Alcohol)
  • Latex Gloves
  • Razor Blades
  • Vacuum
  • Masking tape

** Be sure to choose an aquarium safe silicone for your project. Many silicone types available for purchase have added fungicides and are toxic to aquatic life. Purchase silicone from either a reliable pet shop or look for DAP 100% Silicone for Aquarium use at Lowes or Home Depot. If neither can be located, GE #1 for Windows and Doors may also be used.


How to Repair a Leaking Aquarium -

No matter how small the leak or its location, the aquarium must be empty and dry so that the repair can be made! With that said. . .

Vacuuming the aquarium frequently helps remove all silicone scraps.
Vacuuming the aquarium frequently helps remove all silicone scraps.
Cleaned with old silicone removed.
Cleaned with old silicone removed.
Guide tape for new seams. Bottom trim of tank was removed for illustrative purposes.
Guide tape for new seams. Bottom trim of tank was removed for illustrative purposes.
New silicone seams in place with guide tape removed.
New silicone seams in place with guide tape removed.
Finished aquarium drying.
Finished aquarium drying.
  • Step 1: Check the condition of the glass all the way around the aquarium. If all panes are in good shape (not cracked or chipped), the aquarium leak was most likely due to silicone failure.
  • Step 2: Using caution and fresh razor blades, remove all silicone from the inside of the tank. It is extremely important to remove all the existing silicone, as the new silicone will not bond properly if any chunks or residue is left behind. Be patient and remove all silicone! Vacuum up the chunks as needed.
  • Step 3: Clean the tank inside and out with a towel and isopropyl alcohol. With the tank cleaned, you will now be able to see if it is ready for new silicone. If no bits or scraps of old silicone remain, move onto the next step. If there is silicone to be had, make sure it is removed!
  • Step 4: Use tape to create guides for where the new silicone will be laid. This step is optional, but will create much straighter and cleaner looking silicone lines for the finished aquarium. On the five gallon aquarium shown, I allowed for 1/4 inch between the end of the glass pane and the guide tape.
  • Step 5: Clean the seams that you plan to silicone one last time with a towel and rubbing alcohol. This will remove any remaining oils, dust or grim and will ensure the best possible bonding surface for the new silicone.
  • Step 6: Working quickly and holding the silicone tube at a 45 degree angle, apply a thick and consistent bead of silicone to all glass seams. Be sure to put a bit more silicone in the bottom corners where the panes meet.
  • Step 7: Within 5-10 minutes of applying the silicone, smooth out the seams with your finger for a professional finish. This is best achieved by wearing a glove and constantly dipping your finger in the rubbing alcohol to prevent the silicone from sticking. Apply gentle pressure, ensuring that there is no air bubbles in the newly applied silicone.
  • Step 8: After smoothing out the seams, but still while the silicone is tacky, remove the guide tape. Any silicone outside the guide lines can be cleaned up once fully dry.
  • Step 9: Allow the tank to fully dry for at least 3-4 days.
  • Step 10: Test the new silicone by filling up the tank in a place where you don't mind getting wet. If the tank holds water for a couple of days without issue, you're good to go!


While the project is not extremely difficult, it is very tedious. Just make sure that all the old silicone is removed! Thanks for reading this article on how to fix a leaky aquarium. Please leave any comments or questions you may have.


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