How To Reseal A Fish Tank – Safe & Easy Step By Step Method

    How To Reseal A Fish Tank

    A leaking aquarium is every fishkeeper’s worst nightmare. If not fixed quickly, it can endanger the lives of your fish and lead to a bigger mess to clear up. That’s why it’s important to know how to reseal a fish tank.

    Resealing a fish tank can be time-consuming, but it’s cheaper than buying a new tank. The main supplies you’ll need are aquarium silicone and a razor blade. Remove the old silicone residue with the razor blade, apply new silicone along the joints, and wait for it to cure.

    If you’d like to learn more about the right way to reseal a fish tank, our guide will talk you through everything you need to know.

    How To Reseal A Fish Tank Without Draining It

    How To Reseal A Leaking Aquarium Without Draining It

    It’s possible to reseal an aquarium without fully draining it as long as the leak is small and isn’t near the base. However, you’ll still need to drain some of the water in your tank, but only so much that the leaking area is above the water level.

    While you can use acetone and baking soda to temporarily fix a leak, it’s not a long-term solution. It’s only effective on very small leaks (less than 1 inch).

    Partially draining your tank is by far the best method for resealing a leaking aquarium without moving your fish around. It is also a much more permanent fix and will prevent you from needing to purchase a brand-new fish tank.

    We’ll be covering how to reseal an aquarium below, but this video also does a great job explaining the process:

    YouTube player

    Supplies Needed

    Before you go ahead and reseal an aquarium, there are a few supplies you’ll need first:

    Reseal Method

    Once you have all the supplies you need to repair your fish tank, it’s time to start resealing.

    Step 1:

    First things first, you’ll need to do a bit of prep work on your aquarium. Although you won’t need to completely drain the inside of the tank, you’ll still need to remove some water.

    Drain the tank until the leaking spot is above the water level. You can use an auto-siphon to do this or a jug.

    Next, clean the glass panels with an algae glass cleaner or scraper to remove any dirt or grime. It’s important to keep the glass clean so you can get a solid seal once you apply the silicone.

    Step 2:

    Use a straight razor blade or scraper to remove the old silicone from the corners inside the tank. Don’t push the razor scraper into the silicone too roughly or you could break the seam between the glass panels.

    In addition, only use steel razor blades and metal scrapers for glass aquariums. If you have an acrylic tank, make sure the glass cleaner or scraper has a plastic blade. A metal blade could scratch the surface of the aquarium.

    It’s best not to use a utility knife to remove the silicone as it could cause more damage to the seams. Make sure all the old silicone has been completely removed, otherwise, the fresh silicone will not bond well!

    Step 3:

    After you’ve removed all of the existing silicone sealant from each inside corner, clean the edges with a paper towel/cloth. This will ensure the new silicone will stick to the surface properly.

    Add a small amount of acetone to the paper towel/cloth to help remove silicone residue and debris from the seams. Then, allow the area to dry completely.

    Step 4:

    Add masking tape or something similar around the seams on the glass panels. This will help you know where to put the silicone sealant. Snip off two stripes of tape for each seam, but leave around 5 to 10 mm of space between the tape and glass.

    Step 5:

    Next, use an aquarium sealant to reseal your aquarium. Make sure the silicone is safe for aquariums as some brands contain fungicides that are harmful to aquatic life. Add the silicone to the inner edges of your aquarium as it won’t be as effective on the exterior.

    Ideally, you should apply the silicone using a caulking gun for better precision and a smoother finish. This will also help prevent air bubbles.

    Be careful when using silicone sealant bead as it releases strong fumes that can make you feel dizzy and light-headed. Make sure you only use silicone in a well-ventilated area.

    Step 6:

    Once you’ve added the silicone into the joint, use a caulking tool or your fingers to spread out the sealant. Repeat the process for all corners.

    Make sure you don’t add too much silicone to the corners as it may affect the seal. It’s best to apply a small bead of silicone and spread it out. Gradually increase the amount if necessary and wipe excess silicone away with a cloth.

    Step 7:

    When the silicone has been applied to each seam, leave the silicone sealant to dry for at least 24 hours. You can also remove the masking tape.

    In some cases, the cure time for silicone can take up to 48 hours or longer. It’s important to wait for the silicone to dry completely before you fill your tank back. Adding water too soon can weaken the seal on uncured silicone.

    Silicone sealant smells strongly like vinegar as it contains acetic acid. However, cured silicone has no odor, so this is a good way to tell when your aquarium sealant is dry.

    Step 8:

    Lastly, fill your tank back up with dechlorinated water. Make sure the previously leaking area is below the water level. Monitor your fish for a few hours to see whether the leak returns.

    Hopefully, if the leak wasn’t too severe, you’ll have successfully resealed your fish tank!

    Main Causes Of A Leaking Fish Tank

    In most cases, a leaking fish tank is caused by damage to the aquarium seal. However, there are a few other reasons why an aquarium can leak. It’s important to know which one you’re dealing with so you can choose the right method for repair.

    • Damage to the aquarium seal
    • Poor construction
    • Cracked or broken glass
    • Faults with tank equipment
    • Bad tank placement

    Damage To The Aquarium Seal

    The majority of leaks in an aquarium are due to damage to the aquarium seal. This is common in older tanks, as the silicone will eventually wear down over time. If your aquarium is more than 10 years old, it is most at risk of leaking.

    Additionally, if buying a used aquarium, make sure you check for any damage to the tank itself and the sealant. You should ask the seller how old the tank is and whether they’ve resealed it recently.

    Poor Construction

    Poor-quality or badly manufactured aquariums can leak if there is a flaw with the silicone or if the glass panes were not glued together properly during construction.

    You should always make sure you use a good-quality tank that’s strong and durable. If you don’t, it will only lead to issues in the future.

    Cracked Or Broken Glass

    A crack in your tank can cause leaks, especially if you don’t repair it quickly. A small crack can grow larger over time, so you should seal it up with silicone bead immediately.

    Faults With Tank Equipment

    Leaks in fish tanks aren’t always caused by worn-down silicone. Sometimes, they’re simply caused by your tank equipment. This could be a filter that hasn’t been closed properly or a leaking pipe from an external filter.

    Before you remove the old sealant on your tank, check that your aquarium equipment is working as intended. You may not even need to reseal your aquarium if it’s a fault with your filter!

    Bad Tank Placement

    Aquariums should be placed on a flat surface that is strong enough to hold the volume of the tank once it is filled. The surface should also be longer than your tank, otherwise, it can weaken the frame and cause leaking.

    How To Identify If A Fish Tank Is Leaking

    The first thing you’ll probably notice if your tank is leaking is water running from all the seams or a puddle by your aquarium. However, there are some other signs that can help you identify whether your tank is leaking, including:

    • Water pooling around the base of the tank
    • A crack or hole in the glass
    • Water leaking through the sealant
    • Lower water level than usual

    Smaller leaks may not be visible at first glance. A surefire way to tell whether your aquarium is leaking is to wrap paper towels around your tank. If wet spots appear on the paper towels, you’ll know that you’re dealing with a leak.

    How To Prevent A Fish Tank From Leaking In The First Place

    How to prevent a fish tank from leaking

    Fixing a leak in a fish tank can be an arduous task, so it’s a good idea to put in measures to prevent it from occurring. You’ll save yourself a lot of time and frustration in the long run!

    Fix Cracks Quickly

    A small crack in your aquarium can expand if it is not repaired quickly. This will leave you with a much bigger problem on your hands. If you notice any damage to the glass of your tank, make sure you swiftly repair it.

    Place Your Tank On A Flat Surface

    You should make sure your tank is positioned on a level surface that is sturdy and durable. Each corner of your tank should be sat securely on the surface with no overhanging edges.

    If your aquarium is not placed on a stable surface and the corners hang over, it can cause pressure on the frame. This water pressure can lead to leaks or the tank bursting.

    Be Wary Of Used Tanks

    If you’re purchasing a used tank, make sure you know how old it is. You should also check for signs of disrepair or worn-out old sealant. Aquariums over 10 years old are most prone to leaking as the silicone will be much weaker.

    Check The Condition Of The Sealant Regularly

    Over time, aquarium silicone will deteriorate and weaken, especially in older tanks. It’s a good idea to test the old sealant on a regular basis. You can do this by gently scraping it with your fingernails.

    If the silicone peels away or you can slide your fingernails under it, that’s a sign that it needs replacing.

    Use The Right Type Of Silicone

    When you’re resealing your tank, you need to use the right type of silicone, otherwise, you’ll end up with a bigger leak on your hands. Make sure you only use 100% silicone sealant that is safe for aquatic life.

    Most silicone sealants contain chemicals that are toxic to fish, so only use products that are designed for aquariums. Aqueon Aquarium Silicone Sealant is a great choice.

    In addition, when removing the old sealant, don’t use a utility knife as it could cause more damage. A razor blade is best for glass aquariums, whereas a plastic scraper is better for acrylic tanks.

    How Much Does It Cost To Reseal A Fish Tank?

    How much does it cost to reseal a fish tank

    Resealing a fish tank yourself without professional help should only cost $20 at most. Most of the supplies you need for resealing an aquarium like masking tape are cheap or are likely already lying around your house. 

    The main expense of resealing a fish tank is a caulking gun, but this is an entirely optional tool. You can reseal an aquarium without one just fine. However, using this tool will make applying the silicone easier and provide a smoother finish.

    Is It Worth It To Reseal A Fish Tank?

    Resealing an aquarium is usually worth it provided the leak is not severe. It’s much cheaper to reseal an aquarium than purchase a new one, especially if the tank is large.

    That being said, there are also a few cons to resealing a fish tank. It’s important to be aware of these so you can decide whether it’s the right step forward.

    Pros Of Resealing A Fish Tank

    Below are some of the pros of resealing aquariums.

    • It’s Usually Cheaper Than Buying A New Tank

    In most cases, fixing a fish tank is a lot cheaper than buying a new aquarium as it usually costs no more than $20 for the whole process.

    A high-quality or very large aquarium can be very expensive. Replacing one could set you back hundreds of dollars.

    • You Don’t Need To Move Your Fish

    Draining your entire tank and moving your fish to another aquarium can be fiddly and time-consuming. However, it’s possible to repair an aquarium without doing either of these things if the leak isn’t too big.

    This saves you a lot of hassle and prevents your fish from becoming stressed from moving to a new enclosure.

    Cons of Resealing a Fish Tank

    Although fixing a leaking aquarium with silicone can be a good option if the leak is small, there are a few scenarios when it might not be the best choice.

    • It May Not Fix Large Leaks

    Big leaks in a fish tank may not be solved by simply resealing it with silicone. This can occur if the leak originated from a crack in the glass rather than a hole in the seal.

    In this case, you’d need to replace the glass panes or purchase a new tank altogether.

    • It Can Cause Bigger Problems If Not Done Correctly

    Although resealing an aquarium can be more cost-effective than purchasing a new aquarium, it can cause bigger issues if you don’t do it right.

    For instance, if you don’t remove all of the old silicone inside the tank, the new sealant will not bond. If the new silicone doesn’t seal properly, it will not repair the original leak and may even result in a larger leak.

    Alternatively, if you don’t allow the new silicone to dry and cure fully, it will wash away once you fill the tank back up with water. This will cause additional leaking and require you to repeat the process all over again to save your aquarium.

    • It May Not Be Worth It For Small Tanks

    A large leaking aquarium can be pricey to replace, but smaller tanks are usually much cheaper. It may not be worth resealing a small aquarium if it didn’t cost much more than the supplies you’d need to fix it.


    Resealing a fish tank can be a time-consuming and fiddly process, but it’s the best course of action for fixing a leaking aquarium without purchasing a new setup.

    However, you need to make sure you have all the right supplies and follow the correct method. It’s vital that you use an aquarium-safe silicone and allow it enough time to cure. Failing to do so could harm your fish and result in an even bigger leak.

    Sometimes, it may be better to replace your tank, such as if the leak is caused by a deep crack in the aquarium glass. But, in most cases, it’s well worth attempting to reseal your aquarium first to see if you can repair the leak.

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