How to Repair Aquariums With Silicone Sealant

Jun 14th 2022

Fish are beloved pets that are easy to take care of. Even so, there are a few things you need to prepare for before welcoming a new pet into your home. If your aquarium is in need of repairs, silicone sealant can help! Here’s how to reapply silicone sealant to a chipped and/or leaky aquarium.

Silicone Sealant for Aquariums

You may associate silicone sealants with home improvement, kitchens, and bathrooms. But, did you know that you can also make aquarium repairs with silicone caulk? Silicone sealant can be used for basic repairs, adding on decorations, and sealing aquarium glass. For the most part, caulk is perfectly safe for fish tanks as long as it’s 100% silicone. Hybrid forms of caulk may contain additive chemicals that could harm your fish.

Selecting Aquarium-Safe Silicone

As mentioned previously, caulks made out of 100% silicone are harmless for aquariums. Some brands take the initiative to add an “aquarium-safe” label to assure fish owners of their safety. The primary reason silicone sealants work so well for aquariums is because of their water-resistance. Silicone sealant is flexible, durable, and capable of withstanding environmental changes. This makes it ideal for waterproofing glass fish tanks and repairing leaky aquariums.

Repairing Your Fish Tank

Whether you’re just starting out or repairing an old glass fish tank, knowing how to make basic repairs using silicone sealant can greatly improve your aquarium. Applying aquarium-safe silicone sealant can also prevent previous toxins from leaking into the fish tank. It can also be helpful if you’re repairing a secondhand aquarium that may have been previously used by reptiles or cleaned with toxic chemicals.

Before waterproofing your aquarium, it’s important to inspect the tank for any noticeable cracks or chips along the glass. When looking for cracks, it’s good to make repairs based on its thickness and proximity to the glass. Generally speaking, small, thin cracks can be left alone. However, if you notice a crack that’s thicker than the glass itself, that’s cause for concern.

Similar rules apply to the frame of the fish tank. Observe the frame for any previous adhesives or forming cracks. If the frame is loose, remove it for future repairs/replacement. If you notice old silicone sealant on your aquarium, focus on removing adhesive on the inside of the tank. Only remove silicone sealant between the glass if you notice loose pieces of caulk.


Here are the tools and supplies you’ll need before applying silicone sealant to your aquarium:

  • 100% silicone sealant (aquarium-safe)
  • Caulking gun
  • Masking tape
  • Scraper
  • 5-in-1 painter’s tool
  • Single edge razor blades
  • Box cutter
  • Distilled white vinegar
  • Paper towels
  • Spray bottle
  • Clean rags

Preparing Your Aquarium

Before applying new silicone sealant to your aquarium, make sure to clean it thoroughly with water and set it down on a soft, protective surface. Clear your work area of any dirt, rocks, or debris. Carefully set the tank on its side to avoid the need to dump any water out, as this can contribute to further cracks.

Once you’ve cleaned the tank with water, place it in an upright position and add a little distilled white vinegar to a clean rag. The acidity of distilled white vinegar will easily clear away dirt, grime, and hard water stains from your aquarium without harming your fish. Repeat this process until the tank is clean before rinsing out the rag with clean water.

Removing Old Silicone

Use your spray bottle to fill up half of it with distilled white vinegar and the other half with water. From there, take your 5-in-1 painter’s tool to start removing the old silicone. Use the box cutter to cut off any loose pieces of silicone and remove them from the tank. Make sure to avoid using too much force with sharp tools to prevent the glass from chipping.

If the frame has been removed, use your painter’s tool to remove the excess silicone sealant that held it in place. From there, take the spray bottle filled with distilled white vinegar and your single-edge razor blade to clear away remaining pieces of silicone sealant. Once you’ve completely removed the silicone, use a clean rag dampened with distilled white vinegar to clean the tank. Proceed to use another clean rag and water to clean up the vinegar.

Resealing Your Fish Tank

Place your aquarium at an accessible and comfortable position. Proceed to use the masking tape to mark the areas you’d like to caulk. Prepare the caulking gun with the silicone sealant cartridge and cut the tip at a slight angle. Test out the adhesive on some newspaper if you want to practice the application process.

Start applying a bead of silicone on the inside seams of the tank. Proceed to apply beads along the corners of the aquarium, starting from the bottom up. After finishing the corners, finalize the application process by adding silicone to the top of the aquarium. Allow the silicone sealant to cure for a few hours before carefully removing it away from the seal.

Repairing Your Frame

If you had to remove your aquarium’s frame to perform repairs, apply a bead of silicone to the top of the glass and press the frame down to secure it to the tank. If the frame was reattached or wasn’t removed to begin with, apply a bead to the underside of the tank’s frame and smooth it out.

If you still need to seal the bottom frame, wait for the aquarium’s silicone sealant to fully cure for at least 24 hours. From there, reattach the bottom frame by applying a bead of silicone to the edges of the bottom glass. Secure the frame with pieces of masking tape and let the entire aquarium cure for 5-7 days.

Finishing Up

Once you feel confident that the tank has cured completely, bring the aquarium outside to test it out. Start out small by only filling it about ¼ of the way with water. Proceed to fill the tank little by little every 30 minutes until it has reached the top. If you don’t notice any leaking water or areas where more caulking is needed, rinse the tank of any residual vinegar and proceed to prepare it for fish!

Silicone Depot offers aquarium-safe silicone products for any necessary repairs or reapplications. We always offer high-quality silicone sealants and caulks at wholesale prices. Check out our selection of silicone products today!