Resealing Your Glass Tank

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Reef enthusiast
How to Completely Reseal Your Glass Tank

by Thaiboxer


What you will need/want to have before beginning:

1. Bottle or tube of 100% silicone, your able to pick these up either at your local HD, LFS, or your nearest Home Improvement Center. Make sure your silicone doesn’t have any antifungicides or other additives – they can kill your fish! If you’re doing a large tank, get at least two tubes – you can always return the extra. Better to have too much on hand than not enough – I used just over two tubes for a 125 gallon tank.

Note: I got tubes of 100% silicone marked “aquarium safe†by DAP for $2.97 each.

2. Razor Blades (caution very sharp). I also recommend getting one of those metal holders that grips the razor blade for ease of use.

3. Bottle of Rubbing Alchohol, a shot glass, and cotton swabs or paper towels.

4. Mineral Spirits (This is to clean your hands and tools later!)

5. Pliers (These are handy to get that last little big of silicone out of the tube.)

Note: When you get to step 3 below, it will be a lot easier if you have a
friend to help!

What to do:

1. If the tank isn’t already empty and dry, empty it and let it dry! Use your razor blade to remove all of the old silicone from the glass. Try to get as much as you can out from in between the pieces of glass as well. Use a vacuum to periodically suck up the pieces of silicone you’ve carved away from the glass so you can see what’s still attached.

2. When you think you’ve removed all the silicone and the tank is clean, dampen a cotton swab or paper towel with rubbing alcohol and run it along the corners with your finger. You should be able to “feel†the sticky spots on the glass where a little bit of silicone remains. Go around the tank 3-4 times cleaning off any remaining silicone with alcohol and a razor blade, letting it dry after each cleaning. When you are satisfied that all of the old silicone is gone, let the tank dry completely and go on to the next step.

3. You are now ready to apply the fresh coat of silicone. Before you start, fill a small glass (shot glasses work great) about halfway with rubbing alcohol. Silicone dries quickly so you’ll need to be very efficient, especially if you’re working on a large tank. Set your rubbing alcohol in the tank (I worked with the tank standing up), and cut the nozzle on your silicone tube.

Note: For my second coat, I had a buddy apply the silicone while I followed with rubbing alcohol and my finger. It went a LOT smoother
using this method, I highly recommend it!

4. Working alone: Squeeze your silicone bead along an entire edge of the tank, and don’t be stingy! If you’re working alone: when you’ve finished applying the silicone to an edge, dip your finger in the rubbing alcohol and smooth the entire edge making sure there are no air bubbles. Wipe your hands (mostly) clean with a paper towel and move on to the next edge, covering them all in the same manner.

4a. With a friend: Have your friend apply the silicone bead to each corner where pieces of glass meet. You’ll stay out of each other’s way if you do the entire bottom first, then hit the corners. As your friend applies the silicone, follow behind and smooth it with your finger. Dipping your finger in rubbing alcohol will make it glide over the silicone more smoothly – you get a better “feel†for the silicone that way.

5. When you’re finished, you should have a nice even bead where all of the pieces of glass join. Use mineral spirits and paper towels to get all the silicone off your hands, then follow up with soap.

6. Let the tank dry for at least 48 hours, then use a razor blade to clean up any spills on your glass. The extra silicone should peel off of flat surfaces fairly easily… you’re probably a silicone removal expert by now!

7. Perform a leak/bubble check in your laundry room or outside. Start by putting about 2†of water in the tank. Do a walk around (or just look carefully... mine's a big tank) and look for air bubbles in the silicone. I found one bubble in mine. To fix it I removed about 2†to either side, then patched it with leftover silicone. If there are no bubbles in your base, fill the tank all the way and look for bubbles in the corners.

8. If you’re going to do a second coat just to be safe, now is the time. Repeat steps 1-7. If you apply the silicone thick enough the first time, a second coat should be unnecessary.

Good luck on your project!
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