WHY DO FISH TANKS CRACK? What to do when your fish tank leaks.

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A lot of things can happen that will lead to why do fish tanks crack. No matter how careful an individual is, there is nothing like a perfect safety trend or behavioral pattern, accidents are bound to happen.

Its a natural order of life that can’t be ridden, a lot of things can happen that will lead to damage of your aquarium tank.

Instead of having to break your budget to order for a new aquarium, you can bank on aquarium glues to help fix your aquarium glass and your aquarium will be good as new again.

When an aquarium cracks there would not only be the destruction of aquarium and death of the fish even your furniture and flooring would just be an awful mess. It is good that you know why do fish tanks crack and what can be done to avoid this from happening in the first place.


Why do fish tanks crack?

Fish tanks crack mostly because of two reasons. One is because the manufacture of the tank was in poor quality and the silicone is not working as it should. The second reason is the aquarium stand is not level. An un-level aquarium causes undue stress on one location of a tank creating cracks.


  1. Poor manufacturing.  If a tank is not sealed properly with a strong bonding silicone, the glass panels can pull and tug on the joins causing cracking or separation and ultimately leaking. Another sign of poor manufacturing are aquariums made of glass that do not have thick enough glass. Always purchase aquariums from trusted dealers with solid reputations and ratings.
  1. An un-level base. This is probably the more common issue of cracking tanks. If your aquarium stand is not level, your tank will not be level. This means the weight is shifted towards the lower part of the tank. The stress on the glass could be enough to cause cracking. It might be hard to get the tank to a precise level but that’s okay because being off just slightly can be remedied with a rubber pad or styrofoam made for this application.

3. cutting off the PVC edging around the tops of aquariums to give them a cleaner look. As nice as they look after, without the         extra plastic trim around the edge, the trim is there for a reason. The reason is to provide support for the glass walls of the aquarium. So why purposely weaken the strength of the tank? If the plastic trim doesn’t appeal to you, then purchase a different tank.




Yes, glass breaks and your aquarium will leak wherever there is silicone. Some larger aquariums will have what is called a center bridge. Essentially it is a support spanning from front to back located top center of tank. It helps to support the structure because a full aquarium is extremely heavy. If there is even the slightest of movement, there is a lot of weight pushing against the glass.

I have found that a tank is more likely to leak first, giving you time to repair it versus a full on break in the glass. If it was a common event, glass aquariums just wouldn’t sell.




If aquarium glass breaks, things are going to get wet. If it’s just a crack and the tank only leaks, consider yourself lucky. Just make sure to empty the tank before glass breaks away. Everyone has seen the terrible video clips of big tanks breaking and water flowing out, destroying everything! I don’t think a tank at home will be that dramatic, however, it can cause some damage.

Luckily for aquarium owners though is that tanks usually leak first along a seam before it will ever straight out break. Not to say that that doesn’t happen because it does.




This is super easy. Once a month, check on the outside of the tank along every seam that has silicone. Check for droplets of water. If you spot any, you might have a leak. Visually check the glass as well. If it’s a new tank you will have to fill it to find leaks.




No, if it’s cracked glass, I wouldn’t even try to fix it. Empty the tank immediately. You could try taking off the cracked panel and getting a new piece of glass or, for the price of a used tank, just buy one of those. It’s up to you.




As previously mentioned, to take preventative measures, make sure to purchase aquariums only from reputable manufacturers. Leveling the tanks base properly, is another great way to stop a tank from leaking.



I don’t know of any statistics for fish tanks exploding. All I can tell you is I have never had it happen to me and I have never heard of any of my local fish stores talking about any of their tanks exploding. It obviously doesn’t happen very often.


If you purchase a good tank and take the necessary precautions to set it up level and correctly, you shouldn’t ever have an issue.




If you find that the silicone has a leak, the best thing you can do is empty the tank below the area that needs to be resealed. Scrape the old silicone off and, using a safe for aquarium silicone, apply some on the seam wiping it down a bit with a wet finger to smooth it out.

If it doesn’t appear that there is a very big leak then you can keep water in the tank below the repair but if the whole length of silicone from base of tank to the top needs to be scraped off and resealed, you are probably better off emptying the tank completely and putting the fish in another tank until the repairs are complete and their tank is ready for them again.


Best Glue For Aquarium Glass in 2020

1. Clear Aquarium Silicone Sealant

Clear Aquarium Silicone Sealant - 10.2 Fluid oz Cartridge


The clear aquarium silicone sealant from ASI has been made especially for aquariums. The sealant creates a form of tight seal that is not affected by being dipped into water continually, and the better part of this is that the sealant can operate in both fresh and salt water

Most sealants require the use of primers for better firmness but not this one because of its high-end quality.

You can bet on this sealant not cracking or shrinking, and it will still continue to give you a lasting bond for your aquarium. Another added advantage is that you can use this sealant in a vertical mode and you won’t have to worry about any form of sagging and or flowing as the product cures.

In terms of curing, the product’s total cure time is about 7 to 14 days, after this stage, it becomes totally nontoxic to your fishes. Lastly the sealant is clear and would not disrupt the look of your aquarium.

UV radiation, ozone or airborne chemicals have no fight against this sealant because it is 100 % silicone and this makes it resistant to all the above natural enemies.


2. Aqueon Silicone Sealant

Aqueon Silicone Clear

This is also a 100% toxic safe silicone, and it is very easy to apply to your aquarium tank. The Aqueon silicone sealant forms a permanent and super strong seal that will help guide against leaks.

This sealant will last for a long period and still, it won’t crack or shrink. Because this sealant remains nontoxic during its curing time, then the safety of the aquarium and the fish is all guaranteed.

This product is genuinely durable and permanently flexible. You are advised to give the product a period of 24 to 48 hours after application before use.

Overall this is safe to use silicone with the strength of a typical high-end quality sealant.


3. Aquascape Black Silicone Sealant

Aquascape 22010 Safe for Fish, E

In the case of this type of Aquascape black silicone sealant, you do not get a clear sealant as the name also implies.

If you need a type of sealant that will help patch your pond liner or fix a leak and you seek a black and not clear sealant, this is your best pick.

This is a black type of sealant that is purely made from silicone; it forms a strong and watertight seal even with exposure to water for a long period. The black color forms a blend with liners and fountains which cause for an invisible repair.

You can use this 10.1-ounce tube with your caulking gun for smooth and faster application.

In terms of curing, you can begin use of the product after the curing phase. Note that this product is safe for plants fishes and any other marine life species.




A newer material that is being used for aquariums now is acrylic. Acrylic is lighter than glass and stronger. It is also more expensive than its glass counterpart. Acrylic tanks should not leak as they are all one piece where a standard rectangular glass tank is 5 pieces sealed together.


So if you have the money for acrylic, I would definitely go this way. I have a really nice acrylic tank listed on my recommended aquariums page which can be found through this link.



You should have a really good grasp now on why a fish tank would crack along with some knowledge on how to start your tank properly to prevent cracking. Level the base of the tank first before filling the aquarium. A little bit of prep up front will save you a lot of grief down the road. Good luck, fellow hobbyists and happy fish keeping!

Related Articles:


Best Silicone To Use For Aquarium



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