Why do fish tank cracks

Why Do Fish Tank Cracks and How To Fix Cracks?

Introduction to Aquarium Cracks

You care about cleaning your aquarium or just gazing at the amazing sight of your cute little Bettas or Gold Fishes swimming happily around the full width of the tank. But, all of a sudden you may spot a crack on your fish tank or glass split parts on the surface of the glass. You might also see some water drops seeping through the glass surface. This is the moment when you get introduced to Aquarium tank Cracks. Gasp! And you start to think about what to do next.  Fisk keepers who live in extreme conditions and temperatures can easily relate to this phenomenon. Every year when there is a seasonal change, the surrounding temperature changes extremely. When tanks are not heated and kept at proper temperature, it causes these fine cracks in them. Some Tanks may be defective since they are manufactured. You might have not noticed it at the time of buying. As the time passed, pressure and temperature changes would have caused these tanks to crack up more. Most tanks on the market today provide a warranty on manufacture and will replace defective Tanks within the warranty cover time for free. Glass rimless Aquariums are wonderful to sight and also wonderfully prone to damage. This is because of the fragile nature of glass joints. On the other hand, acrylic tanks are much more durable and have tougher joints (Plastic Welding) compared to rimless aquariums. Sometimes, the damage caused by leaking of water on nearby electronic appliances and floorings may be much higher compared to the replacing cost of tanks. In this blog, we will completely explain how various cracks develop over a period of time on tanks and how to fix the cracks on fish tanks and home Aquariums. So, sit back, relax and enjoy the reading.
Fish tank cracked, Fish tank cracks

Why do fish tanks crack? 

The major reasons for the surface of fish tanks to crack are caused mainly due to the uneven distribution of weight of the tank on the surface the tank is placed. Leveling the tank before adding water will solve this problem. There are few other reasons too that cause Fishtank cracks. Glasses are highly fragile products and they can easily be affected by temperature, pressure, and other external factors. A variety of changes inside and outside of the tank causes Hair-like cracks called Clefts. 

What causes clefts on fish tanks?

Addition of warm water inside cold tanks or pouring cold water in hotter tanks immediately without letting the tank to cool causes cleft formation of fish tanks surfaces.

Do Fish Tanks Crack Often?

Fish tanks are glass products, and any glass product is easily prone to wear and tears. How we handle our tanks plays a major role in maintenance of our fish tanks. Some people keep their ancestral glass products for hundreds of years and some break glass products now and then. This may be because of less attention to taking care and handling glass and acrylic products. Just like that, we know some Fish keepers and Aquarium enthusiasts who had kept their giant 50 gallon tanks crack and scratch free even after miles of transport and tank alterations. We have also witnessed some tank keepers who had seen hairline cracks and Clefts formed on their tanks’ surfaces within months of buying. As a whole, we didn’t find a comprehensive data study on how often fish tanks crack up and develop clefts over a period of time. It purely depends on how people take care of and handle their aquariums. With little care, while handling, you can easily maintain fish tanks and aquariums like brand new for years.

Do Fish Tanks Burst Open and Explode?

Fish tank cracked, Fish tank cracks
Yes, tanks are just like water dams that stop water flow. Stagnant water builds up pressure and when the walls of dams are weak, dams would burst open. Similar is the case of fish tanks, if there are numerous cracks on the surface of a tank, tanks may burst open. We have several tanks of our own but never witnessed this incident for the past 7 years. In fact, it almost never happens for more than 90% of professional aquarists and fish-keeping enthusiasts. We had come across tanks burst open or explode. This is mainly due to improper maintenance inside and outside of the tank that causes numerous hairline cracks leading to break open of water pressure. So, we can clearly state that it is random for fish tanks to burst out or explode if the tank is damage-free and of good quality. Even fish keepers like you after finding any cracks on the tank surface, will definitely take steps to solve it immediately. This is another reason for less fish tank explosions. Spoken about hairline cracks, let’s get to know what hair line cracks really are.

What are Hairline fish tank cracks?

You may notice a small line of damage on the surface of the fish tank. Most people would confuse these cracks as scratches on fish tank surfaces. But actually these are hairline cracks on the fish tank surface.  

What are hairline cracks?

Hairline cracks are small clefts that are a few inches long on the glass surface of fish tanks and aquariums. They can be found at the Front, Bottom, and sides of Fishtanks To differentiate between a scratch and a hairline crack, you can use a torch or phone’s flashlight. When the light is tilted at a certain angle above a scratch, it becomes less visible and at times even would disappear. But, Hairline cracks on the other hand will refract light and show the depth of cleft and damage on the surface of tanks. You can use your hands also to feel the difference. When fingers run over scratches, it feels just like moving over a small strip of thread. But you can literally feel the depth of a Hairline cleft and the depth is directly proportional to the damage caused. Sometimes, hairline cracks affect both the front and back of a panel. Sometimes, hairline cracks on tanks are only on a single side of the tank’s surface. Scratches can be left as such as they don’t cause much damage. Scratches destroy the clean beauty over the length of the tanks. But, it can be avoided by eyes and you will get used to it. A simple remedy for Hairline cracks is to put on a transparent hard tape over the crack to prevent it from further development. If the crack seems to be developing in size, then you must go for treatment. This happens mainly due to the pressure that tries to push the water outside of the tank. The crack develops gradually and if untreated, it may cause a fish tank burst.

How Hairline Cracks Develop in a Fish Tank?

There are few reasons for Hairline cracks to develop in your fish tank. They are 

  • Unstable bottom of the fish tank causing more stress on either side of the bottom of the tank.

This causes uneven distribution of pressure throughout the bottom of the tank. So, at one point, the molecular chain of the glass atoms tends to give up, causing clefts and cracks on the fish tank’s bottom and surfaces. 

  • Rough handling of the tank while shifting and not carefully handling Rocks and Decorations while placed in the tank’s bottom.
  • Improper drilling of the tank around the edges will cause cracks on edges and even in front of the tank.
  • Some tanks may have manufacturing defects. So, since its production, some tanks may be having hairline cracks. These cracks will develop eventually over time.

So, knowing what hairline cracks are and how they occur, let us learn how to treat Hairline cracks and other damages of your fish tanks and aquariums.

How to fix major Cracks, Clefts and Hairline Cracks of fish tank

Cracks…Cracks…Cracks…oh!, So much crack stuff discussed on this blog. Is it even possible to get your tank to a brand new condition? Sorry, but you can’t take the tank back to its original condition as it is a glass product after all. So, if your tank is inexpensive, discard it and buy a brand new crack free one. Also, this method doesn’t work for tanks bigger than 25 to max of 30 gallons. The pressure built up on larger tanks is much higher compared to smaller tanks. So, even after so much effort the crack will eventually develop and may burst open on larger treated tanks. You may go further inexpensive options like buying used but good condition tanks. They can easily be found on online websites and even on local aquariums. But, if you are so much attached to the tank you own now. Then it is time to fix the crack out of this tank. Wrap on some gloves and let’s get our hands dirty!

Steps to fix a cracked fish tank

The following are the steps to fix your beloved but cracked fish tank. 

Transfer Fish Safely

Obviously, it is necessary to transfer the fish from your tank to another safe vessel. You can’t work on with your fishes inside. You may scare your Goldie or Bettie if you decide to go hand on inside to fix the crack Take proper measures to transfer the fish and add adequate amounts of water and oxygen to the vessel in which you keep fish temporarily. Be careful, else your fish would escape and it would turn out to be your own version of Finding Nemo. 

Clear Water, Gravel, and Decorations

Clear heaters, fish tank lights and air pumps off the tank first. These equipment are fragile, so handle with care while moving and operating. Now, it is time to transfer the water slowly from tank to sink or other vessels. Before moving water, you can make work easier by moving the Decorations plants and gravel first. 


 Make sure not to touch the cracked region by any means as it may cause further damage. Sometimes more pressure on the cracked parts may cause the tanks to burst. Hold the tank firmly and lift it by applying pressure on either side. Applying pressure at the single side may cause more stress and Boom…Glass breaks. If the tank is bigger than 10 gallons, Drain the water slowly using a pump or fetch water using a vessel and discard it. You can directly empty smaller tanks by tilting them. But, be careful while handling a full tank filled with water. Once done with emptying the tank, wipe all dirt and dust using a clean wipe towel or soft tissue papers. Don’t use strong soap agents and cleansing agents. It will damage the tank surface. And after treatment, it may change the tank water composition. Better go for mild cleansers and natural cleansers like White vinegar or little lime extract. Now let us go to the patch up process

Buy Aquarium Safe Silicone Gel

Normal Adhesives like hot glue or wood adhesives may cause the nature of your fish tank water. Also, it may turn toxic for the fishes living inside the tank. So, better purchase Aquarium Safe Silicone Gel for fixing tank cracks. Get to your local fish shop and ask for Aquarium Safe Silicone Gel. You can go for products like ASI Clear Aquarium Silicone Sealant and Aqueon Silicone Sealant. They are easily available online and nearby Fish products dealers.

Fixing the tank Crack

Clean up the area where you are about to fill up sealant with acetone. This helps to make the adhesive dust free and stick more efficiently on the crack surface. Now using a caulking gun spread the Silicone gel thoroughly throughout the area. WE advise you to spread a layer on the front and back. Apply a bit more of Aquarium Safe Silicone gel on the back as it pushes the layer outwards, making it stick more and fill gaps efficiently. Allow it to dry for a minimum of 24 hours. You can also use a heat gun immediately after applying gel to make it hold more firmly. But make sure the temperature doesn’t exceed more than 110 degree Fahrenheit. 

Monitor the repair work

Now, it’s time to test if the repair works. Fill up the tank again to full capacity and check for any leakage or water seeping around the treated area. Adding a piece of paper taped over this area makes it easy to discover if there are any further leakages after treatment. Once, if you find there is no more leakage from the tank cracks, you can add your fishers back to the tank without worrying much about the tank bursting out.

Restoring tank decoration and gravel

Now, add the gravel back into the tank. You can clean the gravel before adding it again inside the treated tank. Add the gravel first, and then add rocks over it. While placing the rocks, make sure you do it gently without causing much damage to the bottom of the tank. For that is why we worked so hard to fix it. Then you can add on the decoration objects and plants inside the tank. 

Pro tip

 You can change the location of the plants and decoration objects, which will make the fish more curious and explore the new locations. Finally, add your beautiful fishes into the fishtank and finish the work by fixing back the Fish tank lights, water heater and air pump in its place. 

Conclude with happiness

Now, you can come to a conclusive end of doing great work all by yourself. Congrats mate, you have done a great job.  You can sit back and enjoy the awesome sight of your beautiful fishes swimming happily around the tank. Thinking of adding some new mates to your tank now? Go for it my fellow fish keeper. So, that was our complete guide on how to fix your damaged fish tanks and aquariums. We hope this article has helped you learn how to fix tanks by yourself. Comment below and tell us which was your favorite step and which was the most difficult step to follow. If you liked this post do share it with your friends and family. Cause sharing is caring. See ya! Until then, keep growing your aquarium!

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