Why Do Fish Tanks Crack—How Do You Fix A Cracked Fish Tank

By Eddie Waithaka @aquariawise

Why Do Fish Tanks Crack—How Do You Fix A Cracked Fish Tank

You may have a beautiful display aquarium that is breathtaking while it lasts, but if the glass breaks, it will leave you with an awful taste in your mouth.

Sadly, cracked glass on a fish tank is not entirely far-fetched. You may have everything Ok one moment, and the next minute, you be fighting to save everything you can in the room.

And most times, it’s not so much the loss of your fish and the tank you’ll be worried about, but your furniture, flooring and any electronics close to the floor.

So, why do aquarium glass crack, and how can you keep yours from breaking?

The most common reason for aquarium glass breaking is uneven or unstable bases or stands. For that reason, leveling your fish tank before adding water is recommended.

Make sure the fish tank does not wobble or dip even if you move it.

That said, aquariums glass is also said to crack due to a temperature difference in the tank, albeit rarely. A cleft may develop from adding cold water in a heated tank or warm water in a cold-water aquarium abruptly.

Moreover, if you keep your tank in a non-heated room, especially during the colder month, it may cause structural degradation in tropical aquariums, but this type of cracks are only common when you live in regions with extreme weather..

One other reason your fish tank glass might crack is because of general defects during production. Luckily, reputable manufacturers have a guarantee, though that may only be a fraction of the loss incurred from water damage, including on items in your house separate from the tank setup.

Lastly, there is a common belief, and rightfully so, that rimless and glass tanks are more prone to breakages than acrylic aquariums. Essentially, acrylic tanks only come apart because of poor plastic welding (solvent welding) or if the joinery is faulty, meaning everything was not perfectly square and level at assembly.

For more insight on this topic, including how to fix cracks on fish tanks, please read on!

How Often Do Fish Tanks Crack?

There is definitely no definite frequency on how often fish tank glass cracks because the experience is different for each aquarist. Besides, some fishkeepers are more careful and better informed about the topic than others, meaning they can get ahead of the situation where need be.

You could have one aquarium owner having a tank for more than 10 years, moving several times, even cross-country and with the tank full of gravel and a little water, and still not have as little as a hairline crack on the tank.

On the flip side, another aquarist may have a new setup that is barely a few months old cracking. Maybe they dropped a rock in the tank too hard or drilled their fish tank at a wrong angle.

Trust me, it happens!

Thus, the closest I can get to an answer is, “It’s not uncommon for fish tanks to crack, though it does not happen all too often and when it does, it’ll most times a hairline crack at the bottom or side of the aquarium, as opposed to a huge break or a catastrophic burst.”

How Often Do Fish Tanks Explode (Burst)?

If aquarium cracks are infrequent, then fish tank explosions or bursts are rare. Six years and two tanks, I haven’t had one burst happen to me.

In fact, the only place I’ve gathered that aquarium explosions are a thing is the internet.

For that reason, I’ll take a very huge leap of faith and say that more than 85 percent of fish keepers will not have a fish tank explode in their fish keeping life. Unless it’s done intentionally of course, why anyone would do that beat me though.

That said, it’s also good to appreciate that maybe the reason fish tanks explosions are not reported as much is because many hobbyists get ahead of any sort of crack on their fish tank before it gets out of control.

h2>Hairline Crack in Fish Tanks

A hairline crack in fish tanks is a tiny cleft that sometimes develops in the inside or outside of the glass, especially at the bottom, edges and in the front of the aquarium.

Usually, hairline cracks are a few inches long and can easily be confused for a scratch, thus are quite often overlooked.

The easiest way to be sure whether what you have is a hairline crack is to look at it as you slowly change the angle of your vision. If you notice the depth of the mark going through the glass as you move your head, that is most likely a hairline crack.

A scratch will only become less visible as you shift the angle of your vision.

That said, there is a common misconception that when it’s a crack, you should be able to feel it on both sides of the glass. Well, it’s not exactly a misconception, but a half-truth.

The fact is while a crack on the glass will definitely feel deeper when you touch it with your finger and may go through the glass, it’s also possible that you feel it on the outside or inside, and only notice it on the other side once it gets bigger and deeper.

During the early stages of the suspect crack, try putting some tape at the bottom of the mark if you are not certain whether its a hairline crack to see if it gets bigger over time. As you would expect, a scratch will remain the same size, but a stress crack will grow bigger from the pressure caused by the water pushing on the glass.

How Does a Hairline Crack Develop in A Fish Tank?

If you have a hairline crack in your fish tank, there are only several ways this could have happened.

Most times, especially if the fissure is on the bottom of the glass, the hairline crack is from an unstable stand, which causes uneven stress on the glass. Even so, if you are not careful when placing decorations such as rocks in your tank, you risk cracking it.

From my experience, cracks on the glass edge either at the front, sides, or back are caused by drilling mishaps. So be sure to put a layer of tape on both sides of the glass before drilling.

Also, make sure you are not jittery with the drill and get the right angle, this way you won’t have any chips or cracks.

The last cause I think would cause a hairline crack in aquarium glass is pressure from the water column particularly if the tank has an inherent weakness from when it was made.

How Do You Fix A Cracked Fish Tank (Including Hairline Cracks)

Im sure you are wondering whether it’s possible to fix a cracked fish tank. Well, there are a few ways to do this, but you might want to replace your tank if it’s not too expensive or custom, as no fix is completely failproof.

Cracks on large fish tanks are especially hard to fix because of the water column pressing on the glass, which means the cleft will keeping coming back and may you eventually end up with an aquarium burst and a flooded house.

Brekages on the side and front glass are also quite challenging because the best process involves using a piece of glass to patch up the old one, which is possible on the bottom pane because the substrate will sit on it, so the fix won’t look too odd. Something that is not feasible on other parts of the tank.

If you are not in a position to purchase a new fish tank, you can get a cheap one on craigslist or e-bay to hold your fish until such a time when you are ready (financially) to replace it with a tank of your choice.

With that said, it’s also essential to note that fixing a fish tank is quite easy and does not take much effort, more so when making a small aquarium (below 30gallons).

So, how do you fix a cracked fish tank?

Step #1 — Move Your Fish

I know you are thinking about it, so let me clear the air.

It is virtually IMPOSSIBLE to fix your fish tank with the fish in it, especially when its the bottom part that is cracked, and you have any decent chance of doing a good job at it.

Therefore, the first thing you’ll want to do is find a temporary home for your fish, moving them only when you are ready to start the fix. As you would expect, replicating your aquarium environment in the holding tank is highly recommended to ensure your fish are safe and comfortable.

Step #2 — Remove All Decorations and Drain The Tank

Step is pretty straight forward, carefully remove any decorations in the tanks and equipment like filters, heaters, and air pump, then drain the water from the fish tank.

Use an appropriate container to empty your tank, and avoid any draining method that would put more strain to your already fragile fish tank.

Especially do not put pressure on the crack as you might end up with two separate pieces of your fish aquarium.

When you’ve completely drained your tank, I recommend you dry it with a clean hand or paper towel because you will need the adhesive you use later to stay.

Also, if there is grime around the crack, gently clean the glass with white-vinegar all around the cleft both inside and outside.

Step #3 — Get A Tube of Aquarium Safe Silicone Gel

Now its time to make a trip to your local fish store for some silicone. Even so, note that most adhesive gels in the market are formulated with a lot of chemicals as they are meant for use in environments with inanimate things.

So make sure the silicone gel you get is safe for aquarium use with both fish and plants. Moreover, you want a product that isn’t affected by being continually immersed in water.

Usually, I go for silicone products made by businesses within the aquaculture space such as Aqueon silicone sealant.

When fixing a crack in the bottom pane of your fish tank, you will also need to get a piece of glass, that’s the full length of your fish tank bottom when aligned in the direction of the crack. This will make sure the pane support your whole aquarium base and while it covers the cracked portion.

Step #3 — Patch Up The Crack

Start by positioning your tank appropriately, then if you are going to patch it with another piece of glass, place it on the crack allowing it to overlap the cleft by a few inches.

I recommend using a piece of glass that is at least six millimeters thick because it’s is durable and thin enough for such use.

Once you’ve set it properly, patch the piece glass on the crack with silicone and let it cure for 24 hours and you are done.

So exactly how does the patch work?

Well, now that the bottom pane is fully supported, the crack will not flex and pull apart and can no longer leak. After that, the patch is completely safe, and the tank is good as new.

That said, it’s not feasible to use a piece of glass to patch a crack on the side or front pane. The only thing you can do is to place the silicone gel tube inside a caulk gun and apply a thin layer of the gel to the crack.

After that, wet a finger and smooth it down so that it fully seals the area. Do the same on the outside of the glass.

In conclusion, it is only fair that I let you know you may need to change a whole pane, especially if the side or front has a large crack. My rule of thumb is to try and fix the glass with silicone for hairline cracks, use a piece of glass to fix bottom glass, and change the whole pane for deeper cracks that are on both sides of the glass.

Consider getting a new fish tank fixing the glass is going to cost you almost as much as buying a pre-loved aquarium.

That’s all for this post.

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