How to Fix a Leaking Aquarium Without Draining? – 6 Steps

how to fix a leaking aquarium without draining

A leaking tank is inevitable and one of the worst problems, mostly due to the failure of the aquarium sealant. This issue can harm your fish and other critters in the fish tank. Therefore, these incidents need to be handled right away.

How to fix a leaking aquarium without draining? Most of the sealant is silicone, so the quickest way to fix a leak in a fish tank is to strip off the old silicone seal along the seams and paste a new one.

Let’s keep reading to learn how to fix aquarium leak without draining them in detailed steps.

Step-by-step to Fix a Leaking Aquarium Without Draining


A leaking aquarium is so annoying for those who have carpets at home, but it’s an inevitable problem. In general, there are two most common ways to repair a leaking tank. That is to fix from the outside and from the inside of the aquarium.

While repairing a leaky tank from the outside does not require flushing, repairing from the inside may require little or full draining.

Now let’s see what we should prepare before doing leak repair!

What to prepare

Here are all these tools you may need to repair aquarium leak!

  • Waterproof silicone sealant
  • A clean bucket
  • A razor blade scraper
  • A caulk gun
  • Acetone
  • Old cloth (soft paper)
  • A holding tank (to keep your fish temporarily)

A glass aquarium is quite easy to be worn and cracked which causes the tank to leak. Fortunately, it can be fixed with the right direction.

Step 1: Remove some of the tank water

Inspect the leak spots to see if you need to drain partly or entirely water in the tank to fix them.

If the tank leak is positioned at the top of the aquarium, just remove some water until the leaking spot is not submerged in the water anymore. In case the leaking spot is too low, draining a large amount of water is unavoidable.

To be safe, transfer your fish to an empty tank temporarily before removing the water.

Step 2: Remove the old Sealant


Generally, a damaged aquarium sealant is the most common reason for an aquarium leaking; therefore, you need to scrape it by using a razor blade scraper. This tool is helpful for peeling off the sealant without scratching the glass surface.

Please remember to shave off all the old sealant inside the tank that helps the new one stick properly to the tank. And never push the razor blade too hard into the old sealant, which can break the seam between the two tank glasses.

Do this carefully, and make sure not to drop any sealant into the tank water.

Step 3: Clean the Leaking Spot


After removing the broken sealant, the next step is to clean the leaking area properly. Doing so will get rid of all the rest of the old sealant and clean the dirt around the leaking area.

Apply some acetone to a soft cloth or paper towel, gently rubbing the area.

After cleaning, leave the leaking spot to dry for about 10-15 minutes.

This step is essential for leaking fish tank repair since the new silicon only can stick firmly to the tank glass if the area is properly cleaned. If the new sealant is not sticking well, you may have to reseal a fish tank in no distant time.

Step 4: Seal the Leaking Spot


It is advisable to use a caulk gun to run a line of new silicone along the leaking area from inside the tank. Don’t seal an aquarium from the outside, this method is less effective and only short-lasting.

Afterward, you can use your finger or a sealant tool to flatten and shape the newly applied silicone from one end to the other.

Tip: As fish are sensitive, doing fish tank crack repair needs to be careful. Make sure the type of the new silicone sealant is 100% non-toxic.

You can do some research to buy quality aquarium-safe silicone as some brands sell silicon that contains fungicides, which can kill your fish and poison the aquarium water.

Step 5: Give the New Sealant Enough Time to Dry


After all the above steps, you need to leave the sealant to dry fully for 24 to 48 hours. Remember, never refill the water in an aquarium with an uncured sealant if you don’t want it to start getting soft and peeling off.

In fact, you can speed up the drying process by using a heat lamp, but it’s better to let it gradually cure.

Step 6: Fill your Aquarium with Water to Check for Leaks

The ultimate step to stop water leakage from fish tank is to refill the fish tank gradually with clean, fresh water and monitor the leak.

It is recommended to gradually and gently fill the tank with water in it to avoid sudden water pressure on the leak. After this step, all you have to do is to observe the leak in the aquarium for about 24 hours.

Once you ascertain no more leaking spots, you can redecorate and let the inhabitants back in the fish tank.

Why Does the Fish Tank Leak

There are several reasons why your fish tank could be leaking, such as:

  • old sealant
  • tank construction problems
  • pressure irregularities
  • aquarium tank crash.

However, the most common reason is because of the broken sealant.

The water can leak out of the aquarium when the silicone sealant in the seam areas is damaged and worn out after long use.

Leaking spots can be anywhere in your aquarium, and differently positioned leak spots require different methods.

If you see a fish tank leaking from bottom, full draining is inescapable, while you can do a little water removal if the spot is near the top of the aquarium.

On the other hand, it’s not rare to see a new fish tank leaking. As a beginner, you may accidentally buy a new tank with a tiny hole in the tank surface that the naked eye can not see. Over time this spot is constantly exposed to water and worn away, leading to leaks.

Signs to Know if Your Fish Tank is Leaking


The most common sign of a leaky tank is that the water level in your aquarium gradually drops and then stops at a certain point.

Some leaks are so small, making the water trickle down so slowly, that it’s hard to notice right away. Therefore, aquarists should check the aquarium regularly to see if the aquarium has any problems.

  • The easiest way to identify the leak is to use an aquarium leak detector.
  • You also can traditionally use a pen to mark the water level on the tank’s glass to check.

If the water level is continuously dropping, there is a leaking spot somewhere. If not, your fish tank is still working well.

And to locate precisely the leak, you need to fill the tank with more water. After the water level rises, wrap a paper towel around the aquarium. Let’s observe closely, the part that gets wet right away can be a sign of a leak.

Once you have identified the leak, mark and seal it with a good new jar sealant.

How to Prevent Leaking in a Fish Tank

Follow these guidelines for aquarium leak prevention!

  • The first thing is to purchase a good-quality tank from a trusted shop.
  • When buying a new fish tank, it’s essential to carefully check the aquarium’s sealant.
  • Be sure to install the aquarium properly. The tank must be put on a flat and regular surface to avoid cracking. Otherwise, the lower corner of the fish tank will take more pressure than others, leading to leaking.

After all, the age of the tank also can be a reason. The older the fish tank is, the higher chance your aquarium can get leaking problems. Your aquarium starts showing some problems after 7-10 years old.


How to fix a leaking aquarium without draining? Leaking water tanks can be fixed with simple steps and leave no major damage if detected correctly.

It is important to use a new high-quality sealant to repair the leak, which can help prevent a new one.

This problem is inevitable, especially with old tanks, so you must regularly check the aquarium to take timely measures.