Should You Perform An Aquarium Leak Test For A New Fish Tank?

6 min read

An aquarium leak is one of the worst things you can experience as an aquarist. You don’t want to encounter a situation where your fish tank is completely drained of water and your fish have died from suffocation.

No, that’ll be horrifying.


That is why it is important to leak test your aquarium before you set up a new tank. I know you’ll be overly eager to introduce the fish from day one, but you’ll have to be patient and follow the right process.

In this article, we’ll look at how to perform an aquarium leak test and how to fix leaking aquarium.

Let’s get started.

Why You Should Do an Aquarium Leak Test

Most aquarists are obsessed with creating optimal water conditions for their fish, and rightfully so, but what about the water itself?

You want to make sure your fish always have water to swim in right?

More than that, fish can’t breathe outside of water, just like how humans can’t breathe underwater, so lack of water will be a death sentence to your aquatic buddies.

That will be a major tragedy, but that’s not the only issue; water draining to the bottom can ruin your floor, especially if you have a wooden floor.

Moreover, a leaking aquarium can create a myriad of hazards, such as electric hazard, fire hazard, and the risk of slipping.

If it is a small leak, it could go unnoticed, which may lead to a dangerous situation.    

If you are planning to set up an old previously-used tank, then testing for leaks is a no-brainer – you never know how long before the fish tank leaks.

On the other hand, if you are buying a brand new tank, it is still prudent to do a leak test, because, first, manufacturing defects are possible, and second, the tank could be damaged while shipping.

How to Do an Aquarium Leak Test

The very first thing you should consider is where you do the leak test.

Since you are testing for leaks, you should be expecting a small chance of leaks, so doing the test on your expensive wooden floor should be a big no. Do the test in your garage or outdoors.

Once you have found a suitable location and filled the tank up, the next step should be to dry the outside of the tank; you may have inadvertently wet the surface of the tank while adding water, which could be mistaken for a leak.

You can do the following things to identify leaks.

1.    Look for Visible Leaks

If the leak is bad enough, you can spot it almost immediately after you fill the tank with water: look for any dripping water.

If the leak is not too big, you may have to wait a few hours to see visible signs of leakage. Any water outside the tank means it is leaking, as long as you dried the tank surface in the first place.

2.    Look for Cracks and Chips Around the Edges

You can identify potential leaks without even filling the tank with water, by examining the tank itself for defects.

Go through each panel of glass or acrylic for cracks; even if it is minor, cracks have a tendency to spread and cause a big leak.

Also, look around the edges for any chips in the panel – the edges are the weakest points of the whole tank, so any leak is likely to come from those.

If there are any defects, the tank is likely to leak – you can confirm it by adding water and testing. 

3.    Look for Hard Water Stains

If the leak is too minor, you have to put your detective hat on to find it. As you may know, water leaves a trail of stain on the surface where it constantly runs on.

This stain will already be there if the leak developed while the tank was already in use, so if you’re getting a used aquarium, watch out for the stains.

4.    Examine the Silicone Seal for Loose Pieces and Bubbles

Your tank is made up of individual panels of glass or acrylic held together by a silicone sealant. As you can imagine, this makes the seams the weakest points of the tank.

That is why it is important to check the condition of the sealant – if there is any damage to the seal, your tank is more likely to leak.

Bubbles within a seal may also be an indicator that the seal is going to fail, so keep your eyes peeled for it.

How Long to Leak Test Aquarium

So, you are wondering how long you should do the aquarium leak test.

Ideally, the leak test should be carried out for 24 hours to a few days – the longer it takes, the surer you can be of the integrity of the tank.

How long before fish tank leaks during testing depends on how bad the leak is; if it is a major one you can spot it within a few hours, while smaller leaks may take some time to be noticeable.

The test is essentially over once a leak is identified. If not, the test goes on as long as it is needed.

In fact, stress failure can occur anytime, so some say you should do a leak test as long as you have an aquarium.  

How to Fix Leaking Aquarium

It is possible to fix a leaking aquarium, depending on where and how bad the defect is.

If the leak is at the seams, all you have to do is remove and replace the silicone sealant.

First, use a razor or another sharp object to remove the old seal. Do NOT remove the seal between the panels – you are only removing the outside seal.

After you are done removing the old seal, clean any residue with acetone. The next step is to apply a non-toxic aquarium silicone sealant along the seam.

After you apply a bead of sealant, smooth it out using a tool or damp finger. The bead should be a quarter of an inch in width.

It is important that you do this to the inner seam as well as the outer one – in fact, the inner seam is more vital for holding the tank together.

Also, because old sealant doesn’t bond well with new sealant, you have to remove and replace it along the entire seam, not just where the damage is.

After you finish applying the sealant, you must let it cure for 24 – 48 hours.

You would be happy to know that it doesn’t cost too much to reseal a fish tank.

Some Final Thoughts…

Identifying and fixing an aquarium leak should be your top priority, as it is literally a life-or-death situation for your pet fish. And a water leak indoors is a housekeeping nightmare.

If your fish tank is losing water but no leak is identified, it could be simply due to evaporation, so no need to be alarmed. You can expect some evaporation if you have an open-top tank and the weather is hot.

An aquarium leak test is not the only thing you should carry out when setting up a tank for the first time. You should also make sure your tank is properly cycled before you introduce any fish.

That’s it. Make sure your tank is able to hold the required mass of water so that your fish can be safe and happy inside.

Thanks for reading.






Written by:

Pet Aquariums

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