How To Reseal A Fish Tank: A Step-by-Step Guide

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You’ve just cleaned your fish tank and are about to put the fish back in, but you realize that the seal around the top is a little bit loose.

If you don’t fix it, water will slowly seep out, cover your floor in water, and your fish will die.

It’s not a good feeling when you realize that you have to reseal your fish tank. But, on the other hand, maybe you were too busy last time and forgot to do it, or perhaps you didn’t know-how.

But now that you’re reading this article, you’ll be able to fix the seal on your fish tank in no time!

Follow these simple steps, and before you know it, your aquarium will be watertight again!

How Do You Reseal A Fish Tank?

Once you have ensured that there are no cracks or leaks in your aquarium’s glass itself (which may require some thorough searching), simply follow these steps:

1. Drain The Water

Make sure all water has been emptied of your fish tank.

2. Remove Equipment & Decor

Remove all gravel, decorations, and other objects inside your fish tank. Place these items in a safe place while the tank is being resealed to be safe from dust or accidental breakage.

3. Clean The Tank

Use a clean cloth to wipe all interior glass surfaces, seals, and edges thoroughly.

4. Remove Old Sealant

Remove any old or deteriorated sealant using a razor.

5. Apply Sealant

Apply a thin line of aquarium-safe silicone around all the corners and edges of your fish tank.

6. Remove Bubbles

Make sure there are no air bubbles by patting away any excess with a dry cloth.

7. Let It Dry

Once the excess has been removed, wait at least 12 hours before refilling your fish tank.

However, if you would like added protection from leaks, you can wait 2-3 days to cure properly.

8. Add Water, Test For Leaks!

Finally, refill your fish tank with water and let it sit for a few hours, and monitor for any leaking.

Tools Needed To Reseal A Fish Tank:

These items are not strictly necessary but can make the process of resealing your fish tank much more manageable.

  1. Clear Aquarium Safe Silicone
  2. Plastic Spreader (such as this one )
  3. Razor
  4. A lint-free cloth

Tips And Tricks For Resealing A Fish Tank & What Not To Do!

Do NOT use household silicone products such as Bath & Kitchen Goop or All-Purpose Goop because they will not hold up against the pressures of an aquarium’s water system and could result in leaks or even flooding inside your home!

These types of sealants may be appropriate for household DIY jobs but should never be used on aquariums.

An appropriate product for this application is an Aquarium Safe Silicone (available here ) which has been specifically designed to hold up against aquarium water.

Never use tape or other household adhesives! These will stick to your glass and sealant and may cause leaks over time – such as tape sticking to silicone.

The best materials for wiping away excess silicones are paper towels, tissues, and lint-free cloths.

What Causes Fish Tanks To Leak?

There are many reasons why your fish tank may be leaking.

For example, improper installation can leave gaps in the sealant that allow water to seep out of the fish tank and into the surrounding area.

Age is another reason your aquarium might leak. Over time the sealant will deteriorate, peel off and eventually spring a leak.

Regardless of how well it was installed initially, you should check your aquarium for signs of leaking every month.

How To Identify A Leaky Fish Tank

1. Visual Inspection:

Visually inspect the empty tank to see any cracks or chips in the glass.

Next, check the sealant to see bulging, lifting off, or mold.

2. Use A Moisture Meter:

Check water levels around the tank using a moisture meter – this will help you narrow down any small cracks that may not be visible to your eyes.

3. Look At The Silicone:

Check the silicone surrounding the tank to see if it is dry, bubbling, peeling, or moldy.

4. Look For Deformities:

Check for bulging or mold on any exposed sealant and immediately replace any exposed or deteriorated sealant.

5. Leak Test (for new setups)

Fill up the tank with water and check for leaks using the methods above.

You can also add rocks, decorations, and other objects that would put pressure on the sealant to see if this causes any leaking.

Look for signs of leakage around the tank – check around the sealant and in areas where the bottom of the aquarium meets your stand.

What Type Of Fish Tanks Can Be Resealed?

Any glass or acrylic fish tank can be resealed regardless of size, shape, or specific make/model.

The most critical part of resealing any aquarium is ensuring no cracks or leaks in the glass itself.

The best way to check for any cracks is by looking at the corners and edges of the tank – if you notice even a tiny hairline crack, it must be fixed before continuing with this process!

When Should A Fish Tank Be Resealed?

A common mistake among owners of older aquariums that have not been sealed is to wait until the tank leaks before resealing it.

However, you should never do this because there are already severe cracks in the glass that need immediate attention by the time a fish tank begins leaking!

Common signs that your fish tank needs resealing include warping or indentations on the glass leaks around connections between tanks and filters, cloudy water due to prolonged exposure to air, mold/mildew growing inside the tank, etc.

Common Mistakes When Trying To Reseal A Fish Tank An How You Can Avoid Them

The most common mistake when resealing an aquarium is applying too much silicone at once – this can lead to messy overflow since the silicone will be thicker on some surfaces than others.

You should apply a thin, even layer of silicones with no bubbles.

Another common mistake is failing to remove all excess sealant within 24 hours after it has been applied, which results in leaks down the line due to adhesion failure.

For best results, allow your silicone time to cure properly before refilling your tank!

Why Should I Seal My Fish Tank?

Sure, it’s time-consuming to reseal your fish tank, but there are some reasons why you might not want to wait:

When an aquarium is unsealed, it becomes more prone to water loss, leading to damage or corrosion of electrical equipment such as heaters and power filters—loss of tropical fish due to the sudden temperature change.

Best Time To Reseal Your Fish Tank?

It’s best to reseal an aquarium BEFORE it starts leaking (and definitely before the water has to stand for more than 24 hours) since that will make the job easier.


A fish tank can be resealed with a relatively easy and inexpensive process.

Anyone responsible for the care of an aquarium should know how to do this, but it’s always best to learn from someone else or read up on what not to do if you’re unfamiliar with the process.

The article we’ve provided has given great tips and tricks and has even shown people’s common mistakes when resealing.

If you’re thinking of resealing your tank, we hope this article was helpful!


How much does it cost to reseal a fish tank?

Prices can vary from store to store, but resealing a fish tank often costs anywhere from $35-$100, depending on the size of your aquarium and how much sealant you need.

Is it worth resealing a fish tank?

This depends on the size of your aquarium!

Small fish tanks rarely need resealing, but large aquariums can be pricey, so it’s always best to check before buying some sealant.

Also, you don’t want to wait until your tank starts leaking water since that will make the process much more difficult and expensive.

Can fish tanks be resealed?

Yes! Fish tanks can be resealed easily in most cases, even if the sealant already in place is old and outdated.

Do I need to clean the fish tank before resealing?

No, a dirty interface is much easier to reseal since the sealant will bond with dirt in addition to the glass.

Sealed tanks should always be visually clean and residue-free before being restocked with fish or water.

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