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How to Fix a Scratched Aquarium

EverydayGreen is a serious DIY addict and has practiced green and frugal living her entire life. She is a freshwater fish enthusiast.


How Deep Is the Scratch?

When determining how to remove scratches on the inside of a glass aquarium, it is important to consider the depth of the scratch. If the scratch inside of your glass fish tank is deep enough that you can catch your fingernail on it, you have a tough fight on your hands.

A shallow scratch can be buffed out with a slurry of cerium oxide where a deeper scratch will need an application of liquid glass. Either way, unless the scratch is more than halfway up the tank, you will need to find temporary housing for your tank's inhabitants.

Buffing out Scratches

When the scratches on your aquarium are shallow a simple buffing process will take care of the problem. You will want to use a drill or rotary tool equipped with a rubber buffing disk and a shammy pad. Rotary tools are far easier to work with in the confines of the tank.

Step 1: Drain the tank.

If the scratch is above the 50% watermark you can cover the remaining water with a plastic bag and tape it off with masking tape to prevent any of the glass dust from getting into the tank. If it is below the 50% mark you’ll need to temporarily house your fish in another location. You still have to put it in the plastic bag and tape it off to keep glass dust from getting mixed into the substrate.

Step 2: Mix a slurry of cerium oxide.

You can get it online from jewelry supply stores relatively cheaply. About half a pound will be plenty to do the job. Or you can purchase a premixed solution directly from

Step 3: Apply the Slurry directly to the scratched area and buff for five minutes.

Wipe the area clean with a rag. Repeat until the scratches are completely gone (this may take several hours depending on the depth of the scratches).

Removing a Scratch With Liquid Glass Resin

With the advances in liquid resin technology, it is now possible for car windshield cracks to be repaired with an injection of a special liquid resin that has the same optical refraction properties as glass. This same resin can be used to fill in deep scratches in a glass aquarium. One do-it-yourself glass windshield repair kit will take care of all of your problems.

Step One: Clean the Area

Wipe the area around the scratches with a cotton swab dipped in alcohol. This is important because any lingering impurities may hinder the resin's ability to set.

Step 2: Fill the Syringe

Mix your liquid resin as per your package directions and fill the syringe that came with your kit.

Step 3: Carefully Fill in the Cracks

Wait for 24 hours to make sure it has cured then buff down the excess resin with a buffer like the one in the previous section, making sure to cover the water with a plastic bag to seal out the resin dust.

Tips and Tricks

When you are thinking about removing scratches, it is important to know which method will work for you. If a scratch is too shallow, the resin in a syringe may not fill it; conversely, if a scratch is too deep, then buffing will not only take a very long time it will also compromise the structural integrity of the tank.

It is always important to keep yourself safe while doing this kind of repair. Wearing a dust mask is highly advisable because glass dust is extremely sharp and can cause irreparable damage if inhaled. Glass dust is very similar to silica dust and can cause pulmonary problems very similar to Silicosis.

In smaller tanks (55 gallons or less), it can be very hard to fit a drill with a buffing pad inside. It is much easier to use a rotary tool like a Dremel for this type of application.

Now that you know how to remove scratches on the inside of a glass aquarium you don’t have to cringe the next time your Plecostomus starts dragging gravel against the glass.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.