As an avid aquarist, Pete enjoys DIY projects and breeding various species of fish, particularly cichlids, most.

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Learn how to refurbish old all-glass aquariums and make them as good as new.

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Make an Old Fish Tank Look Like New

Knowing how to refurbish an all-glass aquarium is a good skill for any fish enthusiast to have. Have you ever found an old aquarium tucked away in a relative's garage or attic or found a really good deal on one at a garage sale or on Craigslist? If you're like me, you surely have. It's relatively easy to make these old aquariums like new and watertight with a little bit of effort.

Improve the Safety, Too

Refurbishing old all-glass aquariums not only serves to make them like new, but also makes sure that no toxins will be in the tank to leach back into the water and kill the tank inhabitants. Aquariums that have been used to keep reptiles or by people who don't know that soap and other cleaning products shouldn't be used to clean aquariums should always be resealed. It is a good practice when the history of the aquarium is unknown.


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5-in-1 painter's tool

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GE Silcon I 100% silicone 4 pack

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Scraper - single edge razor blade holder

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Box cutter

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Distilled white vinegar

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Supplies and Tools

There are several tools and some supplies that are necessary for refurbishing an all-glass aquarium.


Single edge razor bladesScraperBox cutter5-in-1 painter's toolspray bottle


distilled white vinegarpaper towelsclean rags100% silicone


Only use 100% silicone to reseal all glass aquariums. For example, use GE Silicon I, not GE Silicon II. Some types have mildew resistance chemicals added that will leach back into the aquarium when filled. Do not use any other kind of sealant or caulk as the result will be disastrous.

How to Prepare the Tank

A good start to prepare the all-glass aquarium to be refurbished is to hose it out really well with clean water. Make sure that the work area is clear of any rocks, pebbles, and other debris. Set the aquarium on one of the sides, so that the water can easily flow out.

Do not fill the aquarium with water then attempt to dump it out. Water is extremely heavy, and while aquariums can contain it any flexing can crack the glass and possibly injure you.

Once the aquarium is hosed out, set it upright and pour a little distilled white vinegar in it. Use one of the clean rags to clean the glass and frame with the vinegar. Distilled white vinegar is acidic breaks down hard water stains and other dirt off the glass. Rinse the rag with clean water then add a little more vinegar to the aquarium. With some effort, the aquarium should be sparkling clean.

Distilled white vinegar is used to clean the aquarium since it's easy to tell when there is no residue left (the smell is gone), and it works really well. Any residue dilutes to non-toxic levels when the aquarium is filled as well.

Choose a Soft Work Surface

In order to not damage the glass of the aquarium, it is best to have a clean, soft work surface. A sturdy table with a piece of carpet on top works well. The carpet allows the aquarium to be easily moved and protects it as well.

How to Remove the Old Silicone

Fill the spray bottle with half distilled white vinegar, and half clean water then set it aside.The 5-in-1 painter's tool makes removing the bulk of the old silicone very easy. Use the pointed edge in the corners to scrape out the old silicone. Don't worry about getting the film that is left behind. The single edge razor blades and spray bottle will be used to get that. Use the box cutter to cut the silicone pieces loose from the aquarium then discard them. Be sure not to force the edge of the tool between the glass as chipping may occur.If the aquarium frame has been removed, scrape the silicone from the aquarium that held it in place. Be careful to hold the tool flat against the glass and not on an angle when close to the edge. The tool can easily chip the edge of the glass. Scrape any silicone off of the aquarium frame as well.Once the bulk of the silicone is removed, switch to the scraper with the single edge razor blade in it. If the area of the aquarium you're working on is dry, use the spray bottle to dampen it. This makes it easier to find residual silicone and remove it with the razor blade.Keep working until there is no more silicone residue. This is very important as new silicone will NOT bond to old cured silicone.Once all of the silicone is removed, wipe the aquarium inside and out with a clean rag dampened with distilled white vinegar. It is most likely that you'll discover some more silicone residue. Repeat the process until there's none left.Wipe the tank out with a clean rag and water. Rinse the rag as needed and continue wiping out the aquarium until there is no hint of vinegar smell. Allow the aquarium to dry for a few days.

How to Reseal the Aquarium

Resealing an aquarium requires some patience and finesse otherwise the result will be less than desired. There are different techniques for resealing an aquarium. Some people choose to mask each pane with a rectangle of masking tape 1/2" from the adjoining pane. The tape is removed after the silicone is allowed to cure a short amount of time. Some of the best resealers choose to apply the silicone freehand. Either way, here's a few tips to help with the process.

Keep plenty of paper towels handy to wipe excess silicone from your fingerUse one continuous to spread the silicone and do not go over it againUse a bead appropriate to the aquarium size, but not more than 1/4"

Step-by-Step Instructions

Set the aquarium in such a way that all the seams are easily accessible from a comfortable position. Resealing can be hard on the back if you have to bend over to reach into the aquarium.Mask the seal areas of the tank if desired.Place the silicone in the caulking gun, cut the tip on a slight angle slightly less than 1/4", then puncture the silicone cartridge if necessary.Run a bead of silicone around the bottom inside seams of the aquarium. Smooth each in one motion toward a corner. If you must, stop the motion, then reposition and restart the motion in the same place.Be sure to wipe excess from your finger with the paper towels. This will help prevent getting silicone where it doesn't belong.Run a bead in one corner from the bottom to about one to two inches from the top of the aquarium. Pull the silicone up to the top of the aquarium while smoothing. The space left empty at the top should be covered by the excess silicone. Add a little if needed. Repeat in the other three corners.If you've masked the seal area, allow the silicone to cure for a few hours then remove the tape by pulling it slowly on an angle away from the seal. This should leave a clean, professional-looking line.

Dealing With the Frame

If the top frame was removed, run a bead along the top of the glass then press the frame down on to the aquarium. Use masking tape to secure the frame down by placing a piece over the frame from one side of the glass to the other. Check for excess and smooth it along the frame.

If the top frame was not removed or if it was just reattached, run a bead along the underside of the frame, then smooth it.

If the aquarium has a glass brace, run a bead under it where it joins the side adjoining glass then smooth it.

Don't attempt to install the bottom frame now if it has been removed. It should be reattached after the aquarium seal has cured for 24 hours. Don't move the aquarium until this time has passed either. Reattach the bottom frame by running a bead along the bottom glass edge then reinstall the frame. The excess will press into the frame. Use masking tape pieces to secure the frame until it cures.

Curing and Cleaning Up

Allow the aquarium to cure for a minimum of five days, preferably seven, before test filling it. Test filling should be done outside if possible, just in case your reseal didn't go so well. Make sure the aquarium is on a level surface and preferably on an aquarium stand. Fill 1/4 of the way and wait thirty minutes before filling to halfway. Wait another thirty minutes then fill the remaining half.

The greatest pressure is at the bottom of the aquarium, which is why it is suggested to take longer to fill the first half. Use a razor blade to clean any stray silicone from the glass.

If all goes well, drain the aquarium, rinse it out a few times to be sure any residual vinegar is gone, then set it up in its location.

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.

Questions & Answers

Question: Wondering if you have advice for someone trying to actually remove one of the glass panels? I got a couple of 40 gallon zilla tanks im trying to repurpose into terrariums and i need to remove the front panel to make it into glass doors instead!

Answer: You can remove the silicone around the pane then use a razor blade to get between the glass. Applying very slight pressure while doing that will allow you to get in between the glass. VERY gently cut through the seal. Do not allow the glass to crimp down on the razor blade as cracking can happen.

Question: How can you get the white residue off of the top an aquarium?

Answer: Distilled white vinegar will work most of the time.

© 2010 Nolapete


Nolapete (author) from New Orleans, LA on June 23, 2020:

No, It is not safe to do that.

Ian Daft on June 22, 2020:

Is it safe to stand in the tank as mine is very big, so i can get to the silicone

Nolapete (author) from New Orleans, LA on May 27, 2019:

Every bit of silicone inside the tank has to be removed. Not from between the glass, but inside the tank. New silicone will absolutely not bond to old cured silicone. It must be one contiguous bead that cures at the same time into one solid seal. This is why removing a section of silicone near a leak or putting silicone over old silicone is pretty much 99.99% fail.

Robin on May 27, 2019:

do I need to get all the silicone off or can I go over the little bit that is left if I cover it completely. the beads on the side are small and I'm thinking to do just the bottom completely and cover the sides that are already there. would this work?

Nolapete (author) from New Orleans, LA on May 14, 2018:

Most of the time it serves two purposes; cosmetic and to protect the edge of the glass. If there is a center brace, depending on the thickness of the glass it can be structural. Replacement frames can be purchased from 55 gallon tanks are quite common, so they should have a replacement.

Jeff on May 13, 2018:

I have a 55 gallon long that has been in storage for 20 years. The "frame" has crumbled. Is it for looks or is it structural? I would like to use this tank for a sump. Thanks

Nolapete (author) from New Orleans, LA on April 29, 2018:

A painter's 5 in 1 tool is what has become my goto. I'd clean off as much silicone as possible then work the tool between the glass and frame a little at a time. Don't pry on it much or you risk cracking the frame. It take a lot of patience to get most frames to release. Good luck.

Lecoeur on April 28, 2018:

Hey I have a 120 gallon tank and it was leaking from the top rim and I am having a difficult time taking the rim off. It almost looks like it can’t come off. Please help me out. Thanks

Nolapete (author) from New Orleans, LA on September 02, 2017:

You need to understand that the silicone between the glass and the silicone on the inside of the tank are two separate parts of this. If the silicone between the glass is damaged, it is unlikely that the tank will be successfully resealed without taking it apart. Most of the time this is not the case. To answer your question, you must remove ALL of the inside the tank silicone to reseal the tank. Uncured silicone will not bond to cured silicone. The seal must be contiguous and applied at one time and allowed to cure for 72 hours minimum.

Partha Chakraborty on September 02, 2017:

Hi, you have mentioned under "A common misconception":

A common misconception.........silicone sealant needs to be removed from between the glass panes. This is not necessary and strongly discouraged. Only loose pieces of silicone between the glass should be removed if they exist. Most of the time the silicone bond will still be intact between the glass panes. The silicone that needs to be removed is on the inside of the aquarium. Again you have mentioned under "Removing Old Silicone" Keep working until there is no more silicone residue. This is very important as new silicone will NOT bond to old cured silicone.!!!!

So which is correct?

Can I remove silicone from a part of the aquarium instead removing from the whole and apply new silicone? Also can I apply second coat of silicone over the old silicone layer which I have applied 1 week ago?

Thank you,


Partha Chakraborty on September 02, 2017:

Hi, you have mentioned under "A common misconception":

A common misconception.........silicone sealant needs to be removed from between the glass panes. This is not necessary and strongly discouraged. Only loose pieces of silicone between the glass should be removed if they exist. Most of the time the silicone bond will still be intact between the glass panes. The silicone that needs to be removed is on the inside of the aquarium. Again you have mentioned under "Removing Old Silicone" Keep working until there is no more silicone residue. This is very important as new silicone will NOT bond to old cured silicone.!!!!

Marion on February 16, 2015:

I just removed my masking from the sides after a few hours drying and it pulled the silicon with it! Went over the areas it pulled away from with more silicon in a panick! Help!

Lupe on September 07, 2014:

I found an old fish tank that was gently used in my attic and I wanted to use it. But I noticed that the glass has kind of a layer of what looks like smudges or a white stains that don't come off, it doesn't look like scratches but it refuses to come off with just water. What can I use to remove the smudges and bring back that clear polished look?

Nolapete (author) from New Orleans, LA on January 04, 2014:

A non gel type toothpaste and a cotton ball rubbed in circular motions will help with minor scratches. Deeper scratches would likely require a jeweler's cloth and whatever they use to polish with. Only the toothpaste method is safe to use inside the tank.

Nolapete (author) from New Orleans, LA on June 07, 2012:

As long as the silicone wasn't cured, you should be fine. Curing takes at least 24 hours. The only thing about going over it twice is that when it does cure it probably won't look very nice.

Amar Salvi from India on January 20, 2012:

Goodstuff,mate! Really insightful.Didn't know about using distilled white vinegar.Thanks for sharing.

RichardCMckeown on August 31, 2011:

Amazing... thanks for the tips.

See more: How To Wire A Range For 3 Wire Cooktop To 4 Wire Supply, How To Wire A Range For 3

destiny357 on December 01, 2010:

Wendy Henderson from Cape Coral on December 01, 2010:

Very good information. :)

awesome77 on December 01, 2010:

I am new also, and the score ratio is baffling! Just keep writing and see what happens! Now i just write to make sure i make some money and give my readers some useful info. Great hub in my book!

seanorjohn on December 01, 2010:

Don't worry about the score it will def go up. Voted up and useful. This might help with the score.