# 20 year old silicone, does age matter?



## Daniel12490 (Jul 30, 2014)

Hi Everyone,

I have just begun leak testing my used 180 gallon tank. If you have seen my previous threads I had quite a tough time with removing the bulkheads. However, that is all squared away now. So far so good, no leaks coming from the bulkheads. However, the tank is an All Glass Aquarium built in 1996. Should I be concerned about the age of the silicone? If all goes well and I have no leaks will it service me for another 10+ years or should I reseal the tank before bringing it into the home office?


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## DaveK (Jul 10, 2010)

The tank should work fine. Plenty of people have tanks that are over 30 years old without a problem. However, you might want to reseal the inside edges for peace of mind.


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## Izzy- (Jun 11, 2014)

According to Joey aka The King of DIY you should reseal your aquarium every 10 years to keep it in tip top shape. I'm sure it'll be fine, but why not reseal it anyways just to be safe? Better now that it's empty. But that's just my opinion.


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## Daniel12490 (Jul 30, 2014)

The tank is 180 gallons with two overflow boxes. What brand of silicone do you recommend? 



Izzy- said:


> According to Joey aka The King of DIY you should reseal your aquarium every 10 years to keep it in tip top shape. I'm sure it'll be fine, but why not reseal it anyways just to be safe? Better now that it's empty. But that's just my opinion.


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## Nlewis (Dec 1, 2015)

Daniel12490 said:


> The tank is 180 gallons with two overflow boxes. What brand of silicone do you recommend?


I've used GE silicone 1 for window and doors. I've used it to reseal 4 tanks with no issues. You have to make sure you get the silicone 1 though as most of the other ones have an anti mold agent in them.


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## Olskule (Jan 28, 2010)

Nlewis said:


> I've used GE silicone 1 for window and doors. I've used it to reseal 4 tanks with no issues. You have to make sure you get the silicone 1 though as most of the other ones have an anti mold agent in them.


I second the GE Silicone 1. I've used it for years to both repair tanks and to build tanks from scratch. That said, I do know that the tubes of it sold now do not say that it is safe for aquariums, although it used to say specifically that it was safe. I don't know if they changed the formula or they just sell their silicone to other companies that market it specifically for aquariums and jack the price up, and GE simply doesn't want to compete with their volume clients.

Maybe Joey, the "King of DIY" knows something I don't, but as far as resealing the tank, from my experience it has always seemed that if a tank isn't leaking, the original bond at the seams is stronger than if you try to clean the old silicone off the glass and put new silicone on it, because it is extremely difficult to get absolutely all of the old silicone off the glass (especially off the cut surface) and new silicone doesn't seem to bond well to already cured (old) silicone. Also, I may be wrong, but I have always been under the impression that silicone, once cured, is inert, so it shouldn't age or break down. I have been using some of the same aquariums for decades and the only time I have ever known of a seam to start leaking is if the tank is under stress from being filled up on an uneven surface or a new tank has a manufacturing flaw, such as the glass not being perfectly clean when the tank was made, and the silicone couldn't bond well to it.

Personally, if it was me, and the tank shows no sign of having been repaired before, I would just concentrate on making sure it was set up on a perfectly flat and stable foundation and trust the original silicone, but we're talking about a LOT of water, so you do what you think is best. Good luck!

Olskule


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## Virc003 (Dec 3, 2011)

Has the tank ever sat dry in a non-climate controlled environment? If it has had water in it for all of the last 20 years, then I would trust it. If you just pulled it down from the attick, then you need to reseal it. Once the silicone starts to dry out it will lose its flexibility and start to leak.


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## burr740 (Feb 19, 2014)

If it aint broke dont fix it


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## Nordic (Nov 11, 2003)

A leak is such a pain in the butt and never convenient.
Resealing is easy, quick, and worth the peace of mind.


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## Daniel12490 (Jul 30, 2014)

The tank has sat dry for over two years in a warehouse. Not sure how well their AC and heating was in the building. For those two years the tank sat on its wooden stand. At the moment it is in my garage holding water asides from the leaking bottom bulkheads. I am assuming once I fix the bulkheads I'll refill the tank and let it sit for about a month, if no leaks I should be good? I am tore between just resealing and starting with fresh silicone or the old saying if it ain't broke don't touch it. Additionally, does GE sell any black silicone? I had a deep blue tank and they have black silicone and gives it a nicer look. 

Thank you everyone for the responses thus far!


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## Seattle_Aquarist (Jun 15, 2008)

Daniel12490 said:


> Hi Everyone,
> 
> I have just begun leak testing my used 180 gallon tank. If you have seen my previous threads I had quite a tough time with removing the bulkheads. However, that is all squared away now. So far so good, no leaks coming from the bulkheads. However, the tank is an All Glass Aquarium built in 1996. Should I be concerned about the age of the silicone? If all goes well and I have no leaks will it service me for another 10+ years or should I reseal the tank before bringing it into the home office?


Hi Daniel12490,

I had a 45 gallon tank 1983 All-Glass tank that did fine for a couple of years until a bottom seam let go......it is amazing how far 45 gallons of water can spread out even in a carpet. I wonder how far 180 gallons can spread out?


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## Daniel12490 (Jul 30, 2014)

One can safely assume from this post that it is resealing time lol. Any tips?





Seattle_Aquarist said:


> Hi Daniel12490,
> 
> I had a 45 gallon tank 1983 All-Glass tank that did fine for a couple of years until a bottom seam let go......it is amazing how far 45 gallons of water can spread out even in a carpet. I wonder how far 180 gallons can spread out?


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## Seattle_Aquarist (Jun 15, 2008)

Hi Daniel12490,

One can assume that....lol

For a sealant you have a lot of choices but you want 100% silicone sealant without additives for mold, etc. All-Glass is now Aqueon and they have a sealant (expensive), there is also a Marineland brand, DAP General Purpose 100% Silicone...whatever you chose buy it in the 10.3 oz tube and use a caulking gun (you may need a couple/three tubes).

The key to success is preparation. Removing all of the old silicone, thoroughly cleaning away all residue and any solvent residue from cleaning, and a dry surface. There are a bunch of threads on the internet on how to do this....read several. To be truthful I did a reseal and the first time I wasn't through and it leaked (slowly). So I stripped out all the silicone, cleaned, and did it again, it failed after about 6 months. I have sealed several smaller size aquariums in the past with not issues, but I think as the aquarium volume increase so does the pressure on the seals and if it isn't right it leaks. I now have a new 45 gallon and sold the old one on Craigslist as a critter cage.


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## Nordic (Nov 11, 2003)

Buy a silicone spreader, its a little tool with 4 different sized balls. You use it to shape the silicone, instead of trying to use your finger to smooth things out. Using the largest ball will leave the strongest seal,Mask well before the time, and strip the mask off before the silicone sets. Have an open pack of baby wipes ready to clean your hands with. I swear I can get things cleaner with baby wipes than with sugar soap, yet people use it on baby bums.


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## sadchevy (Jun 15, 2013)

Do Not Use GE silicone I to assemble a 180g tank. GE I is a sealant, fine for touching up the corners as long as the glass bond is good. Look for something labeled as an adhesive. There are several types out there that are a lot stronger than GE I. Try to find RTV 108 or similar.


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## Nlewis (Dec 1, 2015)

Daniel12490 said:


> One can safely assume from this post that it is resealing time lol. Any tips?


Rubbing alcohol works well for cleaning up the corners of all the small pieces of silicone after you take the razor to it. I find it a lot easier if there is someone who can give you a hand in doing minor task while you are reasealing. There are YouTube videos you can watch and recommend you do so.


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## Virc003 (Dec 3, 2011)

I tried to use a 30 year old tank that was stored in an attick and then shed for at least a decade in temps reaching 100+ deg. f regularly. The seal went the first time on the bottom after year 2 of being set up. I resealed the bottom then another leak after another year or two half way up the side. 

Tips:
Buy lots of razor blades, paper towels, and acetone(for glass tanks only; acetone melts plastic/acrylic).
Learn to push the bead, not pull it (gets in the corners better).
Apply a smaller bead than you think you will need.
If you want to completely tear the tank into seperate panes of glass then use the tank to make a jig before taking it apart.
Set up a well ventillated and comfortable area to work in.
Start with the base for practice since this will be covered by the substrate later on.


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## Nordic (Nov 11, 2003)

You HAVE to remove all the visible silicone. (not the bits that hold the glass together, the visible exposed silicone inside the tank).
New silicone does not adhere to old.


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## gmh (Jul 16, 2014)

Is there a trick to removing the old silicone? Is acetone the best way to prep it for removal?


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## Nlewis (Dec 1, 2015)

gmh said:


> Is there a trick to removing the old silicone? Is acetone the best way to prep it for removal?


Razor blades and elbow grease.


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## Olskule (Jan 28, 2010)

All of the above suggestions are good ones; the very most important one is to MAKE SURE THE GLASS IS PERFECTLY CLEAN! If you're going to "reseal" the tank, go ahead and completely rebuild it. The strength of a tank made with silicon isn't in all the silicon you see in the corners, it is mostly in the bond between the panes of glass. I have seen tanks, some of 45+ gallons, that only have silicon between the glass, not on both sides of the corners, like is most common. Personally, I feel more comfortable with a little extra silicon "frame", but that's probably just a psychological comfort, because once the bond between the glass let's go, all that extra silicon you see will just stretch and tear...and very quickly on a big tank.

For a neat, professional look, be sure to mask the corners/seams about 3/8 to 1/2 inch from the seams before assembling the tank, being sure to add the thickness of the glass to your measurements. And as has been stated above, remove the masking as soon as you can for a cleaner look; silicon that has "skinned over" will pull, stretch and give you little "Hershey's Kisses" loops that you will desperately want to smooth over with your finger. DON'T! You can cut it off with a razorblade after it cures and never notice it. And pull the tape back against itself for a cleaner effect, and not straight up, perpendicular to the glass.

Also, look at the tank before you tear it apart and make yourself comfortable with which panels are sealed on their cut edge and which ones are sealed to their inside surface. (In other words, which panels "butt up" against other panels.) While silicon is curing is no time to stop and think about which panel goes which way. And don't worry when (not "if") you get silicon all over the tank and yourself; as long as you have taped off your corners, anything that gets on the faces of the glass can be scraped off and cleaned later.

That's pretty much all I can remember from working with the sticky mess, but once you've built your tank, whether you actually cut the glass yourself or not, you will feel a bigger sense of pride in it. Good luck!

Olskule


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## GraphicGr8s (Apr 4, 2011)

sadchevy said:


> Do Not Use GE silicone I to assemble a 180g tank. GE I is a sealant, fine for touching up the corners as long as the glass bond is good. Look for something labeled as an adhesive. There are several types out there that are a lot stronger than GE I. Try to find RTV 108 or similar.


And that is the best advice. I use DC 795 (black) It is what Disney uses to build their (large) tanks. 

Personally I wouldn't mess with the structural silicone of the 180. Just clean, reseal and leave the original bond intact.


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## Olskule (Jan 28, 2010)

Someone mentioned above that aquariums that have been stored for a long time tend to be more prone to leaking, and after thinking about it, that seems reasonable, although I'm not sure I agree that silicon "dries out". Though I have never had a problem with some very old tanks, I have also never dealt with tanks that have been stored for long periods of time, either. However, I do know that any dissimilar materials that are presumably "bonded" to each other have different rates of expansion and contraction, so after many repeated temperature changes, like you find in warehouses and storage places, I imagine the bond between the silicon and the glass has separated somewhat on a microscopic level, so I think I would go with the "better safe than sorry" school of thought on this one; a 180 gallon tank holds a LOT of pressure. Just picture it in your head, 180 gallons of water spread out everywhere. Not a pleasant thought.

Olskule


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## Nordic (Nov 11, 2003)

Just go throw 2 gallons of water on the carpet to get an idea.


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