# Applying Black Silicone over Existing Clear Silicone...



## Off_register (Feb 5, 2015)

This may sound like a silly question but I was wondering what your thoughts are on this. I did some google searching as I found mixed reviews about this but that involved applying new silicone over old silicone on leaking aquariums. This will be for my brand new 33gal long Aqueon Aquarium that has not seen water yet. I am wondering will the black silicone adhere to the existing clear silicone? I'm hoping it will give the same appearance as my 75 gallon that has black silicone.


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## Steve C (Oct 9, 2011)

Silicone won't adhere very well to itself once it has cured. Plus the clear silicone is not actually 100% "clear" so it would still be visible and would not give the look you want.


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## Mcdaphnia (Dec 16, 2003)

If you remove all the old sealant you can replace it with black. However any missed traces of clear sealant will be highlighted by the black if they are coated over. As correctly pointed out by Steve C the new silicone will not stick well to the old. Clean very completely or the reseal job will be a bust.

Unless your day job is caulking windows, I always suggest practicing before using expensive silicone in your aquarium. Get some cardboard boxes about the size of your aquarium and some very cheap cartridges of ordinary caulk. Practice until you are perfect. Keep in mind the real stuff will be much smellier. Set up good ventilation while you are doing this and avoid breathing the fumes or getting them in your eyes.


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## Off_register (Feb 5, 2015)

Thank you for the quick responses everyone! I'm not sure I want to risk that procedure on this aquarium. I was hoping for the easy way out lol. I will be building an AIO aquarium and already ordered black silicone to adhere the plastic chambers so I was hoping I can "tint" the silicone on the vertical edges at the same time. I am by no means a professional caulker so practice will be needed. I think a cheap Craigslist tank can make for a perfect example to practice siliconing a tank.


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## Mcdaphnia (Dec 16, 2003)

Silicone does not stick to plastic. You can use silicone beads to hem the plastic in place, but it will not stick in place. Lexel is a product I have not tried but some aquarists report it worked for them. Gorilla glue, which comes in yellow and a new white, does work for some aquarium uses where there are dissimilar materials. Lexel is made by Sashco.


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## Narwhal72 (Sep 26, 2006)

Actually silicone will stick to plastic if the plastic is properly primed first. It's how AIO aquariums are made. The filter box is first primed before inserted and then the silicone is applied.

I wouldn't trust it as an exterior wall. But as an interior baffle it works fine.


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## Off_register (Feb 5, 2015)

McDaphnia, I know you said you haven't used it but I just looked at the Lexel and it says it is Mold and Mildew resistant. I thought that was the reason we stayed away from Silicone made for Kitchen and Bath?

Narwhal, what do you mean by prime the plastic?


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## Narwhal72 (Sep 26, 2006)

Much like how pvc primer is applied to pvc before gluing it's the same thing. The primer chemically prepares the plastic surface which opens it up to bonding more securely.

I can't go into the specifics because it is proprietary information but that is how AIO tanks are made.

Andy


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## Off_register (Feb 5, 2015)

Thanks for the info, Andy!


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