Silicone bottom of tank?

[neoh74]

So I purchased my half round 118 gallon glass aquarium where the scum obviously hid the crack on purpose, or at least tried to keep it from leaking himself but couldnt and didn't tell me about it. I have my new glass bottom coming in a week or so andreally like the idea of the black bottom silicone \. I will have a sand bed, and the new glass will be tempered after the bulkheads are drilled, but I see the thin layer of silicone as an extra layer of protection from rock falls or leaks. Does anyone have experience with this? Should i seal the tank first, let cure, then silicone the rest or seal and silicone the whole bottom at one? Or not at all? Obviously silicone up to the overflow and not around the bulkheads...

[pfan151]

You’ll have to disassemble the entire tank and redo all of the silicone. There’s nothing wrong with adding a layer of silicone along the whole bottom if you want to but I’d definitely do the actual sealing first. I don’t think you should spread silicone along the whole bottom though. It’s very unlikely the glass will ever crack from dropping something on it.

[Wonton Soup]

Once silicon has cured, new silicon added to it will not cure together. So, as pfan151 said, you have to completely disassemble the tank, scrape it, clean it, and rebuild it all in one go.
If you just try to change the bottom, the tank will not have the structural integrity needed to hold full of water.

[candymancan]

Originally Posted by Wonton Soup

Once silicon has cured, new silicon added to it will not cure together. So, as pfan151 said, you have to completely disassemble the tank, scrape it, clean it, and rebuild it all in one go.
If you just try to change the bottom, the tank will not have the structural integrity needed to hold full of water.

Wrong.. old wives tail from 40-50 years ago.. Silicone today is different then back then so when you hear stories like this its from older people spreading miss information.. New silicone does infact stick to old silicone. Its been proven over and over again, look it up.. I tested this myself as well.

Dont believe me ? Grab some GE2 silicone from the hardware store.. and glue some to your dry upper silicone on your glass tank, the silicone on the top corners so it wont show,, Let it cure. 100% garuntee you wont be able to pull that silicone off the old stuff. Or get a test sheet.. put some silicone beads down.. let it cure, put new silicone on top.. let it cure.. you wont be able to pull it apart

Anyway, if you plan to re-seal the tank, you should do the whole thing not just one section

[neoh74]

My tank is a half circle, I took off the bottom glass that was cracked, so pretty much disassembled. I am going to trim off seal fro back wall but leave the glue piece in, clean then reseal the entire tank when my glass comes in in a week.


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[neoh74]

After some finagling I got my replacement glass from Peninsula Glass in Washington. Great prices and shipping. I opted to have the overflow holes prescribed and the glass tempered. Got it in this weekend and opted to silicone the bottom while I resealed the entire tank. To compensate for an even gap around the glass I flipped the tank on its side and inserted rubber X’s for tile setting on the back wall then used strips of packaging tape to secure the glass in place. I then flipped the tank back up and resealed the whole thing. The tape on the bottom helps to not create a mess. Been 3 days, gonna take off the tape on day 6 and make sure the bottom is completely sealed then wait 3 more days to water test. Can’t wait to get my tank back up!


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[pfan151]

What did you use for spacers to keep the weight of the tank from pressing all of the silicone out along the bottom?

[neoh74]

This tank assembly is weird. The bottom piece goes inside the circle, the tank doesn’t rest on the bottom glass. So when I used the spacers it gave me an even 1/8 inch around the entire bottom which I used clear packaging tape to hold in place while I flipped the tank back upright.


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[neoh74]

Couple hours in, 1/3 full...so far so good

[pfan151]

Looking good. You’re brave doing the test fill inside your house

[neoh74]

The glass piece I replaced was the bottom, and it fit inside the back and round side panel. I pulled off the seal from the back panel but left the glue in place and resealed the whole tank. With the amount of pressure on the bottom and nothing really to blow out I figured what the heck. Very little chance of a blowout. Only leak I had was a little weep into the overflow. About a teaspoon overnight, not a big deal. Of course I just went a little a time and verified every couple hours there were no leaks before adding more water. It’s raining this weekend, if I wanted to leak test pretty much had no other choice.


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[neoh74]

Update love watching it clear up.


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[neoh74]

And final. Long time but worked on it one piece at a time...


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