Can I put more silicone over new (but dried) silicone when sealing glass aquarium?

That Reefer Man · Mar 30, 2017

So i have a 100 gallon tank that started to slowly leak from the bottom last week. The silicone throughout the tank was 10+ years old and was practically flaking off so i decided to redo the whole tank.

I put everything into another smaller tank, drained it, dried it out, then cleaned all the old silicone off. Once that chore was done, i applied a few tubes of new aquarium-safe silicone. Well after 4 days its leaking again from the same bottom seal.

So my idea now is to just add more silicone over the new silicone i added a few days ago, will this work? having to get all that silicone off again would be a real pain. any other advice? it seems like the weight of the decorations pushed down enough on the bottom glass to separate the seam along where the bottom connects to the vertical glass. i watched a bunch of youtube videos on how to do this but obviously i failed

thanks everyone <3

bif24701 · Mar 30, 2017

That Reefer Man said:
So i have a 100 gallon tank that started to slowly leak from the bottom last week. The silicone throughout the tank was 10+ years old and was practically flaking off so i decided to redo the whole tank.

I put everything into another smaller tank, drained it, dried it out, then cleaned all the old silicone off. Once that chore was done, i applied a few tubes of new aquarium-safe silicone. Well after 4 days its leaking again from the same bottom seal.

So my idea now is to just add more silicone over the new silicone i added a few days ago, will this work? having to get all that silicone off again would be a real pain. any other advice? it seems like the weight of the decorations pushed down enough on the bottom glass to separate the seam along where the bottom connects to the vertical glass. i watched a bunch of youtube videos on how to do this but obviously i failed

thanks everyone <3

What you should do is disassemble the entire tank, remove each pane and scrape off all the old silicone and redo it all. And don't put anything in it for at least 2 weeks. Do it right and that tank can last 10+ years no problem.

That Reefer Man · Mar 30, 2017

I wish i could do that, I just dont have the space or knowledge to go that far, At this point im reading about other reinforcement options but idk

Blacktank · Mar 30, 2017

Agreed. You might get a short term fix by covering the silicone, but it will not last long if you do. I. Doing a 160 gallon now. Take it all apart and put it all back together. Use acetone to make sure you get all the old silicone off and put it back together

ahiggins · Mar 30, 2017

I was always under the impression that you cannot bond silicone to silicone...good luck though

that sucks

That Reefer Man · Mar 30, 2017

does acetone work better than 91% rubbing alcohol? i just dont think i put on enough silicone the first time, im now seeing that larger tanks need a lot more

Cment · Mar 30, 2017

I wouldn't reinforce in any way. You'll need to reseal the tank, which some times only requires scraping off the existing silicone while leaving the tank together. Could you post of pic of where the leak is coming from and the existing silicone? You don't want a temporary fix, a 100 gallons of water on your floor and dead livestock is not what you want....

Cment · Mar 30, 2017

If you don't feel comfortable resealing the tank, I would see if a local reef club member can help you or cut your losses now and purchase a new tank.

That Reefer Man · Mar 30, 2017

when i push down gently on the lower pane of glass i can see where the silicone isnt connected to the wall all along the back side
it looks like i might just take all the silicone off and re apply new and this time test it outside lol so i dont wake up at 3 am again to 100 gallons of water on the floor, luckily all my floors are tile here lol

bif24701 · Mar 30, 2017

That Reefer Man said:
when i push down gently on the lower pane of glass i can see where the silicone isnt connected to the wall all along the back side
it looks like i might just take all the silicone off and re apply new and this time test it outside lol so i dont wake up at 3 am again to 100 gallons of water on the floor, luckily all my floors are tile here lol

Once you assemble, place the panes of glass together it's really important not to allow the joints to move until its 100% cured.

That Reefer Man · Mar 30, 2017

i want to make sure i understand this correctly...the silicone in between the joints just holds it together right? its the seal that actually stops leaks? from the outside of the tank the silicone in the seams looks perfect it was just the inside seal that was falling apart before.

Blacktank · Mar 30, 2017

True, but if that silicone is light or not attached well, then it will allow the leak sooner

smokin'reefer · Mar 30, 2017

I see now you are in a much worse predicament than I am. Remind me of the saying about the guy complaining about no shoes, meetts the guy with no feet. I don't have any experience silikoni glass but I do have this 90 gallon reefer that has solid glass in it if you want to try and re silicone it. This 3/4 inch glass doesn't Flex. Haven't had a chance to take a good look at it. Just got it taken out onto the back deck yesterday.

That Reefer Man · Mar 30, 2017

im on the west coast

pickupman66 · Mar 30, 2017

Simple answer to the OP question. NO. you cannot bond fresh silicone to cured silicone. wont work.

The BEST way to fix this is to completely cut the panes apart and remove all of the silicone and then re-build the tank. However, if that is Not an option or in your wheelhouse, i have personally redone just the joints (not between edges of panes) before with good success. I rebuild a 210 that had a broken end panel. I replaced that panel completely and then redid the rest of the inside silicone. It was a chore but I got it done. Tank held water well but then I sold it because I got a 180 instead. YOu need to get all of the old silicone off. Acetone is your friend and a good fresh razor.

smokin'reefer · Mar 30, 2017

Oic. I think I confused you with Reefer Madness.

cromag27 · Mar 30, 2017

Silicone takes at least a week to fully cure, depending on bead size. the best stuff to use is momentive rtv 100 series.

don_chuwish · Mar 30, 2017

Given all the risk and what seems like low comfort level with doing it right (full disassemble, clean, rebuild) I'd say a brand new replacement tank is the way to go here. Save yourself a ton of time, effort and stress for not a lot of money. Sell this one as a terrarium on Craigslist.

scardall · Mar 30, 2017

check this link out. http://archive.constantcontact.com/fs131/1102741445137/archive/1112808580482.html and
http://www.permabond.com/2015/07/08/bonding-silicone-rubber/

Airwarf · Mar 31, 2017

That Reefer Man said:
does acetone work better than 91% rubbing alcohol? i just dont think i put on enough silicone the first time, im now seeing that larger tanks need a lot more

No Rubbing alcohol is water compared to acetone. Here is acetone vs a plastic card. You can get acetone around the paint section of your local hardware store. It's not that expensive. Use gloves or else it'll be damaging to your skin and it's very aromatic so open a window.

You can do it man. Just make sure that glass is perfectly clean, tape your seams off where you don't want silicone, and have plenty of paper towels handy. Clamp in place and let dry.