# Putting new silicone in an old tank



## cthulhu.meets.world (Apr 27, 2016)

I thought I'd just make a separate topic to ask this. My used 120 gallon tank has some corners that look like they need to be resiliconed. Most of the silicone looks like it's in fine shape. Can I just do these trouble areas or do I have to redo the entire thing? Everything on the outside looks to be intact, I'm just worried about the inner seal in the bottom corners.


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## New2Cichs (Apr 2, 2016)

I'm far from a pro, but I watched a ton of youtube videos and just resealed my tank. I would recommend doing the whole thing. Silicone doesn't stick to silicone for some reason, so you might not get a watertight seal


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## somebody (May 13, 2014)

+1 with new2cichs. I re-sillyconed my 125 in about an hour. Even though the tank didnt need it I still did it. that's with the added step of masking tape 1/2 inch from the corners. A little work for peace of mind. Scrape the corners and be careful not to get in between the panes.


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## BillD (May 17, 2005)

I would never risk putting new silicone over old. It isn't that silicone won't stick to silicone, but rather there is usually dirt and such that is on the surface of the old that prevents adhesion. Far better to take the time to remove the old and redo completely. Having said that, if the tank was well built, without any voids in the butt joints, it won't leak even without the inner fillet bead. It is basically there as insurance against leakage, and adds very little to the structural integrity of the tank. If you look around you will find many tanks being sold, especially those made of low iron glass, that have no inner sealing fillet bead.


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## cthulhu.meets.world (Apr 27, 2016)

Alright, sorry for the delay but I have an update!

I went with your advice guys and scraped all the silicone out of the tank. It took a while because I was very tedious and also used the opportunity to scrape away all the yuck from the walls of the tank. It's so massive though! I'm not used to having to practically climb inside a tank to work on it! But I managed to get it cleaned out and taped down all the edges to apply silicone:









The next problem I ran into was my inexperience working with silicone. I thought that I could do an entire side before I went back to smooth out the silicone and by the time I tried to smooth it, the gel was already setting and the result was a bit of an ugly, lumpy mess on the right side of the tank. I was really torn over whether to strip the whole thing down and start over or push on but patience is not my greatest virtue and I decided since that corner would only be seen from the angle of my bed and most of the mess hidden beneath the gravel, I could live with my less than professional application and moved to the other side. Things went a lot more smoothly on the left side of the tank and I peeled the tape away before the silicone could set on it(I did have to use my razor blade a few times to cut clingy pieces of silicone away from the tape rather than risk pulling it loose from the glass) and before I knew it I was done!









I know, I know, the right side is bad but like I said, the worst of it is hidden under the gravel. Next came the tedious process of filling the tank. I must have checked over the silicone a hundred times, evaluating every little nook and cranny to make sure I had everything properly covered. Finally, I ran the hose in and started to fill!









I let the tank sit about three quarters of the way full for a day and there was no sign of any leaks so I set it up! I underestimated how tall the tank was though and ended up having to get on a stool so I could properly plant it. Check out the before and after pictures!

What I got:









What I turned it into:


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