View Full Version : Re-Caulking Recommendation Needed

01-10-2015, 03:03 PM
I have a 125 gallon tank on a stand. I am in the process of switching communities, so I have drained the tank and removed all substrate and rocks. At that point, I noticed that one edge of the caulking (1/3 to 1/2 of the narrow side of the tank) on the base of the tank's inside is damaged. By this I mean that the edges of caulking have been peeled away but the seam appears intact with a thick layer of caulking still at the junction of the two panes of glass (no leak). So, it is just the edges that spread thinly over the adjoining panes of glass that has been peeled away. Again, there is NO leak.

The question I have is whether or not I can just throw another layer of caulking (as protection) on TOP of the original caulking that remains in place at the seam. I know that caulking will not stick to itself (the old strip at the seam), but since there are two glass surfaces for it to bind to I was hoping that this might protect the remaining original seam's caulking by putting a layer on top and at the edges so that it does not continue to wear with contact (sand, rocks, plecos, etc.).

Please advise.

Here are some pictures (look at the left side of the edge from the corner to about halfway across).

01-10-2015, 03:09 PM
I am trying to post some more photos, but when I attach them they are not appearing with the submitted post. Anybody have any help with this too?

01-10-2015, 03:23 PM
Old caulking will not stick to new caulking. You will need to reseal the tank

01-10-2015, 03:32 PM
Thank you for the advice, Cliff.
That i am aware of (not sticking to caulk), however, there are two exposed glass surfaces that the caulk can bind to. I am wondering if this would be a good way to PROTECT the remaining caulking that is in the seam. To break the factory seal when the tank is not leaking seems like a poor choice to me, no?

01-10-2015, 03:51 PM
I will still get a leak in time if you try a patch job. The water will work its way to the glass were the new and old caulking meet. It would just be a matter of time

Resealing a tank is not all that hard as you are just replacing the outer seal. the below link explains how to do this


01-10-2015, 04:04 PM
This is super helpful to be discussing with somebody. Thank you again.

By "just replacing the outer seal" are you suggesting that I would only be taking off the layer of caulking that is visible inside the tank edges and not the caulking that is deep between the glass panes (that I would have to remove by sticking the blade into the seams of the glass). Isn't it necessary to replace both?

If I am only replacing the "outer layer" isnt it the same thing as what I am suggesting to do by replacing the caulking over the seam (because there is no outer caulking remaining in the damaged segment), just adjacent to that there is.

01-10-2015, 04:09 PM
No replacing the outer layer is a completely different situation

When done correctly, the outer seal of caulking will seal to both pains of glass eliminating the need for the outer seal to stick to the inner seal.

You just need to make sure you get a good amount of silicone to both pains of glass and you allow it to cure properly

Also, make sure you are using aquarium safe silicone

01-11-2015, 07:48 PM
I used GE window and door 100% silicone. Saw that people recommended it on other forums. The only thing is that it is mildew resistant, which worried me a little. But it is one that others recommended as being aquarium compatible.

I put on a very thick layer and properly laid the bead of silicone but somehow there are still multiple free floating bubbles in the seams now. None of them seem to be touching the glass (all free floating) so I think it should be OK. Would you agree?

I will leave the tank for 24 hours to cure. The outer edge is completely dry (after 20 hours) but when I press on the silicone, it feels very liquid underneath still. I should probably leave it to dry out another day, correct?

01-11-2015, 07:51 PM
Mildew resistant = chemicals = bad for fish

01-11-2015, 08:05 PM
+1 to the above

I would remove that silicone and re-do the outer seal.

DAP makes a silicone which is stated as safe for aquariums. I would suggest using that or the GE silicone in the thread I linked above (if you can still find some kicking around)