No you can not use it to glue with the water still in the tank. You can use superglue for that though, but you will have to be very fast. You can also get some 2-component playdough like glue, that is often use to glue corals to rocks.
Thanks for that info guys, but what I want to know is can I use it underwater? i.e. I want to glue something to the back of the aquarium and don't want to take out all the water. 1st I want to glue a new 3D background to the aquarium and 2nd a little pipe for the airstone?
i think pretty much any silicone is ok to use. on my old tank i got a crack in the glass one day when my sisters rats i mean kids were over. i used some red heavy duty automotive engine silicone sealer right on the tank as it was leaking and it sealed it up and no fish died. i actually kept the tank like that for about 6 months before i fixed it properly. the fish didnt care.
i figure if anything going to be bad for them, automotive silicone used on engines would be it.
At my local Menard's here in the Midwest, they carry a product made by Dap called Aquarium Sealant and it has worked fine in my aquarium. It's a little bit more expensive than the regular kind of stuff but it was worth it to me for the piece of mind that it was safe for my fish.
I was in Home Depot last night looking for some Silicone for my DIY caves and was looking at the GE II, it looks like all the GE II has anti-fungal and mildew additive. The GE I didn't.
As far as the GE goes, one of them says, "not safe for aquariums" the other says nothing about aquariums. I don't remember which is which. The one that says nothing is safe. This is how it was a year ago.
