Actually the gorilla glue I mixed in coco in a pale of water, about a 1-10 glue to water ratio and it worked great...got a thick coco background thats had no problems. I use this at home.
With weldbond I usually have to patch and repatch a couple of times, but it too works well. I used this method with the class I taught and it worked good (not nearly as tough on hands if it gets on them, which with 7th-8th graders it will everytime).
Here is a link to the class (pics of the weldbond being used)
If you have used what 99% of folks seem to use it is GE brand room temperature vulcanization (RTV) silicone referred to as "condensation cure" RTV silicone. The vulcanization process does result in the off gassing of the following chemicals: acetic acid, methyl alcohol, ethyl alcohol and small amounts of ammonia. (reference here)
In addition, the Material Safety Data Sheet (MSDS) for IS808 or "aquarium sealant" says the following:
I think what you are smelling is probably the acetic acid since it looks like it won't off gas formaldehyde unless you get it to 300 degress Farenheit. The permissible exposure level (PEL) for humans set by OSHA is 10.0 ppm for Acetic Acid (CH3COOH). An MSDS for acetic acid says the following, "INHALATION:VAPOR EXTREMELY IRRITATING. MAY CAUSE DELAYED LUNG INJURY. EYES:CAUSES SEVERE BURNS. VAPORS EXTREMELY IRRITATING."
It would be really difficult to determine the parts per million left in your tank, but if subjectively it smells strongly, you might want to let it air out for a while. Unless there are some very high concentrations, I don't think it would kill the frogs out right, but it may cause them pain, irritation, and long term respiratory or eye problems. I use an acid gas respirator when working with silicone and have found that my eyes get irritated if ventilation is not adequate.
Probably too much in the weeds, but hope it helps.
Good stuff Marcos. I didn't use a mask when i did this stuff, so i know it doesnt smell good. Like a guinea pig cage with all the ammonia. It doesn't smell very strong, but you can definitely smell it when you stick your head in the tank. I'll put a fan in there and let it air out for a while.