i used Cyanoacrylate adhesive ( some stores know it as 1-2-3 adhesive cuz it will dry and solid in 3 secs ) in my tank before no toxic at all , just wash it after it dried to wash away remainin sprays ...
I am not so sure if silicone will do the thing, depends where the wood has been broken. you get a tipe of nutraul glue at any woodwork shop that is the best to use, and does not have any cemicals in..