Lexel sealant is not aquarium safe

[Bullsnark]

I called SASHCO’s customer support team to get confirmation, but I wasn’t sure until today. Lexel is an excellent high quality sealant that has excellent adhesion even on wet surfaces, but according to their staff, it hasn’t been tested below the water line for more than 30 days, but more importantly, it isn’t actually silicone at all, it is rubber. It does in fact release chemicals over time and would kill aquatic life. 
they claimed that this was on the packaging, but I could not find it anywhere on the packaging, the website, or anywhere else available. I don’t know if you’ve ever tried to read a tube of clear caulking, but it’s not exactly easy. Especially when the tube itself is clear and the writing is black and you can see the writing on the opposite side at the same time. 

[lefty o]

pretty much if it isnt 100% silicone sealer, or labeled aquarium safe, its not safe for fish.

[Bullsnark]

Sometimes in the middle of nowhere, it’s either read the fine print of every tube with a magnifying glass, or hit up Amazon.. There are several that ARE aquarium safe that state “not for aquarium use” because of liability reasons however.