toxic silicone

Question
i just got a 50 gallon aquarium from my neighbor. it had a very small hole in it so we put some silicone on the outside. will that be toxic to my fish. and i noticed that someone before me put some silicone in it and i dont know if it is toxic or not but it has been in there for a long time and cured. so can i  put fish in there or will they die.

Answer
Hi Nikki,

Silicone will not be toxic to your fish. Silicone is used in various brands of aquarium sealant. Check the bottle of silicone, and see if it was designed for aquarium use. If it was, then it's obviously non-toxic.

If your silicone was just household maintenance/repair silicone for glass windows, etc, check to see if the label says "Mildew Resistant". Certain types of mildew resistant silicone may be toxic to your fish. Any silicone without the mildew resistant attribute will NOT be toxic.

If you are unsure, just soak the aquarium in water for a week or two. Chances are, any harmful chemicals will leach from the silicone and into the water. Then, change the water.

If someone had used silicone before, and you've put fish in it previously, it's definitely non-toxic.

Good luck, and happy fishkeeping!