Will any silicone work in my tank??

[Airbrusher]

Can I use any silicone in my tanks as long as they are labled (100% silicone) or do I need to use a brand thats made for aquariums only?

[mewickham]

The ones labeled 100% silicone are supposed to be safe. Definitely do not buy any labeled as Tub and Tile or similar. They contain arsenic as a mildew control and are toxic to fish.

[Airbrusher]

Ok....I was at Walmart the other day and they had the large caulking style tubes that were labeled "100%".....I have a 10 gal with a crack in the glass i'd like to patch up for an extra planted tank, plus my main tank is an old Oceanic tank and the silicone is all ragged looking....like maybe a pleco chewed on it or something....lol. I'd like to cut all that old silicone out and replace it with new and I just wanted to make sure it was ok to use silicone from Walmart or should look for something better?

[dennysfishroom]

On one of the forums, I resd that 100% silicone labeled "Silicone I" was acceptable for aquarium use. Can vouch from personal experience, but that's what they said. Denny

[sumpnfishy]

Silicon I and Silicone II are both safe if you get the clear ones made for windows. The silicone I is stronger but has a MUCH stronger smell so it is better used with good ventilation. For building tanks or sealing corners it would probably be better. Silicone II is fined for small patches or to cover a crack (when you need sealant but not support) and is good for securing things inside the aquarium.

[mewickham]

I am not familiar with either Silicone I or Silicone II, but I have this recollection that someone on the Aquarium Hobby Historical Society mailing list recently lamented having poisoned a tank with Silicone II. Unfortunately, I could not find the message. Perhaps Corey will remember it. I did however find this and other negative references for Silicone II in a Google search:

http://www.aquariumadvice.com/forums/f20/ge-silicone-i-diy-cave-101060.html:

GE Silicon I is safe, GE Silicon II will poison the tank. The type II contains an anti-mildew agent that can leech into the water. Regardless of type, let it stand for at least 48 hours before getting it wet so it has time to cure.

[sumpnfishy]

They had to have used one designed for tubs. Both 1 and 2 have different versions. I've used Silicon II to make my sponge filters for about six years with no ill effects even when they were placed in the tank only a week after I made them.

[aulonocaraaddict]

With the taking out of the old silicone they suggest removing it all then using a solvent to clean the glass and let it dry completely before adding the new silicone. From what I have read the new silicone won't stick to the old silicone. GE 1 is what I have heard is best to use. I know lowes/home depot sells aquarium silicone if you want to go on the cautious side.

[sumpnfishy]

From Cichlid Forum regarding I vs. II (this is from a guy who does a LOT of DIY)
Silicone I gives off acetic acid while curing. This is the vinegar smell. A friend of mine worked in Axelrod's aquarium building company many years ago and still has problems from the damage it did to his sinuses and lungs. Your body gives you no warning of the dangers of breathing in acid vapor. The hazard of smelling this stuff prompted the development of Silicone II which instead gives off ammonia. Your body knows about ammonia. II has about 80% of the strength of the original formulation, plenty for building a tank. Once the II is completely cured, it no longer gives off ammonia, but until then it is not safe with fish. If you do all your assembly and curing in a separate place from your fish, there should be no problem. However the company is off the hook with their disclaimer. I always use the original stuff but make sure have ventilation in the area, and a fan blowing fresh air right at my work site.