Silicone Question

[SWerner13]

I picked up some silicone to do a DIY co2 project. I had some other things in mind now though, but after reading the back it says not for aquariums. Why is this? is it toxic or just not suitable to use to seal an aquarium?

[mr86mister]

It has arsenic in it which is pretty much deadly to fish and any underwater animals. Go to your lfs and they should have arsenic free Aquarium Silicone.

[Innovator]

It is becoming more difficult to find a suitable 100% silicone, at least for me. Make sure there is no 'Bio Seal' which has mold inhibitors added. If you have to, like me, purchase online.

[joy13]

GE silicone 1 has nothing in it to prevent fungus and mold. Most others you read has prevents mold and fungus. Wally world carries it, it has a blue and sliver label.

[BillD]

Be sure to get the Silicone I for Windows and Doors. The other version for Kitchens and Baths or Tub and Tile has mildewcide. Going to the LFS is not necessary for aquarium safe silicone, nor is paying the LFS price. Safe silcone is available for around $4 for a (caulking gun size) tube.

[mr86mister]

I purchased my silicone for $5 so it is not to much a difference in price.

[jim692]

If you can't find the GE 1 silicone, here's another option.
Ace - Ace Tree: Paint: Caulk & Sealants: Pure Silicone Caulk: Dap® Aquarium Silicone Sealant (00688)

[BillD]

The DAP is expensive for that small quantity ($6.99 for 82.8 ml), compared to a tube for a caulking gun (~ $4.00 for 300ml). The small tubes are perhaps more convenient for small jobs, but I usually have an unfinished tube available for those things. Silicne has a shelf life and while it may still work beyond that date if the tube is unopened, there is no gurantee. Once it has been opened, the time to use it is relatively short, even if the tube is well ealed.
I have actually used house brands for the last 15 or so years which are usually a little cheaper, and also say ideal for aquariums on the label.

[jim692]

As long as it says aquarium safe or for aquarium use you should be in the clear.
Check an online spec. sheet or technical bulletin from the manufacturer if you are unsure. Some are OK to use, but some will tell you they are not for continuous underwater use and/or can lose adhesion. Also if they contain any fungicide/etc. it will also let you know.
For example this one states that on page 2 of the technical bulletin.
http://www.dap.com/docs/tech/00000683.pdf
Also the MSDS sheet will list any exposure issues to you while using it.
http://www.dap.com/docs/msds/00000684_english.pdf

Best to check and avoid possible problems.

[BillD]

Even the ones that are aquarium safe will say not for continuous underwater use. The purpose of silicone is primarily as a caulk (what it was deigned for), not an aquarium adhesive. The fact that it glues glass together to create an aquarium, does not negate it's primary usage as a caulk. It's use as an aquarium adhesive was hit upon by a local gent who was using it in his work and thought it might work for building an aquarium. He and 2 partners went on to start the first "all glass" aquarium manufacturing company, Crystal Aquarium.
The warnings on the label to not use below the water are partly to protect the manufacturer/vendor from liability.