In this post, I thought I would tackle a different subject than I have of late, as most of my posts have been dealing with the plethora of lighting questions my clients have had, especially pertaining to LED light use.

This time I will talk briefly about aquarium silicone, as a client recently asked me about which one to purchase and she told me that she was rather confused when searching on Google.
So I searched Google for “Aquarium Silicone” and was not impressed with what they served up, which seems to be the case with most Google searches that are more a search for Amazon, eHow and other often poor quality information websites.

Anyway, enough of the commentary about Google.
As many websites do get correct, that you need to use 100% PURE silicone Sealant, NOT a silicone with mold inhibitors or similar.
What most of these websites do NOT get correct is that you also should use one that is certified pure for use around containers used for human consumption.

Why is this important??
For one, your food is often only briefly exposed to this silicone, YET your fish are constantly in water that is in contact with the silicone.
Why would you expose your prize fish friends to a silicone that cannot even meet the USDA, Agricultre Canada, and FDA regulations?

The answer is obvious and the only ones that state this is Dow Corning (sold as Aqueon in the Aquarium Hobby) and the American Aquarium Products Brand (which is my preference based on quality AND Price).
I have not found these at Home Depot and other sources, not to say these do not exist, but I would not risk the purchase of your silicone at a home improvement store, even though it might say 100% silicone, these silicone may have additives if you do not look closely and even more likely is these will not be approved for use around human food preparation.

Once you have obtained the correct silicone you need to removed all old silicone and dry the surface thoroughly, and make sure no oils are present before re-applying new silicone.

When you apply the silicone using as caulking gun, I recommend a .5cm (or smaller) bead in the inside edges. Then use your index finger to smooth all inside edge beads into a smooth surface, quickly wiping away excess silicone.

Tighten all outside corners with strong reinforced duct tape. For tanks over 75 gallons I recommend wooden clamps.

Allow 24 hours to dry for minor repairs and 48 hours to dry for major repairs, such as an entire seam top to bottom or the entire tank.

Should you need to replace a glass pane, or for a DIY aquarium build refer to the picture below for correct glass thickness:

Also while many aquariums are now built with tempered glass to save on costs, this is NOT you best choice, as Float Glass is the better choice since it is more flexible and less brittle than tempered glass.

The website below has excellent information about the use of aquarium silicone, proper application and resource links for purchase CORRECT Silicones for aquariums too.
As well I should note that I have used some of the content including pictures with permission from this website:

Aquarium Silicone, Tank Repair, Applications, DIY, How To Use