Well i know the only aqurium silicon i can find around here is only rated for 30 gal tanks. So if your sealing the bottom of your tank it might not be able to stand the water pressure. I just resealed a trashed 30 gal and 55 gal this summer. Both i found on garbage day. The 30 needed all the seams redone. And it took me a few tries to get it right, because the bottom of the tank leaked when the tank was all the way full, but not when it was half full. (water pressure) the 55 was only cracked in the top 3 inches so it stuck and no very much water pressure. I would check your silicon tube to see how big of tank you can seal.
BTW Welcome to your fish tank.
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