I have used silicone I in the past without the bioseal to reseal a 55. I tried tracking it down again this past week without any luck, as I found silicone I, but this time they didnt have the kind without bioseal... if you go this route, just make sure there are no mold or mildew prohibitors in it. I believe it is just a liability thing, as I'm a member of other forums, of which I have read people using Silicone I to build tanks in the hundreds of gallons, with no problems.