I don't think GE makes "Sillicon I" in black, so your choices become either Momentive 103 or Sillicon II. From what I remember, the II contained the mildew resistant additive making it unsuitable for aquariums. I only have experience with GE Sillicon I clear, which worked for my 20 gal reseal.
You might want to look into momentive 103, which, from what i understand, has greater adhesive properties than the 'regular' sealant applications for GE I & II. I don't think it is stocked by any of the big box stores. Acklands used to store it at one point under RTV103. There are few others, like Loctite superflex, but you would have to check out the MSDS, and decide if its worth the $$$ or risk.
Probably only need 1, but get 2 just to be safe. If you run out before you get it all in, you are screwed and have to start all over again. Worst case, you will have a spare tube. Always have more than you need
John the traveling supply guy has it,and cheaper than most too. Sugarglidder,is his user name, IIRC. He posts on here when he's coming, but he will ship to you if you email him. Use the email addy on his post, not PM.. he doesn't answer PMs.