Hey! good question I am re-siliconing or re-caulking whatever you want to call it a used 30gal I got. This tank was mad nasty I was going to do a whole article about refurbishing it but I am impatient so I have just been working hard with it. After I cleaned it with all natural cleaning products which SHaklee products work great for. I then took a razor blade and scraped off all the old bad silicone. Now my 30gal held water too, I STILL recommend taking that silicone off before re-siliconing, otherwise you are going to have a mess of water on your floor. It may hold now, but trust me, take it off clean the tank again after and then re-silicone it. Also make sure that you leave that stuff sit for a while to make sure it is nice and set. That is another huge mistake I have seen people make, it's bad news. Any other questions?