I'm attempting to inject CO2 into my filter. I have all the correct supplies and I have already built the 2-liter with the tube. The only problem that I have run into is that the sealant that I used to keep the CO2 for just releasing into the air from the 2-liter is All Purpose Adhesive Caulk plus SILICONE. Now, I have heard that most silicone caulk contains an anti-mold chemical that can kill my fish. So i was wondering if this would be OK because it's not going IN the tank it is just sitting dry at the top of the 2-liter bottle?