Most of us keep the CO2 tank under our aquarium, with no more than 3-4 feet of tubing involved. For that situation it doesn't make a lot of difference which type of tubing you use, as far as I can see. But, 20 feet is a lot of tubing, with a lot of surface area to lose CO2 thru. For that situation I think you need a good quality CO2 proof tubing, and definitely not silicone tubing.