I had to go see what the Nutrafin system was. I think its not building up enough constant pressure to allow a nice steady stream of co2. It comes out in burst cause when it builds pressure is releases then had to build up again every 42sec. I think you pay for what you get. Better invest in a pressurized tank. You can get small 9oz paintball tanks with simple regulator won't cost you that much to setup.
Problem is can I get a pressurised system for a 20 gallon tank? I do know these are loads better and would have got one instead of this crap Nutrafin one but i've heard using pressured Co2 isn't healthy for a tank 20 or under gallons.