So I bought a cheap diy co2 kit off Amazon for about $15. It screws onto 2 2 liter soda bottles and I put citric acid in one and baking soda in the other. The recipe works fine and generated co2 which I can diffuse into my tank. The kit I purchased has a pressure gauge that is on top of the citric acid bottle and a needle valve that is on top of the baking soda bottle. The pressure reading is about 1.5 and can change, but seems to stay reasonably consistent. The problem is that the bubble count will not stick for any length of time. I can set it to one bubble per second or whatever with the needle valve, but in less than 5 minutes it has changed to one bubble every 5 seconds. Meanwhile, the pressure reading is unchanged. This happens even with fresh bottles of citric acid and baking soda. I think it's just a crappy needle valve, but I'm not sure what to do about it besides get a pressurized system (which I probably will do). I expected the cheap diy system to need frequent adjustments, but not every 5 minutes. At this point it's almost unusable. Any suggestions?