CO2 ingredients.
2 liter bottle.
Fill the bottle with lukewarm water 2 inches from the top.
pour it into a bucket.
add 2 cups of sugar, and dissolve it.
and 1/4th teaspoon baking yeast. Make sure the temp is within a few degrees of 100 degrees before adding yeast then stir it until it dissolves.
Then pour it back into the bottle up to about an inch away from the bottom of the cap.
Drill a whole into the cap and insert the tubing. I would use a ladder diffuser on the end of the line. (look it up) around $10.
Then wait about 2 days and it should be pumping out like crazy. You don't need a bubble counter although if you do make one (pm me for instructions) it will prevent the small amount of yeast from getting into your tank.
I can send you a video on making this because I am making a new batch hopefully tomorrow. The two liter will last you about a month. It's cheap and works (perfect combo).
I hope this solves your problem Pm me with questions, I haven't figured out how to follow a thread, or start one for that matter.
Enjoy!
Maybe a check valve if you want... I don't