Ok Ill help haha
-Airline Hose (Ceramic is better, plastic standard is fine)
-Check Valve (Walmart, Petco, Petsmart etc)
-2 Liter bottle (with lids)
-two 20 oz bottles (with lids)
-Air stone (wood or ceramic, standard is fine too)
-1 tbsp Yeast
-1 tbsp baking powder
-1 cup sugar
First Cut a hole into 2 liter bottle lid using knife. Make sure the hole is smaller than the circfumfrance than the airline tubing.
Cut the airline tube at an angle so its at a point. Pull the airline tube through the lid hole. If having trouble use pliers. Put lid back on bottle. Should look like this.
Cut airhose about 1 1/2 feet. Now get your 20 oz bottle and poke 2 holes in the lid. Run hose COMING from 2 liter bottle down through the lid and into the bottle closer to the bottom. On the other hole have the rest of the air hose coming OUT of the lid but keep closer to the lid. Fill up bottle about halfway with water. Heres Example
So the hose coming FROM the 2 liter is under the water and the hose coming OUT of the 20 oz is above the water.
Now after the hose coming from the second bottle, cut the airline again about 1 foot. Insert Check Valve. Make sure arrow is pointing AWAY from the bottle. Connect rest of hose
Not lets make the diffuser.
Cut your last 20 oz bottle in half or less (depending on you) and at the neck of the bottle, poke a hole completely through. Now take your sponge and cut it small enough so it can fit through drinking hole and run your airline through it with the sponge and connect your airstone.
Lets make the generator formula.
Well basically mix all the ingredients together with warm water (not too hot) in the 2 liter bottle and shake it up. I add the sugar first and mix that up first untill it looks dissolved then the baking soda and then the yeast.
Close caps on everything and wait!! The co2 will start coming out in about 40 mins- 1 hour and if your airstone is producing bubbles your did everything right!!
All around this cost me only like 10 dollars lol so its a great cheap way to grow plants
Keep your generator (2 liter bottle) either level with the tank of higher if possible. The 20 oz bottle with water in it is like a safety bubble counter thing. Sometimes the co2 isnt the cleanest and its better to have the bottle water catch the gunk rather than your tank catching it (personal experience :D )
Let me know if you have questions!!