Cheap co2

The easiest way I get co2 into my planted tanks is to use dirt. I put a 1-2" layer under the gravel. The soil decomposes anaerobicly and you get lots of co2 and a little h2s. The hydrogen sulfide causes the ph to drop and stay <6.0. No good for most fish. I resolved this by adding 1/2 cup marine substrate per square foot of floor space. Sprinkle it evenly over the soil then stratify your regular aquarium gravel over it. Sorry you cannot have water in your tank when you do this-new set ups only.
The idea is u don't stick your gravel vac more than a third into the gravel(upper layer only). I grow all my plants this way and it kicks @Ss. My most productive discus breed in these tanks vs sterile.
Sugar and yeast work well I've done it; only it gets old dumping out the nasties in your yeast bottle. I got nothing against reg co2 injection just the gear can be cost prohibitive. Anyone can afford a bag of soil and a couple cups of marine substrate. Try it u will be converted to the dirty side...
-lilydog aka rob

Thanks for the tip!