Improvements on DIY CO2, or How I got 20 ppm in a 100 gallon on yeast and sugar
This is my first post here, and I make it because I feel compelled to share with you my good fortune in re-engineering the diy co2 yeast and sugar method. Maybe re-engineer is too strong a word, however I did modify the method to some measure of success.
Let's get down to brass tacks then, shall we?
First, the method is scalable. This means if you get a certain rate of co2 production out of 2 liters, then, everything else being equal, you will get twice as much out of 4 liters. So I modified a 5 liter plastic jug, which didn't have a secure cap, to fit a 2 liter bottle cap, to which I air-tightly fixed aquarium tubing. Do this any way you deem feasible, but just remember production can be increased to any practical size the situation demands or allows. In my situation, for 100 gallons, 5 liters was sufficient.
Now, I'm an amateur brewer and winemaker, so I know a thing or two about yeast. First thing you need to know is that there are different kinds of yeast. Winemaking yeast, which you'll either need to order online or visit a brewer's shop, is essential here because it produces CO2 more vigorously, let me rephrase, MUCH more vigorously, than breadmaking yeast. It also finishes more cleanly, so when it slows down you know it's almost dead, it won't weaken slowly over a week like bread yeast will in the alcohol it produces. Not least important is winemaking yeast's ability to live longer in higher alcohol concentrations. This is an overwhelming advantage. It means you burn almost all your sugar, so your CO2 consumption can be measured in sugar consumption! Remember, 180 grams sugar can theoretically produces 88 grams CO2. I'd safely bet you can get nearly 80. A pound of sugar can yield 200 grams of CO2 over three weeks. I'm using 2.5 pounds. You'll need a teaspoon of yeast, it multiplies quickly.
Next thing about yeast: They can't live on sugar alone. Not well enough to produce CO2 with maximum efficiency, anyway. You'll need yeast nutrient. I've used my own concoction, in which I heat-killed bread yeast in pure lemon juice, (more like pasteurizing, less like cooking) for about 15 minutes, with resulted in a creamy slurry. I froze this into ice cubes to complete the lysing process. 2 ice cubes per 5 liter, yum. Next time I'm going to try fish food, seriously. All you need is protein, vitamin c, and potassium and phosphates. Yeast need it to grow and reproduce and metabolize strongly. Fish food might be the ticket, considering I'm not going to drink the stuff. 2 tablespoons ought to do it, mixed thoroughly in solution..
2.5 pounds of sugar, already mentioned that. Fill to below the neck with lukewarm water, give some room for foaming.
Put your rig into a stable bowl or basin of water, with water up to 2 or 3 inches up the side of the jug. put a small 50 watt aquarium heater into the water where you can fit it. If you can't fit it, you need a bigger bowl or basin. Keep it around 30 degrees centigrade, or about 85 F. Wine yeast takes some time to get started , so you may have to wait 12 hours or longer to see any action. You can add more wine yeast and speed things up some, but only if you're desperate. It seems a waste otherwise. During this time, you can check your setup for air-tightness, because it won't be producing much CO2 at this time. You know when it's started., and you'll see crazy bubble counts starting soon after, during the next day.
I feed mine into an auxilliary output on a filter powerhead, which does a great job in atomizing the CO2. I get a healthy spritz every 1 to 3 seconds, saturating the tank in a CO2 mist. I can expect this rate for 15 to 20 days, after which I'll need to change my solution. In all honesty, I haven't checked my KH, but my pH was 7.2 before dosing and now it's 6.5. That's with an out-gassing overhead biofilter. If that's not 20 ppm, it's in the neighborhood. Bubble count is off the charts, at least 80 bpm. They come out in clusters so it's difficult to be completely accurate.
You may want to turn off the heater when the lights are off to prevent overgassing. If you wish to slow down or cut off the CO2 supply, do not do it with a valve, as the pressure could cause a rupture or an explosion, hardly dangerous but messy and counterproductive in any case.
This is a continuing voyage. Next stop: Lighting upgrade.