Gelatine CO2 recipe and recent tests - The Planted Tank Forum
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post #1 of 12 (permalink) Old 03-27-2003, 04:18 AM Thread Starter
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I'm still experimenting with gelatine in the DIY CO2 recipes (posted on the old and new Aquabotanic board).

As I was asked privately about how to do the mix, I figured I'd post it here along with my current tests and as-of-this-minute theories of what works and why. (Standard disclaimer here, use this information at your own risk! It is possible to kill your fish with DIY CO2, start with small volume bottles and small mixes first.)

I am using a version of the Knox gelatine "Knox Blox" recipe posted on the back of the box, to provide the sugar in the DIY CO2 recipes. I am using 1/2 of the gelatine in a bottle, so there is room for 4 or 5 cups of water. The Knox Blox is altered to use 3 cups of water and 2 cups of sugar substituted for the fruit juice in the recipe on the box. That means that the total mix contains 4 cups of water, 2 cups of sugar, and 4 packets of gelatine. Chill overnight either in a pan to be cut into cubes or in the bottle that you use as the generator. Allow it to come to room temp and fill with warm water, allowing 1 to 4 inches of space at the top. To that I add 1/4 teaspoon of yeast, then maybe baking soda, salt, and/or yeast nutrient. Actually the best thing to do is to add the yeast to the warm water and let it sit for a good while (10 to 30 min), then mix the rest. Sometimes I add a 1/4 teaspoon of sugar to the water too.

I've been testing gelatine with regular bread yeast, champagne yeast, and ale yeast along with various combinations of baking soda, salt, and "yeast nutrient" from the home brew store.

I've used some pretty scattershot methods and there are still many very basic combinations that I have not tried. The Hagen/Nutrafin CO2 System seems to use baking soda and something that I thought was salt, so I began there using gelatine for the sugar. Then I tested different yeasts and some yeast nutrient. As this has all taken place in my fish tanks, each test has taken about a month or sometimes less, so this is very slow. Plus, any trip out of town means no data. So, it's been slow.

I think gelatine in cubes works better than solid as it gives more surface area for reaction but the sugar is still slow to release. The protein in the gelatine is probably good for the yeast too and may even substitute for the yeast nutrient used by the brewers. The nutrient that I got has several phosphates and a lot of vitamins added.

Baking yeast (fresh or refrigerated if open) with 2 teaspoons of baking soda and 1/2 the Knox blox recipe in cubes in a 2 liter (actually 64 ounce) bottle would last about a month at a reasonable rate. Baking yeast seems to really benefit from the baking soda, I suppose the pH effect is important.

Champagne yeast with 1/2 recipe gelatine cubes, 2 teaspoons of baking soda, 1 teaspoon yeast nutrient foamed over really badly. Too much nutrient? Champagne yeast with solid gelatine was likewise not a good rate, but I didn't add any yeast nutrient, it was a bit foamy already, no need to aggravate that. Even though the bubble rate is not high, it keeps the tank pH at the usual level that I am able to reach with CO2 with my filter set-up (the HOB blows off a lot of CO2 so I can't get much lower regardless of the input.) I will open the bottle to stir it up if I have to later on.

Ale yeast with the same 1/2 recipe in solid form in the bottle performed really badly so I added yeast nutrient, it has foamed but not too bad (I left a lot of room in the top) The rate isn't improved. I'll stir that soon also to see if better contact improves the rate. There is a thick sludge of yeast stuff on the top of the gelatine, is that good or bad, I don't know.

Meanwhile, not using gelatine, a Hagen bottle with 1/4 teaspoon ale yeast, 1 teaspoon baking soda, 1/2 cup sugar and 1/4 teaspoon nutrient is doing really well. It was slow to start and the two bottles are behaving differently so I can't say that I know why just yet. One had remnants of bread yeast in it (the better one), the other had remnants of Hagen yeast in it (the lesser one). An earlier test of a Hagen bottle with bread yeast and baking soda with sugar was poor.

I had decided that the brewer's yeasts didn't like baking soda, but then this one proved me wrong. I need to start this one over and take better notes.

So, that's an update on the gelatine tests, and the non-gelatine tests, too.
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post #2 of 12 (permalink) Old 03-27-2003, 04:31 AM
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Thanks alot Anona, I'll go try it out this weekend. Where would I go to get some yeast nutrient? Brewery?


20G heavily planted tank with Eco Complete
Pressurized CO2, Eheim Ecco 2236, 1 55W and 1 36W bulb
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post #3 of 12 (permalink) Old 03-27-2003, 05:09 AM
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Wow thats a lot of post to read in the middle of the night when the brain is on idle
You have got some really great information there!
Sounds like quite the laboratory at your house.
I will keep track of your finding, since I have yet to set up my DIY co2 (shame on me).
Keep up the good work, sounds like fun.


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post #4 of 12 (permalink) Old 03-27-2003, 12:56 PM Thread Starter
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kor4ever, The yeast nutrient is from a home brew store. It was surprising how many there were, one was about 5 miles away.

There are different types of nutrients, this is called Super Ferment, 2 oz for $1.69. The local brew store had bins for several types but only stocked this. It came in a 5 gallon pail, sold by the oz. The different yeasts are bout 65 cents to $1 for 2 oz. He sells CO2 tanks and refills there so when I get my big tank and a pressure system, I'll need to know him anyhow.

Kelly, my very first attempt at CO2 was using the gelatine and it went for 52 days using a full recipe of gelatine (solid) and only baking yeast. I had to stir it up a few times, so then began cubing it, but then it won't all fit in the bottle and allow enough water to run well. So, I've been tinkering with this since December.

When I get to the end of playing around with this, I'll switch to a gallon jug and use the full amount, but first I need to change out my filtration as that is the limit on the system now I think. Now I can never get the pH below 7.6, well sometimes 7.4, and I figure it is the Pengin HOB filter. I removed the biowheel and keep the water level high but it still drives off a lot of CO2 it seems. I start at 8.2 and so 0.8 or 1.0 pH drop may be the most I can get anyways, I don't know. With less than 2 wpg, it might not be that critical anyhow. My plants bubble now at least in the top half of the tank, so I'm happy enough.

If I can get the Hagen system mix figured out to last a full month for the 10 gallon and the 20 gallon, and a good 4 to 6 week mix for the 29 gallon, well, I just may have to find something else to work on. Heck, maybe the stock market will be fun again.
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post #5 of 12 (permalink) Old 03-27-2003, 03:48 PM
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Are you using the Hagen "ramp" diffuser? I'm using it with a 2l bottle and find the bubles are to big and don't dissolve befor the end of the ramp. they lose about 3/4 of their diameter. (I like watching them slowdown :lol: ) if I use less yeast will the bubles be smaller or just slower, what if I use a 1l bottle like the Hagen canister?

I have 2 diffusers and tryed to hook them to one bottle but when the water pressure was overcome in one ramp the stress was released and the second ramp wouldn't bubble :evil:

I want to hook each ramp to it's own bottle but how do i get smaller bubbles :?:
Thanks Jeff
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post #6 of 12 (permalink) Old 03-27-2003, 04:53 PM Thread Starter
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I have Hagen ramps in the two small tanks, one with a Hagen bottle, the other with a Hagen bottle and a 2 liter feeding out below it. I have the same problem with 2 liter leaving a bubble left over at the end and I haven't figured this out, though I've looked at it for a long time! (This set up is so that I can keep the tank stable at 7.4 - 7.6 pH even while I play with varoius mixes that sometimes don't start well or die fast. More expensive fish here I don't want to hurt)

It looks to me that the Hagen ramp is sized such the the length will dissolve one bubble of "x" cubic units. If your bubble is bigger, all those extra units will be left over at the end, wasted. If you go through the volume of a sphere calculation, you'll see that if the diameter has decreased from 4 units to 3, then the volume is one half of the original. So, you're getting double bubbles and only dissolving one. (hope I did that right!)

I don't know if the line length is creating the extra large bubbles, or the air space in the big bottle, or even the flexibility of the bottle and tubing together. I suspect a slight expansion of the tubing and bottle, multiplied by the size of each, and complicated by gas compressibility. Could be simply random bubble rates. Whatever.

The Hagen ramp is simply intolerant of double bubbles. But so well designed! The Hagen bottles never make double bubbles. Short lines, firm canister, small air gap -- one or all of these reasons.

I've even taken an entire tube from a Hagen set and used that, including the end part, thinking that the restriction there might make a smaller bubble. No dice, same fat double bubbles. (I never tried sticking an even smaller restriction in the end, like a 1/16th tube but it might be worth looking at.)

It is not possible to have a short line with the 2 liter bottles unless you can hang them on or above the tank, ick, that's not gonna work. I haven't tried a firm canister, though I have a big Gatorade jug, I don't know if it will really be any different, I suspect the line length and gas compressibility is still involved. And with some mixes (beer and wine yeasts with baking soda and gelatine) I've had foaming problems so the air gap is important to keep.

As for less yeast, I don't think that will matter, the yeast ought to grow to fit their space. You might try a small insert on the end, maybe that will make a smaller bubble. A bottle with a smaller surface are at the neck could help, but I doubt it.

Meanwhile, I'm back to working on a substitute for the Hagen packets to use in their bottles -- such a nice design! If I can do that, and maybe even improve the rate a bit, that would be great, I'd keep that on the small tanks and do DIY in the tank with the mini vortex style reactor where multiple bubbles are not a problem.
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post #7 of 12 (permalink) Old 03-27-2003, 08:14 PM
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i'm going to try restricting the end of the tube.
good luck reverse enginearing th hagen packets
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post #8 of 12 (permalink) Old 04-20-2003, 09:22 PM Thread Starter
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Just an update on the effect of a HOB filter vs. a canister. I have removed the Penguin 330 (less biowheels) entirely and rely now on the Fluval 303. The pH had dropped from 7.6 to 7.1, even at a rather low bubble rate of 5 bpm on the DIY CO2.

When I had the HOB penguin, even with bubble rates in the 20 to 30 bpm range, I never saw a ph below 7.4.

So, it looks like the penguin was blowing off something like 14 ppm of CO2.
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post #9 of 12 (permalink) Old 04-21-2003, 03:39 AM
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my hagen ramps worked without losing co2 when the algae grew on the ramps, slowing down the bubles accent up the levles. but making a smaller hole dosn't = smaller bubble, not in my experiment. thats ok i dont need smaller bubble any more with two ramps and two 2L bottles I can get about 20ppm with a aqucaler mini costemized to reduce surface agitation; But i would still like to get a canister filter to help out /reduce the work of DIY
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post #10 of 12 (permalink) Old 08-08-2003, 01:47 AM
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Just an Idea, if you put a bell reactor over the Hagen ramps, so you dont lose any CO2.

I use a small glass Mayo Jar, it occasionally fills all the way up, but at least you have more CO2 disfusing into the water than just losing it completely.
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post #11 of 12 (permalink) Old 08-08-2003, 03:53 AM Thread Starter
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As long as the diameter of the remaining bubble is something like 1/4 the diameter of the original bubble, you have gotten 95% of the volume diffused. Pi x D squared where d = 1 or d = 4

Don't sweat the little stuff.

edit - too late at night! volume varies as radius cubed -- of course!

(Pi x R cubed)/4, if r goes from 4 to 1, r cubed goes from 64 to 1, the rest of the equation stays the same, so you have 1 64th left or 1.56%, with 98.4% dissolution. (I knew it was more like 98%!)
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post #12 of 12 (permalink) Old 08-08-2003, 10:36 AM
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The bubbles never completely disappear with my Hagen diffuser, but they get really tiny, and really slow going up the ladder. If you point the output from your filter or a powerhead in the general direction of the ladder, it will promote more dissolving. I noticed the bubbles were bigger at the top of the ladder when the diffuser was in a "quiet" spot in the tank. As anonapersona stated, it really makes no difference in the CO2 levels anyway. I had plenty in my 20g tank from one bottle of DIY no matter where I put the ladder.


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