Automatic CO2 system with yeast

Experiment with DIY CO2 injection

I have a 20 gallon tank that I wanted to set up as a CO2 high light planted Tank
I started with a DIY CO2 using a 1 liter bottle. This worked well but I had to keep adjusting the Air line according to various factors. This makes it difficult to be away for any length of time.

I looked into preasurized systems but for a 20 gallon tank there where to many problems to overcome in making it reliable. First most regulators used for this are not really designed for aquariums, they are designed for horticulture. The problem with them is to get very low reliable flow rates. With the DIY system and a Hagen Ladder diffuser, About 9 bubbles per minute was good. With the top off and a cooling fan then about 15 bubbles per minute. Bubbles are not all the same. At 30 PSI a bubble contains much more CO2 then at the near 0 psi of my DYI system. Basically this means I would need about 2 or 3 bubbles a minute. Getting a regulator that could do this reliably looked to be out of my budget.
To solve this I deceided the best approach would be to use a PH controller.
When I looked at the cost of a CO2 bottle and regulator vs the DIY. The DIY cost me an average of 25 cents a week. As it would take many years to reach a break even point, I deceided stay with the Yeast bottle.

Here is my final setup, I haven’t tested the Relief valve yet as I have just ordered it.

I tried a cheap Chinese Normally Open solenoid but it got very hot and leaked making it useless. I could not find a decent Normally Open valve so I went with the Milwaukee MA955. This worked very well but with a major problem. Since it was Normally Closed I could not use it inline. I had to place it as a relief valve so that when it was activated it would bleed off the CO2 preventing it from dosing the tank. The problem is that in the case of a power outage, CO2 would not be regulated causing an overdose. To solve this I plan on adding a Relief valve set to around 2 psi so that I can hook the soleniod inline with the diffuser as shown above.
Now with the Silenoid hooked inline with the diffuser, with a power outage or stuck silenoio. it just cuts off the CO2.

Parts Cost (I paid)
Milwaukee MC 922 controller $85 (ebay)
Milwaukee MA 955 Solenoid $36.72 (rakuten)
Hagen Ladder Diffuser $10.90 (Amazon)
Control Devices Relief Valve VR25-100 $7.50 (Amazon) – adjustable from 0-20 psi
1/4 FNPT to 3/16 barbed $3.50 (Amazon)
Tom Air line Tubing Tee (4 pack) $2.99 (ebay)
Total cost is 146.61 for an automatic CO2 injection system that keeps ph within 0.2 and can be left unattended for 3 weeks at a time.

I just use regular air line hose, with the low preasure their is no need for special CO2 hose or special connectors
I used the CO2 indicator for convience but their is not really a need for one if you know the dkh.

The trick I use for inserting the tube into the bottle is to used barbed connectors such as the 1/4″ rainbird ones used to connect 1/4 inch tubing into 1/2 inch tubing. I just melt a hole into the cap with a Finishing nail, then use the drip hose punch to streach out the hole large enough that the barb can be pushed thru. This makes an air tight seal with out the need of Silicon or any other sealent.

With this system there is no need for an eloborate CO2 diffuser as conserving CO2 is not important, most of the CO2 is bleed off anyways. Their is no need to inject CO2 into your canister filter as this just adds extra wear to the impeller. The Hagan ladder works very well with the Yeast Bottle method.

This system should work well for up to 50 gallons or so.

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