CO2 schedule ?

[gardentank]

Oh yeah and avoid end of tank dumps at all costs! I'm looking for a 25 pound bottle to buy so I can swap my tank the second my main pressure begins to drop. I learned the hard way (killing the entire tank, including a group of 2 year old roseline sharks... Never again!!!) to refill the same or at least the next day as soon as I see a pressure drop. I look at the main pressure everyday and the second I see it move I shut it off. If you have a 55gallon or bigger or if you think you will want to run co2 to multiple tanks from one bottle in the future then get the biggest tank you can afford / find room for. Refilling a 5lb costs me 8 bucks and 25lb refill cost like 17 bucks. The price difference on the bottles themselves is like 80 or 100 bucks up front but worth it in the long run.

[Bedlamer]

I’m just starting to research CO2 systems for use with planted tanks. I’ve never used the yeast or bottled method before. I am familiar with gas systems used in SCUBA, paintball and medical O2. I’ve had a chance to briefly examine CO2 systems in some folks homes and in LFHs. Thank you to those who have contributed to this thread—it’s been a good starting point. I’m really not familiar with solenoids. I understand that SOVs are electro-mechanical valves that can be controlled by such things as pH controllers and timers. Does the signal from the timer or controller usually cause the valve to open or close—i.e. do they fail open or closed--or does it depend on the application?

If you were doing a money is no object bottled CO2 setup for multiple planted tanks—let’s say four of various sizes—do I have the following design correct—or is there something I’ve messed up?

Two bottles, one in use, one for a spare refill to have on hand. Master on/off valve as part of each bottle. Dual stage regulator i.e. one of these linked earlier http://greenleafaquariums.com/co2-re...regulator.html with quadruple needle valves and bubble counters option. Then four separate solenoids controlled by four separate pH controllers (one for each tank) to CO2 specific tubing to a one way check valve to more tubing then to either a diffuser or a reactor?

One thing I’m not clear on is the placement of the SOVs in the system—could they be as I described with the dual reg above or would it just be one SOV for the whole system and the quadruple outputs would just be for multiple diffusers on one huge tank if you wanted it run by a pH controller—and you would need four totally separate systems to run four tanks? Or the dual stage reg linked above would come with one SOV and you could easily add four more SOVs to provide for a four separate tank setup?

Thanks in advance for any input to help me get a handle on this.

[Complexity]

I've never tried to run more than one tank from a single CO2 system, but there are a couple of things I might can help with.

Each pH controller would need to have its own solenoid plugged into it so four pH controllers would require four solenoids. The pH controller is plugged into the electricity and the solenoid is plugged into the pH controller. When the pH controller measures the pH to be equal or lower than what you've set, it stops dosing the CO2 by shutting off the electricity to the solenoid. So in a way, the pH controller is basically an on/off switch for the solenoid based on the pH reading in the tank. Therefore, you cannot have four pH controllers, each reading the pH in four different tanks, without having four solenoids, as well.

How you can connect four solenoids to one regulator is something I don't know. Basically, the regulator controls the pressure that's coming from the cylinder so the CO2 doesn't come out all at once. Then the needle valve fine tune's the pressure from there. I don't know exactly how the solenoid works, but it's what connects the electricity to the regulator so it can do its job.

If you need four solenoids to run four pH controllers, and a solenoid connects the electricity to the regulator, it would seem you would need a separate regulator for each solenoid. The conclusion then is that you're not really saving much by running four regulators from one CO2 cylinder, so you might as well get four cylinders and run each system independently.

All that brings me to the conclusion that the there are only two reasonable ways to run four tanks with one CO2 cylinder. The first is to simply give up the idea of using a pH controller (and all that entails). The second would be to combine the water of the four tanks so that they're all running the same water supply. This could be done through combined filtration. Then the CO2 would be the same in all the tanks from the single CO2 system. The main concern there would be in ensuring that the CO2 embedded water (coming from the reactor) got distributed evenly in all four tanks. There are pros and cons to either method.

There may be other ways to do this that I'm not familiar with. It would be best if you could get in touch with people who have actually rigged up a system like you're wanting to give you some ideas of how they did it and what pros/cons they experienced with their setup. If you don't find anyone who can help, send me a PM, and I can point you to a couple of resources that might have more experience with this kind of thing.

[Totenkampf]

SOVs that are used in our systems need to be fail-closed. That way you can use them to kill CO2 on a timer at night, with a power outtage, or with a pH controller. The system you describe sounds nice for sure. You can even manifold the two cylinders together with two regulators, just set one 5 PSI higher than the other and one will be exhausted first (the other will only act to compensate for a pressure 'boost' when the primary starts to tail off.) this will allow you to have plenty of time to get a fill on one while no interruption of service. we use this trick on analytical equipment. Set it up as:

cylinder(s) -> DSPR(s) -> quad manifold -> SOV on each leg (if using four pH controllers) -> metering valve (better than needle valve)

note: pressure regulators control pressure, meedle valves control flow. set your PRs and THEN tune each NV for the BPS you want although this wont matter as much if you are using a pH controller. In this case the NV is a second line of defence from dumps (the dual stage regs and dual cylinder manifold will prevent this 99% of the time so a normal NV would be okay and half the cost of a metering valve) and will only control how quickly the pH will shift when the valve is opened. I still think slower is better and would set it up like you normally would without a pH controller. I have some high end DSPR made by the company GO and a couple ASCO continuous duty SOVs and 1/8" tube swagelok SS-SS2 metering valves that i was going to build up and sell. I may cut a deal for just the loose parts if you are interested.