[kevmo911]

A 5lb cylinder contains as much CO2 as 25*88g cartridges (you linked the 20g system, which is less than 1/4th the size). How much do 25 of those cartridges cost? And, you either turn it on and off each day, or you leave it on 24/7. If you leave it on, you replace cartridges 3 times as fast, meaning it'll cost you 75 88g cartridges - or 340 20g cartridges - with that system to run as long as a 5lb clyinder (with regulator and solenoid).

On a nano tank, the cost over time is much slower to increase, and since nanos are often on a table or counter, there's no good place to hide the cylinder. And for a 5g tank, a 5lb cylinder could conceivably last 3 years, so a bit overkill.

Yes, that system will provide enough CO2 for any plants, carpet or otherwise, given sufficient light and nutrients. If (on a 5g tank) you turn it off and on every day, an 88g cartridge could last a month and a half. Full time, you'll replace every 2 weeks.

You can't use a solenoid for this thing because there's no regulator. The pressure in the line would build up to 800-ish psi against a blockage, and solenoids we use in this hobby are designed for (usually) a bit over 100 psi. And if you *do* turn it on and off every day, every day you'll have to tweak it to the right flow, and you risk killing off your betta, or shrimp, or microrasboras if you go too high.

An entry-level pressurized CO2 system with cylinder, regulator, solenoid, diffuser, and any extras will cost you in the $150-200 range. Unfortunately, CO2 ain't cheap to start. But the only cost over time is refills.

 

[kevmo911]

Okay, so you have pressurized CO2. At around 800 psi, give or take due to ambient temperature, CO2 turns to liquid, and liquid can't be pressurized. So 800 is as high as it goes. Normally, anyway.

A regulator takes that 800 psi and reduces it to something manageable, usually 10-50 psi, depending on how people want to use it. At this point you have a needle valve, which controls the flow of that 25 psi, giving you a specific volume of gas over a given time period. In between you can have a normally closed solenoid, which will open up the pathway for the gas when electricity is applied to it.

The kit you linked has a cartridge, which is a mini, disposable cylinder filled with CO2. I've always assumed it was pressurized (liquid) CO2, but heck, I've never actually tried to find out. Anway, there's no regulator. Only a valve that controls the flow of high-pressure CO2. It's like having a really stretched balloon and controlling the size of a pinhole in it. Because there's no regulator, and you're therefore working with maybe 20 to 40 times the pressure that we normally work with, the tiniest fluctuation of anything at all can affect flow. So it's cheap, and it's super-sensitive, and therefore pretty difficult to regulate.

And once you've digested that, here's a huge mass of information for you, starting with the basics:
http://www.plantedtank.net/forums/9...rums/9-equipment/946178-not-so-complete-compendium-pressurized-co2-threads.html

 

[kevmo911]

Correct me if I'm mistaken.. but I thought both the Fluval 20g and 88g utilized a needle valve to control working pressure? I realize the gauge on the 88g is for cylinder pressure. A solenoid would have to be placed after the needle valve on either unit unless you planned on doing some serious fabrication. Would that damage the needle valve or create build-up between it and the solenoid?

A regulator has a compartment (or two) between the inlet and the outlet ports wherein it lowers the pressure to a set amount. So, coming out of the outet you'll never have more than the set amount (say 20 psi in a standard case), regardless of whether there's a blockage. A valve controls flow, not pressure.

In the Fluval kits, there's no regulator, just a valve than opens and closes to limit flow. So there's still 800 psi coming out of the outlet, even through just a tiny pinhole. That means that in order to stop the flow, you'll need something that can handle 800 psi. We don't have any solenoids that can handle that much pressure while using a minimum wattage, at least certainly not in a reasonable price range. But that's okay, because the tubing would burst long before 800 psi.

You can have a solenoid before or after the needle valve; it really doesn't matter. We just usually run it before the valve because it's easier.