[Delphinus]

I think the connectors or fittings or whatever they're called are different for the paintball tanks than they are for the regulators that you'd use to control the CO2 bubble rate.

Having said that there is a kit (I forget who makes it, but you can get it at Elite) for FW planted setups that uses the paintball cylinders as the CO2 source for bubbling CO2 into a planted tank. I don't see why it couldn't be used for a reactor.

But then having said THAT, there are two downsides that I see: 1) the kit itself isn't cheap, it's like $200-300 if memory serves. I paid about $80 each for my two cylinders (one is a 5lb'er and one is a 20lb'er) so there's no costs savings in the end. And 2) Small cylinders kind of suck. They empty out pretty fast and while I don't know about the paintball cylinders, I found that it cost me the same to fill up a 2lb cylinder (I had a wee little 2lb cylinder for a while) as it did to fill up a 5lb or a 20lb. So there wasn't a whole lot of cost incentive to stick with a small cylinder.

If you're interested in looking at CO2 I think the thing to do is look around at the fire extinguisher places. My 5lb cylinder cost me $80 - it was a fire extinguisher in a previous life - they retrofitted the CO2 valve on it, hydrostat tested it and FILLED it for $80. Wow. My 20lb cylinder is a beverage machine thing. But I bought it off saltwaterconnection.com several years ago - I have no idea where you're normally supposed to buy beverage CO2 cylinders from. Oh crap, that was probably 5 years ago I bought that thing. I probably have to get it retested the next time I go to fill it.