The AM CO2 1000. I ordered from BigAls for $62.99. I ordered a solenoid valve and a few other things at the same time.
I have been using a Duetto filter to act as a reactor, but it is very wastefull. I am having to use about 4 bubbles per second. Plus I leave tha CO2 running at night and just turn off the filter, so its more wastefull. (at the time I am getting CO2 for free, but I still hate to waste it!).
I am sure that when I get it (reactor) that I will probably need something else to go with it. That always happens, and my LFS stinks when it comes to anything "high tech". Hopefully it will work well with my Eheim 2026.