i wanted a small co2 reactor for my nano tank and i saw the mini vortex which looked pefect, but 50$ was a lot more than i wanted to spend. so i decided too make one. i bought a small powerhead for 8$, and used some extra filter sponge and a reallly tiny tupperware too build a reactor. i drilled a hole for the tubing with the co2 too come in. then i drilled a hole for the outlet of the powerhead. and i cut a hole on the bottom which i put the sponge over too let the already diffused co2 and water come out. here is a pic.