In news empowered us with this mighty blow against the
Patriarchy:

I found its instructions in PDF format on the web.

(1) It's only rated for 20 gallons. Does it seem like it would be
enough for 30?

The reaction chamber didn't produce enough CO2 for my heavily-planted 29
gallon tank. I kept the diffuser (good product) but replaced the reactor
with my usual 2 quart juice bottle. YMMV.

(2) It has two separate packets of stuff that have to be replaced
monthly

Yeast and a "stabilizer" which is probably baking soda meant to keep the pH
of the mixture up. Both can be bought much more cheaply at your local
grocery store.