OK, so I have my regulator and my reactor, now I just need the bottle to go full pressurized on my 55gal. I was going to go to a local shop and buy into a tank exchange but I noticed that they have multiple grades of CO2 available. They vary from "industrial" to "medical" to "research" with varying levels of purity. Does this matter much for a planted tank? Should I just get the inexpensive stuff (industrial) or should I be aiming for the purest CO2 possible?