it would cost you about the same amount of money for a traditional regulator and co2 canister as the little paintball thing, but the traditional type will last you *much* longer and cost you less to refill. You have 75 gallons, that paintball thing is designed for desktop tanks. People really overestimate how much light they need to keep most plants happy, especially considering you need less the bigger the tank gets. Your tank is not going to do well unless you add some form of co2 to it and a traditional regulator/canister is going to be the most economical compared to the paintball thingie or Excel. You could also try DIY CO2, but you'll need several bottles of it going at once for such a big tank and you risk algae breakouts from the fluctuating co2 levels. Plus, it's a PITA at that point.