You could acheive this without co2, but it will cost you more in the long run. You will have to buy 10 times the plants, and they will not grow as fast, nor as full without the co2. As to the CO2 nearly killing his discus, he probably had it set to put out too much co2. Also with plants you should turn off the co2 at night as the plants will respire (use O2, and put out co2), which will be very demanding, and if you don't have an air pump, or enough surface agitation it can kill very easily. If you get the semi-automatic co2, that is not nearly as expensive, and you can also get by without buying the reactor, and bubble counter. Check out Rex griggs site, he has some great DIY stuff, and I just built a CO2 reactor for my 135, which I will post up pics of later today. A pH controller is really helpful, but they are expensive, and if you can spend the extra time, you can hold off on them for a few months. The milwaukee 122 is a cheaper model that can be found for as little as 87.99.