when injecting Co2 you have to consider your Kh one of the most important factors. if your kH is 4-7*, then it will not flutuate enough to harm fish. if it is below that you should pay close attention to your pH and inject sparingly (less than 1 bubble per second)
Co2 is a great addition to any planted tank, your plants will grow better and greener than ever. i would start small, try using a DIY co2 generator with a soda bottle, and after a month you will really notice the difference maybe even less. if you like it, but dont like remixing every 2-3 weeks, then go ahead and get the one you are talking about, but i am very content with my DIY injector... find out for yourself