Yes you can use CO2 and fertilizers together. Many many folks here inject CO2 one way or another. It is the only way that some species of plant will thrive. Even if you have undemanding plants, CO2 still does not hurt anything.
There is also Flourish Excel which is an alternative to injected CO2, it's liquid form that you dose every few days. If you go this route, be sure none of the plants you have are sensitive to it, and be sure to follow the directions as overdosing can be detrimental.