Definately keeping the 23, according to Bob Fenner:
"If you're even vaguely considering an investment in any sort of meter, doser, denitrator, ultraviolet sterilizer... STOP, do not proceed to go; buy and use a small ozonizer in conjunction with your skimmer first. Almost all public aquaria utilize ozone with theirs; you should to. The chemical degradation of large organic molecules, responsible for off-color, turbidity, low oxygen and some toxicities by ozone make it's small start-up and operational costs pale."
He went on to add:
"Numerous authors cite the need for carbon filtration, venting to prevent ozone poisoning of livestock, and even hobbyists (!). These fears are largely unfounded. Though I would not directly introduce ozone into a system, the little that intended units produce is dissipated quickly when utilized in a skimmer. The worst that does occur with small ozone generators is increased corrosion of "rubber" materials in your system; well worth the many benefits. You, your fishes and house will not burn up or down, I promise."
I can get an ozonizer pretty cheap, but if it has a controller then the price goes way up... Think I really need one? I planned to use carbon anyway.