A single Finnex Ray 2 will provide medium light at the substrate. Without CO2, you may be able to carpet using some of the easier, non CO2 heavy carpets. I am not experienced with the non CO2 carpets.
What you may be able to do is do a dry start with HC and get it very well established. You may be able to keep the carpet without CO2 afterwards. HC is difficult to get laying flat and spreading out without higher light and CO2 otherwise.