Combined chlorine is chlorine that is actively engaged in oxidizing goo from your water. The best remedy for it is ...more chlorine! It just means that the chlorine is doing its job. Usually if you have CC more than .5 ppm, we suggest shocking the pool until that CC level drops to zero. If it's less than .5, as in your case, just keep your chlorine levels where they need to be, keep the pool uncovered, and they'll take care of themselves. (By the way, there's no such thing as "chlorine lock", and the non-chlorine product they sold you was a really expensive way to do what you could have done with plain, generic bleach).

The FC and TC tests that we recommend are the DPD-FAS test kit (K-2006).(See the test kit link in my sig). It uses a scoop of powder to turn your sample pink, then you add drops of the reagent until it goes clear. No comparing yellows.... the complete kit is the K-2006, but if you have a drop-based kit already, the K-1515 is the standalone chlorine part of the kit. You can get them at a good price online using the Amazon link in my sig.

One of the main caues of slightly greenish but not cloudy water is the presence of metals. What is your source of fill water, and is there any known copper or iron in the water? Have you used anything containing copper (algaecides, trichlor tabs, any other type of "dual action" product) that contains copper?
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