Most popeye will clear up on its own with not apparent long-term damage. It is commonly caused by a trauma to the eye. ie, netting, running into rocks, fighting. Go to some more established forums and look up carbon and/or clownfish. I personally added carbon after reading some of the article. It was the first time I actually used carbon in years, 4, maybe 5. within 2 weeks, my female clown had popeye. Does the carbon cause it, do the clowns get restless and clumsy, bump into rocks, etc, i do not know. There is a mystery here that one day i would like to better understand, but my clowns are mating regularly. I'm not about to test it now. Hopefully we get somemore feedback to your original question, what is the best carbon to run.
by-the-way, after running the carbon, "marineland Black diamond" for a couple of weeks, when i performed a water change and looked at the water in the waste bucket, it was clearer than i have ever seen it.
uwscotch