Back...from a much needed vacation/holiday.
If your goal is water quality, then I suggest a deep sand bed, additional live rock, and chaetomorpha. I also use a couple caulerpas, but am probably going to stop using them. I suggest chaetomorpha because it is a fast grower and does not have the same issues regarding water staining and the chance of it going sexual and fouling your system.
I run a small bag of carbon in my sump to help, but I do notice that the caulerpas tend to taint my water a little.