I have to confess that I read your entire thread on the marinedepot forum since you said that was where all the pictures were. So I kind of cheated, all right, I really cheated. I'm assuming the the charles character over there is Delbeek. It's pretty cool that you are on that kind of basis with him. I thought that he had moved to the Georgia Aquarium when they were opening that. I'm either mistaken or he just went there to set it up.
Anyhow, great thread(s). I have one comment to make. I think that you are putting a lot of credence in your natural nutrient removal systems(DSB, turf scrubber, sponge filter, etc.). I just wanted to point out that you said that you were aiming for more of an SPS tank than your previous ones in your office. I saw the live rock in your tanks, it was pretty filled with filter feeders. The corals that I saw that were SPS, monti cap, somekind of staghorn, pocillopora, monti digis, and a few others, were fairly tolerant for being small polyped. My thought is that all of those filter feeders thrive in a tank with excessive nutrients. That is the cause for the cyano as well. Your water quality results account for this too. I think that you will find that without aggressive nutrient export, you are going to have trouble with some of the more delicate SPS and LPS corals that you are hoping to keep in this tank.
I think that the algae problems that you are having now are a direct result of not exporting enough nutrients. I know that you have had skimmer on the tank since before the sumps. I would tend to think that if it had been properly adjusted to skim well, was bigger, or was otherwise skimming very well, you would not have the algae problem anymore.
It is important to look at nutrient export as opposed to uptake. When you have organisms in the system that use the nutrients for growth, ie feed on the dissolved organic matter, they are not taking the excess nutrients out of the system. The nutrients are uptaken but not exported. They therefore, stay in the system and will later be excreted as waste, either when the organism that uptook them dies, or as a legitimate waste product. The beauty of a great protein skimmer is that it exports the waste. The excess nutrients are completely removed from the system when they are pushed into the collection cup.
The downside of the natural approach, the DSBs, turf scrubbers, aiptasia scrubbers, clam troughs, cryptic zones, refugiums, etc., is that they never remove any nutrients from the overall equation unless they also have a protein skimmer or frequently changed filter pads or socks. This eventually ends poorly, with the tank having so much extra organic matter that cyano is inevitable, as well as bad algae problems, high phosphate, and unsuppressable nitrates. The upside is the amount of diversity in simple invertebrates you end up with.
Plus, who wants to scrub that much algae on an acrylic tank with a snorkle on
I just thougt that I'd share some of my experiences and frustrations with them that I've had.