Organic acid.... I wanted to ask him what his take was on removing this in his "water-changeless" set-up. Not doubting it, but organic acid lowers the pH and discolors the water. A good skimmer would keep this under control but I don't have faith in a mud filter alone. It may be fine for super hardy soft corals, but I don't see too many of this hobbyists on this forum.
I think the reason the Sps in the original mud tank grew faster because of the excess nutrient, but lacked color due to the excess exposure to organic acid. Activated carbon will remove some, but not the amount a skimmer would remove. The mud would "feed" the corals with nutrients, but not provide the pristine environment that will allow sps to fully flourish.
The berlin set up would provide less nutrient to feed the coral and give it a good growth foundation, but would keep the acidification at bay and allow for more "pure" water.
Most sps care givers will find that if you let your tank get a little too dirty, corals loose color.
This is just a hypothesis.
