Jerel and others,
Scrubbers and sumps full of Caulerpa seem to achieve the same thing, but a scrubber is different in many ways. When you're dealing with turf algae over Caulerpa, you are dealing with an entirely different beast. Turf alga are very very nutrient competitive alga. They'll go to town on your nutrient levels, believe me. The neat thing about them is, that they're growth rates can adapt to the change in feeding/stocking levels quickly. As for yellowing compounds being released into the water, that only becomes a problem when the reefkeeper gets lazy about scraping the screen. Growing turf algae is a bit more of a science than Caulerpa. They do best when exposed to both wet and dry environments repeatedly(think about the stuff growing on pier pilings). They also grow the fastest when kept short. Think about the tangs, snails, damsels constantly mowing algae turfs down on a reef. To co-evolve with this kind of grazing, turf algae have adapted to grow very quickly and uptake nutrients very quickly(otherwise they'd be toast). As the algae grows longer without grazing, the growth slows considerably. Thus nutrient uptake slows as well. Essentially, as long as you are diligent about scraping the screen(mimicking aggressive grazing), you'll have one heck of a nutrient uptake machine. But if you don't scrape diligently: an unmaintained ATS is about as effective as a skimmer that hasn't been cleaned. And yes, yellowing will occur if you don't scrape regularly(think Smithsonian, those ATS's would not get scraped for months at a time, hence why the reef went to hell). So the criticisms about ATS's only occur if the unit/algae is not maintained properly. And on that note, I'd wonder how well a skimmed tank would do if the skimmer wasn't cleaned for several months.
Caulerpa simply can't compete with turf algae. Furthermore, Caulerpa has other associated downsides. To get the same amount of nutrient uptake from Caulerpa against a given turf screen size, you'd have to have a lot more caulerpa and a bigger refugium/algae filter. Doug has already mentioned the risks about Caulerpa going sexual as well. Furthermore, as long as you maintain a turf screen, the turfs will not colonize your display tank. I can't say the same for Caulerpa, and have always needed a tang to keep the caulerpa in the display tank in check. But that's just my personal experience with Caulerpa.
Another fundamental difference between a refugium/Caulerpa filter and an ATS, is that critters like pods are not encouraged to grow in an ATS. In a fuge/caulerpa filter they are. By allowing pods to graze on the turfs, you are not exporting the nutrients. The grazing from pods simply reintroduces those nutrients to the reef tank. That is why a monthly freshwater dip is recommended for the turf screen. Again, they are both algae filters, but they are entirely different beasts. You have to approach them differently.
My point is this. Skimming is popular, and people often spend a good chunk of change for the super-skimmers(becketts) to get the best nutrient removal, right? The more you can export, the more you can feed and help your corals grow. Plus the more powerful the skimmer, the less chance of algae problems, etc.
Ok, so let's apply the same attitude towards algae filtration. Caulerpa works, but turfs are much much more efficient at nutrient uptake. Comparing Caulerpa to turfs is like comparing an airstone skimmer to a beckett skimmer. So, as more and more people accept the benefits of incorporating algae growth into their filtration methodologies(like caulerpa in the sump), and add to that the desire for bigger, better, more powerful... I simply hope the trend will got the same way. That eventually, people will want to incorporate something along the lines of an ATS into their system. Unfortunately, it's much easier to put a light over the sump and dump some caulerpa in, than it is to create an intertidal surge area for turfs to grow.
And 'that's the rub'. I hope to see Adey lighten up on the patents, or at least help encourage more people/companies to build ATS units. But I get the feeling that will not happen.
Fwiw, I love skimmers. And with my ATS systems, I always felt good about the fact that if one of my clams decided to spawn, I could hook up one of the skimmers in the closet to help remove the stuff if I had to. But I also enjoyed seeing the proliferation of life in the ATS tank without the skimmer. I had to see it with my own eyes, but yes indeed, the diversity in my ATS tank was much richer than it was in my reef that was skimmed alongside a refugium. Sponge growth alone was phenomenal. And I am not exaggerating when I say I usually had a few creepy crawlies on my arm when I was fiddling in the tank. And no matter how much food I dumped into it, I never saw any negative side effects. Like Eric B., I even began feeding insane quantities to the tank just to see what would happen. The only thing I noticed was that my fish were getting fatter!
I know Shimek believes that a skimmer will not remove pods and other active critters, but I was simply amazed at how much life developed in the ATS tank.
Shane,
I'll dig it up and scan it for you.
