I have a 14gal biocube with an ATS. I recently converted the 2nd chamber of the biocube into an ATS, but I have no idea if the ATS has been helping or not.
The biocube had been neglected and was completey infested with hair algae, similar to the photo in the other thread, but maybe even worse than that. There was literally a green field of hair algae on the back wall of the biocube as well as hair algae covering all of the rocks. The spaces between the rocks were even dark and full of hair algae.
I have had the ATS setup now for four weeks and the hair algae is almost completely gone, but unfortunately I don't know if the ATS helped much or if at all. The reason is, at the same time that I added the ATS, I also added 4 different types of macro algae into the tank. I probably went overboard on fixing my hair algae problem, but I didn't want to scrub or kill off the rocks.
After 4 weeks, the algae in the ATS finally starting to get some nice growth. I have been cleaning half of the screen once a week as recommended on the ATS forums. I was starting to think that the macro algae was starving out the ATS, but the hair algae that I used to seed my ATS screen is starting to grow back thicker each week.
I would guess that in a tank like my 14gal biocube, a big ball of chaeto would probably do better than an ATS in the 2nd chamber. I would like to go to just having an ATS, but I have grown fond of my macro algae test cube.
Skimmerless 14gal biocube: Previously a softie tank. Currently a macro algae/test tank. Inhabitants - 2 shrooms, 1 leather, about a dozen hermits, dozen snails, 3 pencil urchins, 3 brittle stars, 1 goby. Btw, the hair algae was so bad that all of these critters in the tank never dented it. The algae was getting worse even with all of the inhabitants until a week or so after I added the ATS and the macro algae.