If your interested in the subject I highly recommend the book Dynamic Aquaria: Building Living Ecosystems by Adey and Loveland.
I used algae turf scrubbing for about 8 years and I did find that it did do some nice things. These include great pod production, plankton production, rapid uptake of nitrates and phosphates, and easy maintenance.
I did find the following limitations, compared to the berlin system with a deep sand bed, which I use today.
Algae are generally "leaky filters". In other words, you get some slight discoloration of the water unless you run carbon.
I also found that the algae can become a big dirt trap. This can be counter productive, since all that trapped dirt has to be broken down by the algae. I would recommend some mechanical filtration before the water goes into the scrubber.
Originally I was not using skimming, and I found the overall water quality to be lower. This was because algae turf scrubbing had to deal with all waste products via biological filtration. Later I added a skimmer, and this did help the water quality quite a bit. When I'm talking about water quality here, I'm referring to coral growth and success with more difficult corals. If I was going to use algae turf scrubbing again, I would also use a skimmer, and skim the water before it got passed to the scrubber.
I also found that algae turf scrubbing does not mean that you will not have algae in the main tank. After all, the algae is releasing it's spores. It's growing in the scrubber, and it can grow very nicely in the tank.
I found I needed to harvest the algae from time to time. The algae grows in some massive mats, which is good and what you want, but large clumps of it can detach and possibly clog the output areas of the scrubber. Make sure the scrubber has a couple of different return paths at different levels, so you can tell if it's backing up.
Algae scrubbing works best when there is a back and forth flow of water in the scrubber. This is often done using dump buckets, or pumps using timers to alter direction. Think of this as sort of a wave action in a scrubber. It increases the contact time of the algae to the water, and keep the turf more open.
Over all, I have to say that I prefer my current system over algae turf scrubbing, mostly for the above reasons. However, I can see some cases where algae turf scrubbing would be the preferred method of filtration. For example, if you wanted to keep mandarins you'd have an ideal source of pods. Tangs usually do well in such systems, and you can use some of the algae turf to feed them, but don't over do it.
