Hi all,
A lot has already been said in this thread, but SantaMonica asked me to comment and I do have a few things to add/clarify. BTW... while I personally don't mind, I can see where others may be irritated by a PM'ed request to comment on a thread.
My qualifications to comment: I have run turf scrubbers for quite a while. I have also used conventional refugia. While I haven't read the Addey book, I have observed dozens of turf scrubbers and discussed them ad nauseam with their owners. I have been giving a talk to local aquarium clubs about refugia and turf scrubbers. I will try to point out when my comments are based on my experience, are purely hunches or are what I consider to be fact.
First, to address the original point of this thread, which was the mechanical design of this particular scrubber... I like the idea of using both sides of the screen to get double the algae growth in the same or small footprint. however, lighting through the walls of the vessel will be a maintenance nightmare.
I would be concerned about the vertical arrangement of the screen. It has been well covered in this thread that the turf benefits from surge type water movement that allows the individual "fronds" to move to and fro, increasing light and water penetration. The vertical arrangement will inhibit this even with surge like water movement because gravity and the downward flow of water will mat the algae down. All that said, I did use a flat screen scrubber with trickle flow (no surge) that performed quite well.
IMO and IME, intermittent exposure to air is NOT necessary. The idea that air exposure delivers more CO2 to the turf doesn't Jive, especially if the scrubber is lit opposite of the lighting in the tank (a practice I strongly recommend). That way when the lights are off in the tank and the corals are respiring (producing CO2), the scrubber is scavenging it. The opposite is also true. IME, turfs grow slower with 24 hour illumination.
What I have found to be necessary is that the turf is always grown in a thin film of water and not submerged in more than a few millimeters. I have observed in my own DIY systems and in large commercial systems that when the screens are submerged, caulerpa, valonia, aiptaisia and other undesirable organisms quickly proliferate. I have also found that different systems favor different varieties of turfs. Morgan recommends seeding because he feels that his variety is more desirable, but I have found that even with seeding, a different variety may dominate. I don't think that's a bad thing, I just don't see a lot of benefit to seeding. My screens have always gone from sterile to their first harvest in about a month.
I have always run a skimmer with my turf scrubbers. It is a fact that turf remove few dissolved organics, and may in fact be contributing to the dissolved organics in a closed system (hence the often observed yellowing), so I still like to run a skimmer, even at the risk of skimming out some of the plankton from the scrubber. I also believe in regular partial water changes under all circumstances.
I have never had very good experiences with refugia and consider them to be maintenance headaches. I have always found turf scrubbers quite simple to maintain and quite bulletproof. That said, I know others who have had quite to opposite experience and hold the opposite opinion.
Last, but not least, I took exception to the same group of statements that others pointed out from the proposed beginner's post. In my refugium/scrubber talk, I point out that inflated expectations are one of the biggest problems with scrubbers and several of your statements were perfect set-ups for disappointment. Your pitch for scrubbers sounded more like Jim Jones passing out kool-aid than the nice lady at Costco offering someone a cheddar-wurst sample.
Hope this all helps.
Adam
