(By the way, I deleted a whole inbox full of pm's by accident about two weeks ago, so if you pm'd and did not get a reply, please retry.)
Wow it's great finding more old threads. Here's the most precise answer to the core question of how turf works, compared to skimmers; was from one of the original turf threads: "Algae can't use organic sources of nitrogen, and for the most part, can't use organic sources of phosphorus. They can only use inorganic nutrient sources." Taken from this long post from that long thread:
http://archive.reefcentral.com/forums/showthread.php?s=&postid=6006070#post6006070
This is why I wanted to get turf to work, because it only uses inorganics (NH4, NO3, NO2, PO4) which are the exact things we want out of our water. These inorganics are not "food" to anything else of interest (clams?). Also from that same post: "Algae can't use detritus as a nutrient source, at least not directly." Yes, another word for detritus is: FOOD. This point is exactly where I see the yes-skimmer crowd separate from the no-skimmer crowd. It's the thinking that detritus is BAD because is LOOKS bad, SMELLS bad, and much of it comes out of the rear of fishes. But look at manure for gardens: It LOOKS bad, SMELLS bad, and comes out of the rear of cows. But it's what makes gardens grow. Same could be said of compost, which is just rotting leftovers of dead things. If in a garden, you added manure or compost, and at the same time "skimmed" it out with some type of machine, it would seem counterproductive. That's what struck me as odd about skimming once I understood it. But at first, I too was telling onlookers "look out much crap my skimmer pulled out in one day!". This, at the same time that I could never grow any filter-feeders, and barely could grow non-filter-feeders. Grew lots of P and N however.
That post goes on to say: "Productivity is highest with turf algae, followed distantly (if I recall correctly) by seagrasses, followed very distantly by everything else (zooxanthellae, macroalgae, phytoplankton, etc.)" And he then shows this comparison from Perspectives On Coral Reefs (1983)...
Turf algae:
1.0 to 6.0 Productivity (g C/m2/day)
10.0 to 50.0 Area coverage (%)
Seagrasses:
1.0 to 7.0 Productivity
0.0 to 40.0 Area coverage
Zooxanthellae:
0.6 Productivity
10 to 50 Area coverage
Benthic algae:
0.1 to 4.0 Productivity
0.1 to 5.0 Area coverage
Sand algae:
0.1 to 0.5 Productivity
10 to 50 Area coverage
Phytoplankton:
0.1 to 0.5 Productivity
10 to 50 Area coverage
As for yellowing, someone in that thread said: "We added ETS skimmers to take care of some of the organics (generally added by the turf algae when the ATS pads were scrpaed of excessive algal growth)." So maybe yellowing is only during scraping, although as I said before I have not seen any yellowing yet.
Getting back to Morgan's input, I found this further down in another post: "Morgan was pretty adament that you need to use a specific type of turf algae for it to work." Well, I wonder if my new algae that is growing on my screen is going to be the right type, and how I might make sure to grow the right type. In another thread: "When scraping your screens, scrape off all other forms of algae growing on it but leave any turf algae until it out competes everything and is the dominant algae." Interesting. I did not do this my first scrape; I took off everything. I might try "selective scraping" when I do the other side, since it now has both turf and green slime. Another post/thread said: "It is very important that the screens are frequently exposed to air so that turf algaes are favored. There are poor examples of turf scrubbers at the Science Center. Their screens are constantly submerged under several inches of water, allowing valonia, aiptasia and macroalgae to grow and not effectively growing turf algae."
Well this got me concerned, so I took the screen out and "scrubbed" it in tapwater, using my fingernails, kinda like washing your hair. Tons of the green stuff came right off, and it seems to have left just the much-stiffer reddish brown turf:
Left side at 3 weeks, never scraped; first pic is before "scrubbing", second pic after:
Hi-Res:
www.radio-media.com/fish/ScreenLeft3weeks.jpg
Hi-Res:
www.radio-media.com/fish/ScreenLeftAfterScrub.jpg
Right side at 3 weeks, scraped 1 week ago; first pic is before "scrubbing", second pic after:
Hi-Res:
www.radio-media.com/fish/ScreenRight3weeks-1week.jpg
Hi-Res:
www.radio-media.com/fish/ScreenRightAfterScrub.jpg
Especially on the left (never scraped) side, you can see how the green slime was hiding the reddish-brown turf. So the question that remains is: Does non-turf algae help or hurt? As for "needing air", it makes sense for two reasons: (1) Real turf is found only where it is exposed to air; and (2) When you turn off your return pump and the water level in the display goes lower, the green algae that grows on the glass does not go past the water line, i.e., it is held back by the air. So I can see how more "air" over the turf can keep green slime out, and favor turf which is used to the air. Therefore I'm going to consider (as a future test) increasing the timer so the off-time is longer, allowing the turf to dry out more.
