I've been running a skimmerless reef with a scrubber successfully for 10 months now. I have experimented as I went along, and would like to question some of the accepted methods used. I realise that often things that happen are specific to ones own system, and would therefore like to hear what others have to add to my observations.
The biggest discrepancy I have is that I feel that the screen only really kicks in after there is a weeks worth of growth on it. It seems that less water runs over the algae, but rather through it, once it is denser. This continues for up to 3 weeks of growth, when it really does become high time to scrape the screen as light penetration becomes an issue. I grow the screens between 2-3 weeks and have never had an issue of the lower levels of algae dieing and releasing posphates back into the system.
Pods eating algae? It has never once been an issue on my screens. If they do eat it, they have never left any holes in the screen. Which brings me to my last point. Why on earth would we want to clean our screens in fresh water? This sets the algae growth back by 24-48hrs in my estimation. I'm gaugeing this on the oxygen bubbles that form amongst the photosynthesising algae. It take 2 days before I see any bubbles after a fresh water cleaning. After rinsing in saltwater, there are bubbles present within hours again. Pods are present in the scrubber area all of the time, and move around very rapidly, so rinsing the screen in fresh water does not help, as new one will jump right back on as soon as the screen is replaced. Anyhow, the large ones that could possible eat enough algae to cause an issue(and I doubt this) have already been scraped away with the algae.
I'm currently experimenting with optimum lighting periods on the screens and will post on this once I have results. I want to see if 18hr on/ 6hr off is the ideal period, or if the algae continues useing nutrients in the dark phase as well, and where a 12 on/12/off cycle wouldn't be better.