Two updates:
1. The cyano stage: Some people, who start using a scrubber for the first time, get rid of their nuisance algae but then get some cyano that they never had before. The reason for this is that cyano is able to "fix" it's own nitrogen, which means it is good at getting the last nutrients that are available. However, once these last nutrients are removed, the cyano will go away too. And the more powerful the scrubber is, the quicker this happens.
2. High coral-growth theory: Some people are wanting faster growth with their
SPS corals. In a scrubber-only tank, when there are no other filters, you have higher amounts of dissolved and particulate food in the water than if you had other filters running. However, the lighting remains the same. In other words, growth requires light and food; a scrubber-only tank has more food, but the same light. My theory is that if you increased the light too, you would get much more growth; possibly more that natural levels.
This is based on watching "traditional" SPS tanks with lighting problems (low light/food ratio): The corals grow slow (if at all), and tend to stay brown. When the lights are fixed/replaced (high light/food ratio), the colors brighten up and the growth starts again. However a scrubber-only SPS tank has much more food in the water, yet still only has "traditional" amounts of lighting. So the light/food ratio is low again. So my theory is that if you increased the lighting to more than "traditional" levels, you would get "more than traditional" SPS growth. Bleaching is less of a concern in a scrubber-only tank, because of the larger quanitity of food that is available (studies have shown that more food reduces bleaching).
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