I have just been reading about a reef keeper who has run an algae scrubber for 10 years. He said it has worked well, and the only long term problem was a build-up of phosphate. I suppose this would make sense if you follow the nutrient uptake ratio of 16 parts nitrate to 1 part phosphate used by algae. Is it reasonable to assume then if we dose nitrate to our tanks we can overcome this nitrate limitation and consume much more phosphate.