Many people report an increase in the population of Copepods and Mysids after installing an Algae Scrubber. This is because these lifeforms feed on and live in pockets of algae growth. They populate the screen so rapidly that they can consume the algae on the screen to the point of detachment. This is one of the reasons why the screen needs to be cleaned frequently, or at least rinsed in freshwater, which will kill off most of the baby copepods and thus lessen the chances of detachment. In the past, most of the time I would refer to compounds that are released from the algae into the water that might be beneficial to the coral, like sugars and/or amino acids. However I do not think there it enough information about what is good or bad about such compounds. However, the concept of an algal mat providing a breeding ground for life is not in question, and the benefit of this is not in question. A healthy pod population in your tank is a critical overall component of the system. Not only do copepods and mysid and the like consume like any other animal in the tank, they are also a constant source of food for other inhabitants of the tank. Many species of pods have a growth stage in which they are free-floating in the water, and during this stage they become food for all kinds of organisms in the tank. In particular of interest to reef keepers, among these organisms are coral polyps - more specifically, small polyps. Most also report a large increase in presence of filter feeders such as tube worms and sponges. These also feed on free-floating microorganisms. I think that too often the main focus of those in the Algae Scrubber "community" is that of nutrient control & reduction. Support and replenishment of the pod population as a result of running an Algae Scrubber is a benefit that could be held as completely separate from nutrient reduction, meaning that even if you don't have a nutrient 'problem', you may still have a nutrient cycle deficiency if your system is devoid of a healthy and diverse population of organisms. In order to encourage the growth of a pod population in your tank, it's a good idea to place some rubble rock near the outlet of the scrubber. It's a good idea, if you can, to gently swish the algae screen in the display tank before scraping to release pods (this would be additionally beneficial if you kept a mandarin). However, this is not always feasible depending on the type of growth you have. If you have a lot of slimy growth that tends to detach after you shut the flow off and then turn it back on or run water across it, then you might want to run your scraper gently across the top layer to remove this before swishing it. You may still get strands that detach, but you should not worry about this "seeding" your tank. The other option is to place the scrubber on top of the tank. For most, this is not feasible, and you are left with the only option being to place it in the sump and allow the effluent water to return via a pump. I've read various information regarding the survival rate of pods that travel through a high-pressure return pump, but I do not recall seeing anything conclusive. Some will survive, and some will not, but enough will survive to populate the display tank very well - otherwise, no one would be having explosive sponge and tube worm growth after installing a scrubber. And remember, no matter how your growth on your screen is doing, there are only a few basic questions that really needs to be addressed: Are your nutrients & parameters under control? Are your fish and corals healthy? Does your tank look good? If these are all "Yes"...then that's all that really matters!
