Refugium thoughts

I have been thinking recently, as I have from time to time over the years, about how to maintain significant planktonic life (both phyto- and zoo-) in my tanks. What I repeatedly come down to is that the conditions that we maintain in our tanks to keep various livestock does not match the conditions needed to maintain planktonic life. It seems that the natural tendency of our systems is to consume available nutrients, including plankton over time which results in low nutrients and bio-diversity. In addition, several pieces of equipment that we use tend to remove or destroy some of the life (protein skimmers, UV, ozone, pumps, etc.). Yes, I think most life will make it through an impellor, I have seen small fish make it though, but it certainly does not help. Several pieces of equipment and thoughts have been put together to improve this, such as refugiums. However, it seems that a refugium suffers the same loss of bio-diversity and, over time, does not provide many of the benefits that we add them for.

Usually when I have a question if something will work in my tank, I think to the ocean and what is occurring there, and then translate that to the best of my ability to my micro-system. This helped me in my early days of reefing (the 80's) when the lfs gave advice that did not make any sense to me (it has a large mouth feed it goldfish, or it has a small mouth feed it brine shrimp), but that's quite enough of those chilling thoughts... My goal with my tanks is to mimic the natural environment as much as possible, and I think that providing a constant natural food source is one is the largest things that I can do to accomplish this. Eventually I adopted refugiums to increase biodiversity and add to my plankton levels. But, I feel that they have one major flaw in our closed systems: nutrient levels will be the same between the main system and the refugium which limits production. I have noticed over the years that various 'pods and other plankonic like needs to be added to the tank on a fairly regular basis in order to maintain populations to feed the tank. It also seems to me that a refugium, as they are usually implemented into our systems, are not very useful beyond adding volume and the ability to house incompatible species in the same system.

Thinking back to my original mantra 'what would I find in the ocean' it seems that the area we call a refugium (tide pools, mangrove patches, etc.) is much much larger than what we would call our display (portions of the reef proper). And even if I had the space, I would probably not install a massive 'refugium' (let’s say 1000g) for a small display (let’s say 100g), although I think that a refugium that is 10x larger would probably provide a reasonable food source for a display that size.

From time to time I go through this thought process and I have always come down to the same theory: The only way I can provide and maintain as much planktonic life to my tank as I can is to culture it outside the main system. As a result, I have cultured various species of copepods, mysis, rotifers and phytoplankton to add to my tanks. It seems to me that this is the only viable way to keep and maintain planktonic life in my tanks, although it is limited to the species that I choose to culture.

While I think refugiums are beneficial, it is limited to being able to maintain non-compatible species together in the same system (macro algae and tangs, or feather dusters and butterfly fish). The refugium will be as nutrient poor as our display system.