Substrates for pods
Hello - Just a few words about the pod piles, etc.
Copepods will seek out inner spaces for breeding and growth. Having a lot of surface area that can't be reached by fish will help them find this type of habitat.
Because the copepods are so small, they can utilize any small niche for this purpose. Knobby live rocks, spongy macroalgaes like chaetomorpha, or even sponges (see jeff keith's post on the amphipod bucket), all serve the same purpose - a place for the pods. The early life stages of the copepods, called nauplii (plural --- the singular is nauplius), like to graze on the bacteria on these surfaces. That is why new live rock may not have a lot of pods, they need to develop a biofilm to encourage the copepods to cling and graze.
Old live rock can be rejuvenated by placing it in old tank water, allowing the biofilm to grow, and adding pods. When you transfer the live rock to the tank, the pods will go with it, even though you may not see them all.
I hope this help clarifies the question of the purpose of pod piles.
About the nutritional content of the copepods - they are very healthy in lipids. After you drain the waterweight (which is about 80% of the animal), they are very nutritious for the fish. They contain about 30% lipids, and about 60% protein. A very small portion (5 to 10%) is inedible. Also, the water in the copepods body is actually packed full of Free Amino Acids (FAA),l the building blocks of the nutritious proteins. Free amino acids are easily digested by young and delicate fish, and are responsible for the development of healthy cells and membranes.
Adelaide