Refugium -- Yay or Nay

[Reefin' Dude]

Let me put it this way. Only a percentage of what any given organism takes in will be utilized, a portion of it will always be waste.

Let us concoct a hypothetical example.
Animal 1 is able to utilize 80% of food item A, the remainder is excreted as waste.
Animal 2 is able to utilize 80% of animal 1's waste, the remainder is excreted.
Animal 3 is able to utilize 50% of animal 2's waste, the remainder is excreted.

let me put it another way. no organism is able to utilize 80% of what it takes in. lets take you as an example. i am going to assume you are an adult, done growing. lets say during the course of a day, you eat 3 big macs. are you saying that you utilize 80% of that Big Mac's mass? that means that 80% of the mass you take in, you maintain. that means that you would gain mass (weight) equal to all of that utilization. granted most of us Americans are overweight, but not to that extent. once an organism has reached its full size it no longer is increasing in mass (at least in an healthy way), the amount of utilized mass taken in as food is not longer increasing, it is replacement mass for dead and dying cells within the organism. the organisms is excreting as much mass as it is taking in. this is why i was saying that it takes an increase in population for an increase in the amount of nutrients to be taken in to work with what you are saying.

the total mass of the original food put into the system, has to be accounted for. whether it is in the form of detritus or the little utilized within an organism.

Assuming we only have 3 trophic levels in this example (there are usually far more), 100 units of nitrogen in food item A end up as 2 units of waste nitrogen that will likely dissolve. If we're talking about nitrogen, these figures are even rather conservative. Animal proteins usually have a PER over 90. Rather than ending up with 20 units of waste to be removed, we have instead allowed 18 units to transformed into potentially useful biomass.

we do not really care about N, we care about P. N can be off gassed, P can not. P has to be removed.

The same holds true for phosphate. The more life in the tank, the greater the potential for a given unit of P to be utilized. That P, then bound in that organism, has the potential to then end up as food for one of the organisms that we were originally feeding directly.

there is not a decrease in P through the organisms unless the organisms mass is increasing, either from the growth of that particular single organism, or from the growth of the population of that organism. unless the mass is changing, then there is not going to be a decrease in the amount of P through each of the steps. an increase in population is a sign that nutrients are increasing in the entire system. your example is proving that the amount of nutrients within the system is increasing. we need to be concerned with total P in the system, not just inorganic P. we need to understand the entire P cycle. just because we are able to test for inorganic P does not mean that this is the only P we have to worry about. we need to use the organisms in our systems to help us determine the actual trophic level of the system.

Given most corals have somewhat limited ability to utilize dissolved N, amino acids from food items are very important.

depends on the coral. SPS have developed the symbiotic relationship with the Zoax for these amino acids and dissolved N. we do not need to worry about it if the coral is in charge, and not the zoax.

The "oligotrophic environment" described (I assume you mean a coral reef) has FAR more food in the water than we could ever provide in our tanks. For corals in the wild, the vast majority of their macro and micronutrient needs, with the exception of carbohydrates, are acquired via heterotrophy rather than autotrophy. Though coral reefs are sometimes described as oligotrophic, they bare absolutely no resemblance to the freshwater bodies that term is most frequently applied to. They are sites of exceptionally high levels of primary production, have extreme density of life, and the water is filled with plankton.

do not confuse inorganic P with organic P. i think this is where you are getting confused. oligotrophic outer reefs are nutrient poor. meaning very little inorganic P or N. this is not saying that there is not plenty of organically bound P and N in plankton. the corals are eating this plankton. they are actively feeding. inorganic P and N are what is needed to start food chains. food for the algae and bacteria.

The point of a system designed for plankton production is to more accurately simulate the conditions found on a reef. More opportunities are there to convert dissolved nutrients into planktonic life and shed epiphytic material that is nutritionally useful to corals. Rather than being "nutrient export" as it is often described, it is a form of nutrient recycling. You can get more bang for your proverbial buck by turning waste into food, and encourage increased heterotrophy by corals to more accurately simulate the natural environment.

why create the planktonic life? just feed the planktonic life. if you feed the tank, then just supply the food you want and what the organisms you want to keep need. system grown plankton needs nutrients in order to be formed. if there is still food going into the system and this "plankton" is still being produced, then there is an increase in total P and N in the system. the system is again becoming more eutrophic.

why do we want to create heterotrophy? our tanks are smaller than what most of corals can grow to in the wild. how are we simulating nature, when the corals we keep are not found next to each other anyway? they are not found in the same proximity if we are trying to replicate nature within our exact dimensioned tanks. we say we are trying to replicate nature, but we are far from doing anything natural in our systems.

That is the point of inline refugia. It allows the creation of a separate biotope plumbed into the same system, allowing for a more accurate representation of both in the home.

these biotopes are not near each other in nature. we are creating an unnatural grouping of environments in close proximity. we are creating a compromise system for all of the inhabitants of the system. not well setup for a given biotope.

G~

 

[HillbillyYoda]

What was the question?