Randy Holmes-Farley
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My Tank Thread
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I wonder about the tiny bits of brine shrimp, mysis or whatever that get rinsed down the drain instead of entering the water column uneaten and then breakdown. If there’s phosphate locked up in the “bits” that is released when they breakdown as uneaten food, then rinsing is worth it for me. On a mature reef probably doesn’t make a difference as there’s plenty inhabitants to take up the “bits”
That thought may reflect a misunderstanding of what actually happens when something is "eaten".
If a fish eats a chunk of food, nearly all of the phosphate in it is released back to the water. It is not retained in the fish. For an adult fish that is not rapidly increasing in size, essentially 100% of the N and P eaten is released back to the water. The same happens in all organisms, including people. A juvenile fish that is growing will take up a fraction of the N and P it eats and make it parts of its own tissues, but much less than half is retained.
If organic compounds enter "the water column uneaten and then breakdown. ", the net process is not a whole lot different. Bacteria will retain a fraction of what they ate, and release the remainder.
In general, it makes little to no difference to the ultimate accumulation of nitrate and phosphate in the water whether a chunk of food is eaten by a fish, or it just "rots" on the bottom of the tank. nearly all of the N and P ends up in the water in either case.
This is a very important aspect of nutrient cycling that I tried to convey in the above-mentioned article that most people didn't not previously think through with comments such as the "benefit" of rinsing food, making sure it is all eaten, etc.
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