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Unread 11/11/2017, 06:47 PM   #17
Dan_P
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Join Date: Aug 2014
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Quote:
Originally Posted by tmz View Post
Very small particles like bacteria and phytoplankton are not pushed along but rather experience similar forces as molecules that adhere to the water air interface.


Why do you exclude upward flow as a force moving organics and small particulate matter upward. Upwelling is a part of how reefs work. Amphipathic and hydrophobic planktonic microrganisms and particulate matter are attracted to the air water interfaces but that does not exclude the effect of upward flow on them.
The upwelling of water in the ocean moves bulk water and it's contents to other regions. If the other region is lower in organic content, the concentration increases when the richer water is mixed in. It does not act at the molecular level to preferentially "move" molecules or at the micron level to move sub micron particles.

In the case of a skimmer, the upwelling is not water but air in the form of tiny bubbles. Aquarium water mixes with the bubbles and rises with the air into the skimmer throat. It is still just aquarium water mixed with air. Nothing additional has been swept along because there is nothing additional brought along but the material in the aquarium water. So very wet skimming is barely different from a water water change. The upward movement of water in the skimmer, the water entrained in the foam, is doing nothing to change the material concentration as it moves higher up in the skimmer column or skimmer thoat. The concentration of material we observe in skimmate is a result of the bubble breakage and the concentrated material reentering the water in the foam and re-attaching to bubbles, strengthening them which results in them lasting longer and eventually leaving the skimmer throat top. In addition, the water entrained in the foam drains away in the skimmer throat, also giving a dryer, more concentrated foam. Upward flow by itself is not part of the foam fractionation mechanism of concentration of molecules and particulates.


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