Here is a interesting fact or should i say partial question. I have run skimmers on ever single tank that I have run. I adjust the water extremely low so I barely get skimmate I mean change once a month or so. Now I never have phosphate or nitrate problems and everyone who knows me always wonders how my tank is so stable after what I put it through haha. so is the benefit from nutrient export or aeration?
Both.
Eric Borneman's article is a terrific resource.
Notwithstanding the value of bacteria as part of the food web (and as yet not noted their ability to bind up "bad stuff" like inorganic nitrogen , phosphate and organic carbon and some metals); skimmers are valuable in exporting them and other amphipathic organics.
Amphipathic organics are those chains with positive and a negative charged molecules which are attracted to water on one side and repelled by it on the other. These amphipathic organics are trapped in the air/water interface between the bubbles . This includes many bacteria which are exportable along with the "bad stuff" they have absorbed and consumed. Other organics binding nutreints and metals are also skimmable if they are part of an amphipathic chain. Thus, metals accumulations can be minimized as can nutrient levels via skimming bacteria and bacterial byproducts that hold them.
Even more of the hydrophobic (repelled by water)variety of organics are attracted to granulated activated carbon.
Other things like silicate and metals along with inorganic phosphate can be adsorbed by granulated ferric oxide.
OK,so skim away ;get those bacteria and their bad stuff out; sure but:
if too many bacteria or organics are stripped from the water via skimming or otherwise "bad stuff" can more readily accumulate in unskimmable forms like toxic free metals nitrate and phosphate with nothing to bind them and bacterial poulations may be stripped down to a point detrimental to the food chian. This also makes a good argument against UV sterlizers btw.
A balance is important,imo and experience. Tough one since you can't measure for it and it will vary form tank to tank given a variety of variables in different tanks including the types of animals kept there. Keeping lot's of available food for the corals etc. going in the water while exporting inorganic nutrients , keeping free metals very low and avoiding excess organics is the trick.imo.
FWIW, I use two relatively large skimmers an ASM4 x and a 4xx with a combined water pass thrugh of about 2400gph for the 600 gallon puddle I use to play with fish and corals.
I also dose organic carbon( vodka and vinegar ) in moderate amounts to enocurage bacterial growth andI feed teh 40 plus fish and hudreds of corals in the puddle system heavily. GAC and GFO are also used.
A broad variety of corals thrive even as massive amounts of bacteia and "bad stuff" in them are exported in lots of funky skimmate. Pods,larve bacteriaplankton and a host of microfuana are always present in the water column and polyp extension is good. Sponge growth is proliferous,even my encrusting goniopoa has grown along with the oregon tort. PO4 stays at or undr .05ppm with NO3 <.2ppm . I use no mechanical filtration, which I think would have more impact on cirulating food web items than a skimmer..
So for me it's about feeding the fish and corals ,calms and anemones and , feeding the bacteria to consume the "bad stuff" left over as the foods degrade . The bacteria also severe as a planktonic food source and support other microfuana . AT the same time enough export via skimming,gac, gfo without mechanical filtration is done to reduce inorganic phospahte , nitrogen and organic carbon to levels that don't support nuisance algae or harm invetebrates.
Aeration is important particulary at night when photsynthetic activity stops and and autotrphic organisms stop producing oxygen and start respiring CO2. Nightime hypoxia can harm corals and other oganisms.
Skimmers help here significantly and can help ,even more so when a CO2 scrubber is used with them,ime.
