All protein skimmers only remove 20% -35% of the measurable TOC regardless how much they cost from DIY to $$$$
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Copied from another thread:
FWIW, I contend that the data supporting that conclusion is weak. Not the data itself, which is fine for what it actually tests, but the interpretations that follow from it that many have expounded around the internet.
In the ocean, many organic molecules are added and reasonably quickly removed again from the water, by lots of different processes. Over time, what has largely resulted is a set of organic materials that are largely refractory to these removal processes, and they are only very slowly removed, some maybe only over centuries or longer.
So at any given instant, they may be the predominate organics present in seawater, but they are not necessarily those that are driving many biological processes, such as the carbon and nitrogen and phosphorus cycles that involve organic materials. The more easily metabolized organics are added and just as quickly removed. In this context, it might be a mistake to say that removing all of the total organics would be necessary to nearly completely shut down the biological processes involving organic materials. In fact, a reduction of only 10% in total organics might remove all of those rapidly turning over organic materials, and perhaps coincidently, those might be the ones that are most involved in at least some of the concerns of hobbyists with organics.
So in the context of these experiments, I wonder if the results would be substantially different if one started with tank water that was from an unskimmed system? Not just that the levels would be inherently higher and so might be more readily reduced, but that the actual types of organics may be quite different, and in some ways more reflective of the total organics dumped into the water column. In essence, skimming an aquarium may continuously remove those compounds that are more easily removed, and so leave behind those that are much harder to remove. Just as in the ocean then, we may have compounds building up that are resistant to skimming, and those may be a big portion of the TOC in a skimmed system. In that case then, it may not be surprising that when a study looks at how well a skimmer can remove them, you are looking at what is a refractory set of materials to start with.
I know the article made no such claims, but many folks may extrapolate the 10 or 20% removal fractions that were shown to say that only 10 or 20% of organics entering the water will be skimmed, and that might not be the case.
