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Thread: Bactereial Counts: Skimmmers vs No Skimmers and GAC

  1. #31
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    Some nice detailed reviews by Randy and issue with the study

    An very interesting article and I’m very happy to see the data that does seem to answer some highly focused questions (such as what are the populations of bacteria in the water column of a reef tank). It is a very good starting point for trying to understand our systems, but IMO it is only a start. In many ways it seems to raise more questions than it answers.

    Please don’t take my criticism that follow the wrong way, but I am forced by my nature to point out some alternate hypotheses to explain certain observations. I also find some conclusions to be fairly weak, like the assertion of organic released from the Rubbermaid tub. It may be true, but is hardly proven and other possibilities exist.

    I’m a little concerned about how much it focused on water column bacteria, when there is little reason to believe that the primary processes being driven by carbon dosing involve such suspended bacteria. We at least need to acknowledge that the surface bound bacteria may not be behaving anything like the suspended bacteria in response to various manipulations (such as carbon dosing or skimming or GAC) and may be the drivers of nutrient reduction, oxygen depletion, pathogenic growth of bacteria and other microbes on or in organisms, and other processes that interest reefers.

    Most concerningly, the various hypotheses proposed to explain various effects ignored the surface bound bacteria entirely. Taking their unmeasured and potentially changing populations into account may have suggested very different hypotheses to explain observations. For example, the drop in suspended bacterial in Figure 10 after 3 days was attributed to depletion of other nutrients, when in reality it might equally be attributed to increases in surface bound bacteria expanding in population more slowly than the suspended bacteria, which after a few days begin to dominate the consumption of added ethanol (and expanded numbers).

    The article also ignored the uptake of dosed organic carbon on other organisms. Obviously the study was limited to bacteria, but it is well established that other organisms take up molecules like ethanol and acetic acid, and their increased growth may well be an important driver of certain effec5ts as well. For example, at very high doses of vinegar, I’ve food that zoox levels increased in various organisms (like an RBTA that became increasingly brownish), and their increased growth presumably contributed to some removal of nutrients from the water column.

    * In these experiments, the counted "bacteria" include any particle that meets the following criteria: (1) it is between ~0.5 and 6 um in diameter,*

    So any appreciably clumped bacteria are not counted. Clearly, this misses many bacteria, and in some cases, maybe critically so. When I dosed very high doses of vinegar to my system, the water became visibly cloudy, and more so as the dose was taken higher and higher. The whiteness was easy to see by eye, as were individual particles, in many cases, when looked at closely with the unaided eye. So that tells me that many of these clumps were well above the 6 micron threshold, and since each such large clump can contain large numbers of bacteria, the count may or may not be close to the total bacteria in such water. These large clumps may have formed in the water column, or may be shed from bacterial layers on surfaces (I can shake large clumps loose from my GAC when rinsing it), but they are certainly not being counted with a 6 micron cut off.

    Now I understand that the authors may not have had many such bacteria in their water, but one needs to understand that they can and do form under typical reef conditions. As a side note, skimmers may also be more effective at removing such large particulate bacteria clumps than suspended individual bacteria since they can easily remove particulates and such clumps may well have other hydrophobic detritus entwined with them to assist removal by skimming.

    * What is fueling this bacterial growth? Since we have already determined that the bacteria population in this aquarium water sample is carbon limited…

    Clearly, the tub itself (or organic material coating it) is providing a suitable carbon source for bacterial growth. *

    Uh, hold on. I have a substantial issue with this section discussing figure 11. It was determined that some were carbon limited. Some bacteria expanded by adding organic carbon. Why does that mean that the same or different bacteria cannot continue to feed on the organic molecules already present in the water? Especially in the absence of predation, the bacteria may simple consume the organics present and expand in numbers. I find the evidence for organics leached from the plastic to be speculative, and think the simple consumption of matter already in the water is equally plausible. Another possibility is simple release of surface bound bacteria tot eh water, not involving growth. The powerheads, skimmer (off) and container sides may harbor lots of bacteria that may simply be shed into the water, boosting the numbers, but not providing any source of readily metabolized organic carbon.

    The authors even noted this effect themselves later when they said

    “Over the first 10 minutes of skimmer operation, this value increased to about 100K/mL, presumably as a consequence of added bacteria from the tub/skimmer/powerhead setup. Despite this initial surprising data point’

    Although they did not apparently go back and apply that knowledge to other experiments where such equipment could have been a bacterial source.

    The logical experiment is to add tank water to a totally clean glass vessel and monitor bacterial counts. Measuring the TOC in the no ethanol dosed “control” may also have helped answer this question. Going up means a source of either organic carbon or whole bacteria. Stable or going down suggests no source such as the plastic.


    * Thus, GAC does not seem to be an effect method for removing bacteria from the water column of reef tanks.*



    So what? They are clearly an excellent way to removing benthic bacteria growing on the GAC. Rinsing my GAC results in clouds of white bacteria released down my sink drain. Why do we need to reduce those in the water column to make GAC a useful way to export bacteria? We need to keep a vision of the whole reef system, not just focus on the experiments that were run.


    * It is likely a significant observation that there is a floor in aquarium water bacteria populations that skimming will not breach. Perhaps in both water sources, the SJ 55 na´ve tank water and the KSF modified (or not) tank water, there appears to be two functionally distinct populations of bacteria; one that is susceptible to bubble-based removal, and one that is not. *

    Maybe. Probably every species is a little different, and maybe even many phenotypes of a single species are different in skimmability depending on glycosylation of their surfaces. But alternatively there is a source of ongoing release of bacteria from surfaces that maintains some in solution regardless of the ongoing removal. This is an example of where I think ignoring the benthic bacteria focuses the interpretations into a single answer when there may be others.
    [


    There is allot of meat here for us to chew on
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  2. #32
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    Quote Originally Posted by Boomer View Post
    Skinny you did not add ANY healthy criticism like the last posters have.

    Ironically enough, Feldman himself even admits it's incomplete, that more research needs to be done, so hats off to him for that.

    And he has said so in all his articles. It is called getting things started as did I. Where did you get the notion it was complete ? Neither I nor Ken ever claimed that. Now you are praising Ken.
    the anti-skimmer sentiments and notion of the completion of the study came from you! in your first post: "I just love it when all he lines connect to the dots. Skimmers get beat up more by Ken." so blame yourself for that whole line of discussion. I dont actually think the study says/proves anywhere you should turn off your skimmer... hardly a "beating".
    My addition of skimmer opinion was just to answer your initial jab at skimming with that comment, not because i thought the study said not to skim.
    Then you basically inferred that I only have criticism because I sell skimmers, so hence my bringing them up again..
    As I said, a couple times now, my issue is with comparing the ocean to closed systems (in this case) in an attemt to judge proper bacterial amounts in a reef tank. Synthetic sea salt in a box isnt the ocean, you can just interchange results from both as a means to prove theories or anecdotal observations...
    and yeah, I praised feldman because he was at least being humble... and I will also praise randy holmes farley for lucid comments/questions about the study. ...perplexed??
    Last edited by Skimmy; 03-07-2011 at 04:21 PM.
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  3. #33
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    Yah that is what I thoguh a skimmer salesman, where you just can not handle some truth can you as it HURTS your sales. That is ONLY why you are on this thread. You must think we are all stupid.

    the anti-skimmer sentiments and notion of the completion of the study came from you! in your first post: "I just love it when all he lines connect to the dots.

    Odd how you make things up as you go along. I never said or implied I'm anti-skimmer so get that out of your head. The issue is skimmers DO NOT perform as often claimed, IS THE POINT. Many have shown this and YOU just dont' like it. Nowhere, did I Ken or ANYBODY say remove your skimmer. It is all about skimmer hype for sales which is misleading to hobbyists for the purpose of sales. And nobody is comparing a reef tank to the ocean where did you dream that up ? Ocean data is just a ruff guide when it comes to reef tanks. You are only praising them now as you look bad from your last posts about them, so oop's I Skimmy dug himself some post holes. Before they were a bunch of of meaningless useless scientists. Get you ducks in a row. I will say it for the last time you have added nothing to this thread like the rest.
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