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Out of Column Drop Checker?

Discussion in 'General Plant Topics' started by Philosophos, Jun 11, 2009.

  1. Philosophos

    Philosophos Lifetime Charter Member
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    I've been thinking... why are all the drop checkers kept inside of the tank? They seem to do a wonderful job collecting algae, they're hard to read, and it seems smaller = better. Small size does not seem to make reading any easier, and small necks certainly don't encourage gas exchange.

    So why not have one that pipes outside of the tank, with a nice flat reservoir to maximize surface exchange, and a white background for easy reading?

    -Philosophos
     
  2. shoggoth43

    shoggoth43 Lifetime Charter Member
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    CO2 readings will vary wildly within the tank. That drop checker that reads as "enough" may show very little CO2 in the rest of the tank as you move it around to different locations. Perhaps Drop Checker should be changed to SPOT Checker?

    -
    S
     
  3. Tom Barr

    Tom Barr Founder
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    "Rough spot checker with a time delay" might be better.

    Like the pH/Kh chart, folks seem to rely too heavily on ppm's and test rather than plants.


    Regards,
    Tom Barr
     
  4. Philosophos

    Philosophos Lifetime Charter Member
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    Thanks for the support guys :rolleyes:

    I keep mine in one of the deadest parts of the tank, and try to push it as yellow as I can. If I see that it isn't yellow at the right times of day, I know by comparison my CO2 levels are dropping. From there it gives me the chance to do a check over the system before the plants even start complaining.

    The easier it is for me to read this, the better. Less equipment in the tank is always nice, too.

    -Philosophos
     
  5. VaughnH

    VaughnH Lifetime Charter Member
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    Once I find out about what bubble rate will give me too much and just enough CO2 in the water, judging by fish behavior and pearling, I don't use it anymore. It works best at encouraging you to raise the bubble rate up near the right level without worrying about the fish yet. After that you have to adjust the rate slowly until you find the right bubble rate.
     
  6. Philosophos

    Philosophos Lifetime Charter Member
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    Sure, I've moved mine around and kept it out too. I use it when I tinker mostly. All the same, it'd be easier/nicer looking to have the actual indicator fluid outside of the tank, with a nice white background and large surface area for quicker response times.

    -Philosophos
     
  7. VaughnH

    VaughnH Lifetime Charter Member
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    Yes, that is a good point, but I'm not at all sure the reading you would get would represent what was in the aquarium. It is hard enough to get anything close to an even distribution of CO2 in the tank, let alone in an interconnected container of water.
     
  8. Philosophos

    Philosophos Lifetime Charter Member
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    Ya, the longer tube would cause problems. That brings me to the other thought I had yesterday; In-line drop checkers.

    Hypothetically it would work by bypassing off the intake. One good curve to prevent splashing, and the air pressure would do the rest to keep the two separate. This would give an average of all water pumped through the intake, which is better than measuring a single point. It would also get the drop checker out of the tank.

    -Philosophos
     
  9. VaughnH

    VaughnH Lifetime Charter Member
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    If that inline drop checker was in the line coming from the external reactor, and if the water entering the tank was allowed to splash across the water surface (extreme conditions, of course), the drop checker could show 30+ ppm, while the tank water would have 5 ppm. Or, a much less extreme situation, but a very real one, the consumption of CO2 by the plants, and the loss of CO2 from the water surface, would mean the concentration in the tank is substantially less than in the return line. That could be handled by seeking the bubble rate that gives good pearling, but not fish gasping at the water surface, and using whatever the return line ppm was as the optimum reading. The mechanics of doing that could be tricky. I do kind of like that idea though.

    EDIT: Thinking a bit more about this:
    First, the water flow past the opening to the drop checker acts as a venturi to suck out the standard water/indicator solution, unless that flow is slowed way down first. Which leads to needing a flow straightening section, like a stack of small diameter pipes to force the flow to be near laminar flow. Then, the "drop checker" would need to be removable without opening up that return line, or the tank water would siphon out. Also, to get the right KH water so the color would be recognizable, would require numerous tries of different KH's (?). Then, many of us have our filter/reactor under the tank, so to read this would mean squatting down to see it. So, perhaps, a pH probe in the KH standard water? But, what about misting systems, where the ppm of dissolved CO2 is less than what the plants can access? Sorry for the string of consciousness muttering here.
     
  10. Philosophos

    Philosophos Lifetime Charter Member
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    I use drop checkers in the same way that I use lumens. One drop checker won't compare to another, just as one light won't compare to another. On the other hand, the same light or drop checker one day altering from the next will say something. I don't think calibration would take too much effort, assuming the difference is significant.

    I'm not sure the venturi effect would be something to worry about if it were on a bypass loop that changed diameter. With thin tubing, this could be done in such a way that would allow people to choose where they wanted to route the bypass for the sake of convenient viewing. Even if the narrow tube is 1/10th the diameter, at the rate many people filter, that's still an entire water column through every hour.

    Changing out the drop checker would be a matter of using a threaded collar after an on/off valve. You could even go with a modified quick release if you're feeling fancy.

    Misting would again be a matter of variables lost due to the limited observational ability of any drop checker. I don't think drop checkers are going to hit any sort of tautologies with empirical measurement here here, but that wouldn't be a first. PAR isn't PUR either.

    I do like the probe idea a whole lot though. It's an idea I remember you and Tom talking about, but part of the problem was getting it inside the drop checker. I believe you two were mentioning something like having an osmosis membrain going. I did a little reading on that wondering what happened to the idea, I'm guessing you had problems separating oxygen from CO2 because of relative atomic diameter?

    And please do mutter away, good critique is far more useful than mindless encouragement.

    -Philosophos
     
  11. VaughnH

    VaughnH Lifetime Charter Member
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    The problems I had with membranes were, first that it was very difficult to work with them. Then, I didn't get a fast response time unless I used a large diameter membrane with a minimum of fluid behind it, a thin layer. But, that isn't what would be needed to insert a pH probe - a definite water depth is needed for a probe. I dropped the effort when my frustration in handling the membranes and getting the fluid behind them got to be too much. I was never able to get a response time less than 15 minutes, as I recall, and that took more effort in assembly than I was willing to use for a response that was still not that good.

    Not long after that Tom discovered the CO2 meter he now has, which is 100X better than the drop checker idea can ever be.
     
  12. Philosophos

    Philosophos Lifetime Charter Member
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    100x better, but 10x the cost I'll bet. 15 minutes delay isn't exactly what I'd call horrific either. The fluids might be the sort of thing that could be done better by machine. Ever consider taking it to a larger company? Most hobbyists don't use the lab equipment available on the market, after all.

    -Philosophos
     
  13. VaughnH

    VaughnH Lifetime Charter Member
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    This would have to be a disposable drop checker, good for maybe a week or two before having to be replaced. I don't see a market for that. But, anyone who wants to take the idea and see what they can do with it should do so. I posted everything about my experiments as I went along, but I can't find it right now.

    The CO2 "Super meter" costs about 100 times what a drop checker costs.

    Unfortunately, this caused by brain to shift into gear when I least expected it! It is conceivable that micro-encapsulated 4 dKH water plus pH reagent, where the encapsulating film is gas permeable, could be made to work well. The "beads", being tiny spheres, would have the desired high surface area to internal volume ratio that is needed. That is way beyond my very limited capabilities. But, a simple holder for a batch of "beads" would be optically thick enough to see the color well, but would expose the "beads" to tank water. It would still have all of the basic weaknesses of the drop checker, except for having a much faster response time.
     
  14. Philosophos

    Philosophos Lifetime Charter Member
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    I was meaning comparing something like a hannah instruments pH meter along side your version of the membrane vs. the CO2 meter. I think every fish addict upgrades to a decent pH meter before anything else because of cost and application.

    So what you're thinking of is something like a strip test then? Impregnate a medium and let the colors change for instant readings, anywhere in the tank. Used properly through a growth/trim cycle with good, steady filtration, some one could get a working model of their CO2 flow between trim periods. Not a bad idea at all; I'd use it.

    Random thought... look at how the little storage caps fit on most pH meters. These get filled with storage solution. Why not create a tighter fitting one with 4dkh solution and membrane that attaches to the pH meter? It could be refilled for every reading. There may be delay, but having an accuracy of +/- .05 is a very large increase from a +/- .2 pH. This would allow for +/- 5ppm CO2 or better in the ranges we work with.

    -Philosophos
     
  15. VaughnH

    VaughnH Lifetime Charter Member
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    I looked at trying to make a "storage cap" device for my pH probe, but no good idea for how to make it showed up. And, the volume of fluid in the cap needed to cover the probe's active tip was too much to expect to get better than 2 hours response time, so I gave it up.

    One problem with gas permeable membranes is that water can pass through them as water vapor. In an aquarium this isn't a problem, but storing a probe with the KH fluid behind the membrane would require that it always be submerged in water to avoid losing water from the KH solution. That would be a major problem with a micro-encapsulated version too. If there was a big enough potential market I still think such a version could be made that would work well, but it wouldn't be a DIY project.
     
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