Drop Checker-A new way to use one - The Planted Tank Forum
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post #1 of 30 (permalink) Old 02-25-2011, 08:34 PM Thread Starter
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Drop Checker-A new way to use one

Back about 4-5 years ago when I first began to work on how to use an ADA Drop Checker as a CO2 indicator I quickly decided that we should use a green color to mean "good", which meant a pH of the drop checker fluid of about 6.6. That was to let us see if we were too high or too low. Using 30 ppm of CO2 as "good" CO2, that meant the fluid had to have a KH of about 4 dKH. Then I never once reconsidered that aspect of using a drop checker.

A week or so ago I started using DIY CO2, and wanted a drop checker to verify that it was working well. For this I didn't need to see anything except that I exceeded some minimum amount of CO2 in the water, and it finally occurred to me that yellow is a much better color with that reagent. Yellow is easier to see, and the gap between yellow-green and yellow is smaller in pH. This thread shows what I did: https://www.plantedtank.net/forums/fe...r-diy-co2.html

To my surprise I have more than 20 ppm of CO2, but that also means I could have too much CO2, as unlikely as that seems. So, rethinking the problem, I decided that using two DC's or a two chamber DC would work best, with one becoming yellow when 20 ppm is reached, and the other when the maximum allowable CO2 was reached. Since we still don't have an absolute maximum allowable CO2 number to use, I decided to use 60 ppm as the absolute maximum - exceed that and dead fish would quickly follow. If yellow indicates 60 ppm, the fluid in the DC should be 2 dKH. With 2 dKH fluid 30 ppm would be just slightly green-yellow.

To test this I made a two chamber DC, using the design that pdavis41 showed in this thread: https://www.plantedtank.net/forums/di...p-checker.html which is a very flexible design allowing a very small DC to be made, which should also improve the reaction time. Here is what I made:


And, this is the chart for what the colors mean:


I loaded the two chambers with .75 dKH and 2 dKH fluid premixed with API pH reagent and installed in my tank. After only 30 minutes the two chambers clearly showed their final colors, and after an hour the colors stayed the same. Here is how it looks:


This tells me I have more than 20 ppm of CO2 and safely less than 60 ppm. I'm really pleased with this, and may save my pennies and buy a couple of the latest DCs from GLA to replace my crude little one. I'm convinced this offers enough advantages to justify using 2 DCs and making two standard KH fluids to use in them:
More accuracy,
Much easier to read,
Good for DIY as well as pressurized CO2

Hoppy
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post #2 of 30 (permalink) Old 02-25-2011, 10:01 PM
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Hoppy

That was a nice piece of work!

Congratulations!

Jim
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post #3 of 30 (permalink) Old 02-25-2011, 11:13 PM
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Good idea to target two KH ranges, but still a pretty large difference in the last reading, 23-60ppm.

I guess, I'll have to DIY the pH meter version for folks.

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Tom Barr




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post #4 of 30 (permalink) Old 02-25-2011, 11:16 PM
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hoppy , i'm wondering -do you sleep at night? thats great work--on one of your other posts you mentioned droping 1.0 of ph can increase your absortion of co2 by 10 my tap water is 8.0 ph and hard--dont have a reading I have my co2 cooking now maybe 3bps
and i barley moved my cheap red sea drop checker to kinda terquios in 10 hours--if i put peat in my fluval 305 will it drop the ph 1 point so i dont have to cook the co2 in my heavily plnted 45 gal tank?
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post #5 of 30 (permalink) Old 02-25-2011, 11:49 PM
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great idea. Why not use a dKH 1 and a dKH of 2 to narrow the range a bit? then you would have between 30 and 60 ppm
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post #6 of 30 (permalink) Old 02-25-2011, 11:51 PM Thread Starter
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Dropping the pH will have no effect on how much CO2 you have in the water. But, having CO2 in the water does drop the pH. If it drops the ph by 1.0, you increased the ppm of CO2 in the water by a factor of 10.

Using low light is the key thing. If you use low to low medium light, say 30-50 mms of PAR at the substrate the plants don't need a full 30-40 ppm of CO2 in the water. You can help the plants a lot with a lesser amount, say 10-20 ppm. Using drop checkers as I suggested lets you get into that range, with little worry about accidentally gassing the fish.

How are you diffusing the CO2 into the water? You should have an acceptable level of CO2 with that bubble rate.

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post #7 of 30 (permalink) Old 02-26-2011, 03:15 PM
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yes im difusing it with a red sea reactor 500 does that compared to one of those ceramic tube types ive been seeing around the web and 2 watts per gal 6500 k
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post #8 of 30 (permalink) Old 02-26-2011, 04:47 PM Thread Starter
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Quote:
Originally Posted by Rockhoe14er View Post
great idea. Why not use a dKH 1 and a dKH of 2 to narrow the range a bit? then you would have between 30 and 60 ppm
That would work better. I'm still playing around with this, to see how it actually does in the tank. Right now I seem to get yellow with both chambers of the DC after a few hours. And, I know I don't have 60+ ppm of CO2. I suspect the problem lies in the difficulty in loading the fluids in the two chambers. (It is very hard to do, largely because they are so small.)

Right now I'm leaning towards just using 1 dKH and one DC. That I can get to work ok. I much prefer the two chamber idea, but if I can't get it to work......

I think once you decide to go for yellow as the color you want, it opens up several different options. Now to find which option is best.

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post #9 of 30 (permalink) Old 03-01-2011, 02:20 AM
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Awesome.

What happens when pH drives below 6.0? Still yellow or does it change to new crazy colors?

This is similar -- and distinctly different -- to an idea I had a while ago about two drop checkers with different KH's, but I always stuck with assumptions about the color "green" instead of "yellow". The calculator for that is here for reference.

I like that you instead use much larger margins of error and have more faith in yellow than green, which makes sense to me. So, here is an updated (Beta) version of the above calculator that adds Hoppy-inspired options:

http://dropcheck.petalphile.com

It:

a) Lets you pick a margin from +/- 2.5, 5, 10, 20, 30, 40, or 50ppm

b) Doesn't make assumptions about the color yellow. Ie: if you're targeting "yellow" like your examples above, the calculator assumes the drop checker is at 6.0pH. (This is different from "green", which assumes 6.4 - 6.8pH looks "green".)

c) Has your image above.

If you like it, how about a bigger version of your color corrected pH chart? I can maybe make divs or a table around it to populate the CO2 numbers for ranges at that color.

Just ideas/tools to mess with to advance this idea. Those calculators can change and, as always, are driven by what users are looking for...
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post #10 of 30 (permalink) Old 03-01-2011, 04:01 AM Thread Starter
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I got my color chart from: http://www.americanaquariumproducts....tml#phlow_high There are undoubtably other websites with the chart, but that one came up first on google.

I like that calculator! I'm thinking about one possible problem: it appears that a KH below 1 dKH does not buffer against CO2 additions, which means the relationship between pH/KH/ppm of CO2 doesn't hold true, and the pH can have many values for a given amount of CO2 in the water. But, that 1 dKH is only a rough estimate given as such on the forum a few months ago. What if the real limit is 1.6 or 1.1 or .9 dKH? That prevents a drop checker from working with a KH below that limit, and makes it hard to use the yellow color as the indication color.

I now have a bigger 2 chamber DC in my tank, with 1 dKH and 1.5 dKH water in it, to see how well it works. It definitely does work to a greater degree than it did with .75 dKH and 1.0 dKH. I test it by first noting that the two chambers have different colors, from atmospheric CO2. Then it goes into my tank, where there is presumably about 20-30 ppm of CO2. It has to got to yellow for the low KH chamber and near yellow for the higher KH chamber. It did that ok. Next, I remove it from the tank and stick it to the outside of the aquarium. It has to return to atmospheric CO2 color levels. It comes close to doing that within a couple of hours. Now, back into the tank for a whole day or more. The colors should be different, one yellow and one not quite yellow. It seems to do that ok too. The problem is that the colors are very faint. With 2 drops of pH reagent the colors were barely readable. With 3 drops it becomes readable, but still faint. Tomorrow I plan to add another drop to each one, to try to intensify the colors some more.

The question about how low we can go with the KH should be easy to test, but I'm not quite sure how to do it yet. You can always blow through the water to add CO2, so that part is easy, but the rest of the procedure I'm still thinking about. It is a number we need anyway, so it is worth some effort.

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post #11 of 30 (permalink) Old 03-01-2011, 05:44 AM
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The calculator can look for and catch that threshold. Had some free time so, for now, moving forward with any calculation resulting in 1dKH suggesting the user adjust the target, range, or color. Still calculates, and we can move that number per your experiments.

Also alerts when the margin is higher than the target. (Negative CO2 bug-prevention.)

Lowered the margin to +/- 5 to 30ppm. Figured the person calculating for, say, 5 to 75ppm CO2 (+/- 35ppm) doesn't exist.

Do you mind updates/collaboration such as this? My thinking is the more people who try it, the better idea collected about good ranges, and calculators help with that. Elsewise I can move calculator stuff to a new thread. (Will get around to incorporating a dynamic color chart. That's really smart.)

Source and formulas, laxer than MIT license, avoided your email (crawlers) in the credit: http://dropcheck.petalphile.com/source All adjustable. Will add to github after making that less confusing. Maybe sooner
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post #12 of 30 (permalink) Old 03-01-2011, 03:44 PM Thread Starter
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I have no objections at all to any use or collaboration on anything that I post. All I want to do is put what I learn out in public so others can use it however they wish. And, that includes selling stuff. I'm too old to worry about things like patents, intellectual property, copyrights, etc.

I'm really confused now anyway. My two chamber DC, with 1 and 1.5 dKH water in it, has both chambers a bright yellow this morning. I can't believe that there is upwards of 45 ppm of CO2 in that tank. If there were, the loaches would show some signs of irritation, and they don't. What is nagging at my mind is the thought that it takes perhaps 2 dKH or more to buffer the water, so lower KH's won't work. I need to start experimenting to see if I can verify that. (Probably working downward from 3 dKH, which definitely does work.)

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post #13 of 30 (permalink) Old 03-01-2011, 11:14 PM Thread Starter
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I bought a new pH test kit, since my old one was a 2004 dated kit, and the drop checker now works like it should. I have 1.0 and 1.5 dKH waters in it. The difference in color of the two KH's is subtle, possibly too subtle. I'm thinking 1.0 and 2.0 would be better. Maybe I will try that tomorrow.

And, I'm still thinking about how best to test for the minimum KH that will buffer correctly - work according to the pH/KH/CO2 chart.

Hoppy
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post #14 of 30 (permalink) Old 03-02-2011, 12:54 AM
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Please keep this updated. I'm quite interested. Wet, that co2 calculator is fantastic! Thanks for taking the time to make it.

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post #15 of 30 (permalink) Old 03-02-2011, 07:10 PM Thread Starter
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I'm finding that it is agonizing trying to pick out the differences in color with my dual chamber DC at 1 and 1.5 dKH. I think I need to change it to increase the thickness of colored water that is visible, and definitely move away from 1 and 1.5 dKH. Today I may try to make a "thick water" version. I'm about to run out of acrylic though! And, I'm already short on cement - back to Tap Plastics I suppose.

The problem I didn't fully appreciate is that the colors with API pH test reagent become pretty faint near the yellow end. But, I keep remembering that Edison tested umteen thousand materials for light bulb filaments before finding tungsten.

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