# Drop Checker-A new way to use one



## Jim Miller (Dec 24, 2002)

Hoppy

That was a nice piece of work!

Congratulations!

Jim


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## plantbrain (Dec 15, 2003)

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.

Regards, 
Tom Barr


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## they call me bruce (Feb 13, 2011)

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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## Rockhoe14er (Jan 19, 2011)

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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## Hoppy (Dec 24, 2005)

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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## they call me bruce (Feb 13, 2011)

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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## Hoppy (Dec 24, 2005)

Rockhoe14er said:


> 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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## wet (Dec 21, 2008)

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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## Hoppy (Dec 24, 2005)

I got my color chart from: http://www.americanaquariumproducts.com/Downloads.html#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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## wet (Dec 21, 2008)

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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## Hoppy (Dec 24, 2005)

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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## Hoppy (Dec 24, 2005)

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.


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## sewingalot (Oct 12, 2008)

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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## Hoppy (Dec 24, 2005)

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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## wet (Dec 21, 2008)

Thanks sewingalot! It's a pleasure to give back to our hobby 

Hoppy -- re: copyright : I hear you. I think of such open and free licenses more as letting folks know this stuff is free to use, and you certainly belong on the copyright for this code!

In terms of yellow and color differences becoming agonizing, sometimes I think this is part of the pain of drop checkers. When I was testing my idea I found myself just having to walk away for a day or two at a time I got so aggravated...

Anyway, dynamic pH chart generation is now live at http://dropcheck.petalphile.com I'm using a resized version of the AP chart.

Here's an example of a 30ppm +/- 5ppm chart calibrated for "yellow." This screenshot omits the error message up top.









Here's an example for the same calibrated for "green."









No chart for you if there's only one drop checker being used.

I'll try to pretty-fy the forms next I find free time...


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## Hoppy (Dec 24, 2005)

I have been experimenting with drop checkers trying to get a short response time, and have it simple enough to DIY. After 7 different shapes, I finally figured out an elegant way to make one, relatively easily, that works good. It responds to very near the final colors in just an hour. The catch is that I bought a bunch of acrylic domes on Ebay to cut up to make it. Here it is: one hour after I stuck it in the tank.










Another couple of views:



















I can make these for about $2 in materials, and I have enough material now to make another 11 of them. Would anyone want to buy one, for perhaps $12 shipped Priority Mail? It would include a color card and instruction sheet. I'm not going to spend the time making them unless I know I can sell them or a reasonable number of them. Or, I can just do a DIY forum thread on how to make them.


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## macclellan (Dec 22, 2006)

wet - that co2 calculator is sweet. i think i found a bug though. when wanting to create a green solution, at say 30ppm, the text still reads "the perfect yellow" ... is 30ppm. If it is a formula for green, then a perfect yellow will be far more than 30ppm and would likely be very dangerous for fish.

hoppy - that's neat. do you think the quick reaction is due to the small volume of liquid or the shape (i.e. surface area) of the 1/2 dome.


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## Hoppy (Dec 24, 2005)

macclellan said:


> hoppy - that's neat. do you think the quick reaction is due to the small volume of liquid or the shape (i.e. surface area) of the 1/2 dome.


The time it takes for the color to stabilize is proportional to the volume of the fluid and the volume of the air in the air gap, and inversely proportional to the area of the air/tank water interface and the air/indicator fluid interface. So, the dome maximizes the air/water interface and minimizes the volume of air, and the "drawers" of fluids maximize their air/fluid interface and minimize the fluid volume. (Each fluid is only about 1 mL in volume). 

The typical blown glass drop checker has a large air/tank water interface compared to the volume of air, and, if you fill the ball half way with fluid, it has a maximum air/fluid interface with minimum volume. 

My dome design is faster reacting than the blown glass one because of the even larger surface area of the fluids and smaller fluid volumes.

I hope some of the Chinese glass blowers find a way to make this type out of glass, without charging too much for it.


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## wet (Dec 21, 2008)

Hey macclellan,

Indeed a bug incorrectly saying "yellow" when choosing one drop checker and the color "green": fixed and thanks!

Additions to the calc:
1) Added example of a two drop checker pic from patw.
2) Added credits for photos, etc.
3) Separate sections/accordion for Instructions, Calculator, and Credits.
4) "prettier" forms, if you want to call it that.

5) Centered the pH chart values.
6) Faster!

Hoppy,

Very cool design and kudos for tackling the slow response/speed issue.

Thanks!


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## sewingalot (Oct 12, 2008)

That is simply amazing. I for one would by three of them if I had the spare change today. Do you think it is possible to vary the dkh solutions to get a closer range?


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## Hoppy (Dec 24, 2005)

sewingalot said:


> That is simply amazing. I for one would by three of them if I had the spare change today. Do you think it is possible to vary the dkh solutions to get a closer range?


You can vary the KH solutions however you wish, but in the end, the accuracy is limited by the inherent inaccuracy in judging color differences. The ppm of CO2 is inversely proportional to ten raised to the power of the pH, so very small changes in pH make big changes in ppm of CO2, and the color chart is barely able to show differences of .1 in pH - and that varies with individuals color perception abilities. (10 to the 6.5 power is 79% of 10 to the 6.6 power, but that results in a color difference that isn't perceptible to most people.)

When I started this last effort I wanted something that would assure me that I had a significant amount of CO2 in the water with DIY CO2, but not enough to harm the fish. That's probably the best that can be hoped for, and I believe I achieved that goal.

Prior to the widespread use of drop checkers far too many people were too timid to raise their CO2 concentration high enough to be effective, stopping with less than 10 ppm in the water, while thinking they had over 60 ppm. Now we can use a DC to get the CO2 up into the 20-50 ppm range, then slowly edge it up higher while watching for fish distress. Even if we are too timid to do that edging up, at least we stop with significant amounts of CO2 and not insignificant amounts.

But, with DIY CO2 you can't easily edge the ppm up, so you really just need to know if you have a significant amount of CO2. With this design I think that is easy to determine. And, my first DIY CO2 bottle lasted 3 weeks, before the concentration dropped much, so I'm very happy with DIY CO2 for a 45 gallon tank. I'm glad I decided to try it and not just buy another pressurized system.


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## orchidman (Dec 15, 2010)

is there a way to calculate co2 just by checking the kH? or a i missing something?


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## Hoppy (Dec 24, 2005)

orchidman said:


> is there a way to calculate co2 just by checking the kH? or a i missing something?


There is no way to accurately calculate CO2 using KH, pH or any other water parameter. The only accurate way to determine the amount of CO2 in ordinary water, which has a variety of ions in it, is with a thousands of dollars price specialty sensing probe. Drop checkers get you in the right ballpark with CO2, but that's about the best you can hope for. (A drop checker uses the pH and KH of the fluid in the DC to measure the CO2 using pH reagent, but that fluid has only carbonate ions and CO2 in it that affect the pH.)


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## orchidman (Dec 15, 2010)

Ooh! 0.o i knew i was missing something!

thanks alot! ill be saving up for a drop checker. or saving up to do a diy


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## Zareth (Dec 13, 2010)

Very cool project, I might modify the concept a bit for my Mini M.

But you've got me wondering, what was the Drop Checker originally for if you, Hoppy, are the one who invented its current use?


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## Hoppy (Dec 24, 2005)

I didn't invent its current use. Dupla apparently originated that use. What I did was figure out how it worked, independently, how to optimize its use, and sell the concept to the planted aquarium community. That took a couple of years or so. The original "drop checker" was a pH monitor, using tank water so it indicated close to the pH of the tank water. ADA named their glass version of it a "drop checker". I adopted their name, figuring that was a universal name for it. But, ADA sold it as a pH monitor, not a real CO2 monitor. So, you could say I invented it the same way Bill Gates invented the PC. Me and Bill together own many millions of dollars due to our efforts:biggrin:


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## Zareth (Dec 13, 2010)

I see, very interesting.. And one more thing, is your profile picture darwin on a monkeys body?


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## Hoppy (Dec 24, 2005)

Zareth said:


> I see, very interesting.. And one more thing, is your profile picture darwin on a monkeys body?


Of course not! That's a self photo I took with a cell phone. :flick:


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## plantbrain (Dec 15, 2003)

Hoppy said:


> Of course not! That's a self photo I took with a cell phone. :flick:


Poor monkey

You can increase the transfer rate by placing the checker near some current, more current = reduced response times, no current= increased response time.


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