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Discussion Starter · #1 ·
It is quite easy to make your own "Drop Checker" or CO2 Indicator from acrylic sheet. The object is to have a small device that holds a few ml of water/indicator solution under the water line of the tank, so there is an air gap between the tank water and the indicator solution water. The commercial versions of this range from the elegant ADA glass unit, which is currently out of stock, to a much cheaper imitation ADA glass unit from Hong Kong, to a Red Sea plastic unit which is still cheaper. All do the same job. Two of the commercial versions are the imiitation ADA unit:


and the Red Sea unit:


Both are available on ebay at: eBay: Type2 Co2 Drop Checker-monitoring proper dosage of CO2 (item 250038130859 end time Oct-18-06 09:05:18 PDT)
and eBay: CO2 Indicator Red Sea Real Time CO2 Monitor (item 300036151186 end time Oct-14-06 09:48:10 PDT)

The easiest way to DIY this is to use all straight lines and rectangles, and make it from acrylic plastic. I made one a couple of years ago, but hadn't figured out how to effectively use it so I tossed it. Here is what it looks like:


All of the pieces of acrylic have to have squared edges, and the pieces that establish the thickness of the device should be cut from a constant width strip. When glueing these together, remember, the assembly has to be air and water tight, and any smearing of the cement makes it hard to see the color of the indicator solution. For an indicator solution you can use the solution from an Aquarium Pharmaceuticals pH test kit, or any other test kit that gives yellow at pH=6 and blue at pH=7.2 - use at least double the number of drops of indicator solution as the kit says to use, to get a more intense color. (Using even 4X the recommended number of drops doesn't change the test reading, only the intensity of the color.) To use this see:
http://www.aquaticplantcentral.com/...it-work-ada-glass-dropcheck-3.html#post236934
 

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Discussion Starter · #3 ·
The reason for setting the KH of the indicator solution to 4 is so that with 30 ppm of CO2 the indicator color will be green, and an unequivocal green. That gives the maximum accuracy. If you had a lower KH, the 30ppm color would be near yellow, almost impossible to judge, and if you had a higher KH, the color would be blue green, again very hard to judge. Actually, any KH that is within .5 of 4.0 will work, but 4 seems to be just about the perfect KH. Since it is easy to get the KH to whatever you want it to be, as accurate as you want it to be, why not shoot for 4.00 KH? (You can even use 10X the usual water sample size, so that each drop of KH solution will equal .1 degrees of KH. I used 4X and could judge it even closer by noting how nearly each drop came to tipping the color over to yellow. (I use AP test kits)
 

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Discussion Starter · #5 ·
Yesterday I cleaned up the GDA, changed about 90% of the water, tossed most of the BBA infested plants, bleach dipped the anubias and java ferns, etc. and I took another photo of my "drop checker" in action:



Notice that it is running a good green color, meaning I have 30 ppm of CO2 in the water, early in the morning. I love that little bit of glass!!
 

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Discussion Starter · #8 ·
It is hard to know what the best ppm of CO2 is, since the numbers people use are all based on measuring pH and KH of the tank water, which is not an accurate method, due to the other things besides CO2 that affect acidity and alkalinity in our tank water. You can choose the ppm of CO2 you want the indicator to be green at, by adjusting the KH of the distilled water in the bulb. I picked 30 ppm believing that to be at least not too much. For that I used KH=4.0 in the bulb. I am thinking about raising the KH to maybe 5 later, to get green at 40 ppm, and if that is still ok, going to KH of 6 to get green at 45 ppm. This would be a way to finally determine what the "best" ppm of CO2 really is.
 

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Discussion Starter · #10 ·
Here are the color charts for the three commonly used pH test kit reagents. For the top one, it is yellow at pH of 6.0, blue at 7.2, and green (the middle) at 6.6.

 

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Discussion Starter · #12 ·
This works because a sealed container of air in contact with water will reach an equillibrium amount of CO2 that is at least proportional to the ppm of CO2 in the water. So, two containers with their water in contact with the same sealed container of air will reach the same ppm of CO2. The "drop checker" has distilled or DI water in it, with a known KH obtained with bicarbonate only - no other source of alkalinity, and no source of acidity. That makes the equation that is behind the pH/KH/CO2 table work correctly (see Chuck Gadd's website). So, if we can measure the pH of that little bit of water in the "drop checker", and we can, by using a pH indicator solution, we can accurately calculate how much CO2 is in that container of water, which will be the same as is in the tank water, since they are connected with a sealed air column. At KH=4, and 30 ppm of CO2, the pH will be 6.6 which turns the bromothymol blue indicator, used in almost all pH kits, green. So, green means you have the right amount of CO2 in the water, and yellow green means you have too much, while blue green means you have too little.

There is no way for the indicator solution to migrate to the tank water, since there is an air gap separating it from the tank water. If it did get into the tank water, it would be about 4-8 drops of a 4% sodium hydroxide in water solution with a little bit of bromothymol blue dye in it. It wouldn't be desirable to have it mixed into the tank, but I doubt it harming anything if it were mixed in.

So, to use this:
First, get some distilled water from the grocery store.
Using clean glass container, pour about a cup of that water into the container.
Next, add a very small amount of bicarbonate of soda - baking soda - Arm and Hammer soda, etc. to the water and stir it up with a very clean stirrer.
Test the KH of that water with your test kit.
Most likely it will be a higher than 4 KH. So, add some more distilled water and repeat the test. (If the first KH comes out to 8 degrees KH, double the amount of water. If it is 6 degrees of KH, add 50% more water, etc.)
When you get close to 4 degrees KH, repeat the test using twice as big a water sample in the vial as the kit calls for, then count each drop of KH reagent as being half the degrees of KH that the kit normally says - for AP test kit, that makes each drop equal to .5 degrees KH. I found I can get very near "exactly" 4 degrees KH by doing this carefully.
Use a syringe to squirt some of this 4 degrees KH water into the bulb of the "drop checker". Fill the bulb about 2/3 full of the water.
Add a few drops of your pH test reagent - use enough to get a strong blue color, but not so much that the water becomes opaque with the blue dye.
Use the suction cup on the "drop checker" to suspend the device two or three inches below the tank water surface, with the "horn" of the "drop checker" pointing down so it traps air in the horn.

After a couple of hours or so the color of the "drop checker" fluid will be at about the equillibrium color, and that should be green if you have 30 ppm of CO2 in the water. If the color is yellow, you have at least 70 ppm of CO2 (and your fish are in serious trouble!). If it is blue, you have about 10 ppm of CO2, which is not nearly enough.
 

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Discussion Starter · #16 ·
Functionally, they have to all be the same. But, esthetically there is a difference. I think, from looking at the photos, the "type 1" is a more direct copy of the ADA unit, while the "type 2" is produced by a different glass blower, and less effort was put into matching the appearance of the ADA unit. The teardrop shaped one is still another glass blower's interpretation of the idea. It looks very good, but I doubt it having as fast a response to changes in tank water CO2, since it seems to have a much smaller tank water interface (no "horn" to increase the surface area of the tank water being interfaced.) That last one would be much easier to load with water and indicator solution, and might satisfy some people much more for that reason. It is pretty hard to get the water and indicator into the "type 1" verson, and nearly impossible without a syringe with a bent "needle".

What is encouraging about this is that apparently this fellow in Hong Kong is selling these well enough to branch out into other versions. Maybe our discussions involving ppm of CO2 in the water will become more meaningful as more people use these.
 

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Discussion Starter · #19 ·
I got mine installed and working. The hardest part was getting the RO/DI water to 4 dKH. I think I spent about 1 hour doing this (add baking soda, more baking soda, more water, etc...). It was a little difficult getting the water/indicator in until I realized that the old pipettes from Seachem Flourish bend right around that tight curve and squirt it right in the bulb.

It is a very cool device that gives you a good indication of the CO2 levels at a glance.

Thanks for being the guinea pig and trying this out for us \\:D/ .

Brian
Thank you for biting the bullet and trying it too. I am now running mine with 5dKH water in it, so green means about 40 ppm of CO2. After a week or so it is still doing just fine. Apparently 40 ppm does not bother the fish. I hope a lot of us start using this little gadget, so we can find any problems there might be with it.
 

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Discussion Starter · #26 ·
I'm still very pleased with mine too, but the same bubble rate entering the tank seems to take longer to change the indicator color to a good green. I can't see what, if anything, has changed, but now I get to green in mid afternoon or later, where as I recall it was early afternoon before. My indicator KH is 5 dKH too.
 

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Discussion Starter · #30 ·
I notice a very few little spots of BBA on my heater, and on one plant leaf, so even with about 30-40 ppm of CO2, BBA can still grow. The plants are doing very well though, good strong color and consistent growth.
 

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Discussion Starter · #34 ·
is the color will be the same of PH test color??

and the water inside the DROP CHECKER with KH of 4.. i do add 7 drops of PH test.. and do i've to add KH test drops?
The color will be the same as for the pH test kit, since that is what you are doing - measuring the pH of the bit of water in the bulb. It works because that water is "perfect" water for using the pH/KH/CO2 chart, unlike the tank water, which is far from "perfect". Don't add any KH test reagent to the bulb.
 

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Discussion Starter · #36 ·
OK.. im understand

SO i put 5 ml of water with KH of 4 and 7 drops of PH test.. as written in my PH test kit,

then.. i can't get this glass of drop checker.. it's not available in my country..

and till now.. i didn't find anything mach it.

could you help me?
Page 1 of this thread shows one way to DIY one. Another way is to use clear plastic tubing, about a half inch in diameter. Bend a small "U" shape. Cement a plug in one end of the "U". Attach a suction cup to the side of the "U".

Another way to DIY one: Get a piece of one inch diameter clear plastic tube, about two inches long. Cement a disk of clear plastic on one end to seal it. Make another same size disk of clear plastic, except with a half inch diameter hole in the middle. Cement that on the other end. Get a piece of half inch diameter clear plastic tube, about one inch long. Cement it in the hole, with all of the tube sticking up into the big tube. All joints have to be water tight. Attach a suction cup to the side. Put the 4 dKH distilled water and reagent in the outside, big tube. Put it in the tank with the small tube opening facing down into the water.

I'm sure there are other ways to DIY one of these.
 

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Discussion Starter · #39 ·
I did some glass blowing in college, many years ago, but I still recall it being a lot of fun. You could actually make a usable version of this that looks almost like an ADA product, just by starting with that same test tube and heating the closed end until it shrinks a bit, then blow a bubble - not too big - heat the neck and bend it, then anneal the whole thing by heating all of it and letting it slowly cool. You could then heat the open end and use a carbon rod to open it to a larger diameter. Of course you could burn yourself, the garage, the house in the process, but it would still be fun for awhile!
 

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Discussion Starter · #41 ·
Two questions people, including me, always ask are: How do you know the ppm of CO2 will be the same in the drop checker bubble and the tank water? And, how long does it take for the ppm of CO2 in the drop checker to match that in the tank water? I did some testing today to see if I could answer those questions.

I took a 2 cup measuring cup, mixed distilled water and baking soda to get about a 2dKH batch of water. Then I loaded the drop checker bubble with that water - it took 2 ml to do so. I added 4 drops of pH test reagent to the bubble. Then I installed the drop checker in the 2 cup measuring cup, with it just below the water surface. I took a length of air hose and used it to blow bubbles into the water to build up the ppm of CO2 in the measuring cup. About a minute of blowing got it to a pH of 6.5. I kept checking the pH until it rose to 6.6, which took about 30 minutes, then blew more bubbles for a minute and repeated that every 30 minutes. At various times I recorded what the pH of the drop checker water was, using the pH color chart. And, I charted the results:



You can see that the ppm of CO2 in the drop checker does equal that in the tank water, as closely as you can read the color of the test kit. And, it takes about 3 hours to reach equilibrium with the tank water. I wish it were faster in response, but 3 hours is certainly usable.
 

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Discussion Starter · #44 ·
The KH of the water in the bubble can be whatever you want to set it at. If you pick a KH of 4dKH, the bubble is green at 30 ppm of CO2. If you pick 5 dKH, the bubble is green at about 40 ppm of CO2. And, green is the most unambiguous color you can look for in the bubble, so it is best to chose the KH that goes with green at the ppm of CO2 you want to maintain. I am using 5 dKH for mine, and I'm having no problems with the fish at all. I am very tempted to try 6 dKH in the bubble, to get 45 ppm of CO2, but I haven't done so yet.

Another reason to use the KH that corresponds to green at the ppm of CO2 you want is that you then can detect ppm's that are much higher (yellow) or much lower (blue). If you used a KH where the color was yellow at the desired ppm of CO2 you couldn't tell the difference if the ppm were much higher. By that I mean, it is best to have the desired ppm give a color that is in the middle of the scale, not at one end of the scale.
 

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Discussion Starter · #46 ·
Another way to make a DIY drop checker is to use a small clear plastic bottle. Cut off the open end of the bottle, turn it over and glue it back in place upside down, so the neck extends into the rest of the bottle. Then attach a suction cup. Does anyone know what to use to glue P.E.T. plastic? It is a form of polyethylene so no glue I have found will stick well to it. I made a prototype this way using a bottled water bottle, but the joint didn't hold up at all. It works nicely though, but those bottles are really too big. I bought a 2.5 oz bottle of aloe and tried to use it but I heated it too much with hot water to clean it and the bottle suddenly shrank to a twisted mess! If that had worked it would be a $2 cost to make one.
 

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Discussion Starter · #48 ·
You're best bet for sealing that is to use heat and fuse the two parts together. Make sure the two peices are equal by careful trimming and/or sanding with the two halves jammed together. Then, heat a piece of metal on the stove or with a torch until you can just barely melt the plastic with it. I don't think there is any glue that wil stick to it for more than a few days.
Thank you Dennis. I will try that next. My grocery store had some little 2.5 ounce bottles of a hand cleaner too, but the bin was empty. That should work better than the aloe bottle, and it's $2 too. Hey, big spender!!
 

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Discussion Starter · #49 ·
Diy

I dug down deep and bought another 2.5 oz bottle of aloe to try to make a drop checker. These pictures show my progress:

First, the bottle still filled with goo, with the razor cut across the top:


After making another cut to get rid of the excess height:


After using sissors to trim the pieces:


The pieces ready to assemble:


After "welding" the bottle parts together, and attaching the suction cup, plus adding a bead of silicone to make it leak tight: (as it sits here, it is upside down - the opening will be on the bottom in the water.)


Welding isn't easy. I used a knife blade heated with a torch, using the scrap part of the bottle to judge when it was hot enough. Then I gently rubbed the joint with the hot blade to melt it together. Unfortunately, that left a couple of slight gaps which could not be sealed by any further welding. So, I used some aquarium silicone sealant to seal the entire joint.

The suction cup is installed in a hole that is melted into the side using a drill bit heated by the torch. I started small and kept going larger until the suction cup could be forced into the hole. That is a bit tricky too.

Now, you, along with me, are going to have to wait for the silicone to dry to see if this will work. (My faithful assistant, Igor, is circulating now accepting bets!)
 

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Discussion Starter · #52 ·
OK, it works! It isn't beautiful, but it works and it is dirt cheap. I had to use a bit of silicone sealant to seal the hole where the suction cup mounts, but once that cured for a couple of hours it has been water and air tight. It took about 2 1/2 hours to reach the same green color as my ADA style drop checker. Here they both are, in the tank - still green with GDA for another day.


 

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Discussion Starter · #55 ·
Yes, I have GDA in the last throes of its life cycle. If all goes according to plan I will be wiping it off today.

Fome, KH test kits are very cheap and very useful, unlike many other test kits. Aquarium Water Testing: Aquarium Pharmaceuticals GH/KH Test Kit I don't know any reliable method for making water with a specific KH other than testing and retesting, and even that can be difficult.
 
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