DIY Drop Checker

273570 Views 357 Replies 80 Participants Last post by HeyPK, Jun 9, 2011

hoppycalif

Discussion Starter · Oct 12, 2006

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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hoppycalif

Discussion Starter · #41 · Nov 6, 2006

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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graedog

· #42 · Nov 6, 2006

Thanks

Just a quick thank you

I found this post really interesting and helpful

Graeme

swifty1

· #43 · Nov 6, 2006

Great post! - I've ordered 2 drop checkers, one amano style, one pear shaped, but one question - should the KH in the bubble be the same as the KH of the tank water?

or should it be worked out to give a green colour with the ppm level I'm seeking?

I think its the latter?

hoppycalif

Discussion Starter · #44 · Nov 6, 2006

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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swifty1

· #45 · Nov 6, 2006

That's nice and clear Hoppy - thanks!

Just waiting for my drop-checkers now!

hoppycalif

Discussion Starter · #46 · Nov 6, 2006

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.

dennis

· #47 · Nov 6, 2006

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.

hoppycalif

Discussion Starter · #48 · Nov 6, 2006

dennis said:
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!!

hoppycalif

Discussion Starter · #49 · Nov 7, 2006

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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dennis

· #50 · Nov 7, 2006

The weak part to this may be the hole for the suction cup. Hopefully though, the rubber will swell slightly when wet and prevent any leakage. The silicone may not stick very well but if it is only for small holes it will probably be OK. In hindsight, a way or heat crimping the joint may be best, similar to the way they seal those damn packages for portable electronics. Heated pliers may do the trick.....

kamel_007

· #51 · Nov 7, 2006

hoppycalif said:
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!)

Looking forward to see i t working!

hoppycalif

Discussion Starter · #52 · Nov 8, 2006

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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Fome

· #53 · Nov 8, 2006

I've an odd request.

I do not have a KH test kit. Is there any way you could "estimate" how much baking soda it would take to reach KH of 4.0 in a certain volume of DI water? ie. a cup, 100 ml, etc.

As I understand, it's not extremely important to get exact values on co2, just estimates on if your plants are getting enough and your fish aren't in imminent danger.

I plan on making one of these soon!
I already have sealant, suction cup, ph indicator fluid, and an adequate bottle.
Except for the DI water, this'll be one of the few parts of my tank that cost me nearly nothing!

Appreciated!

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kamel_007

· #54 · Nov 8, 2006

hoppycalif said:
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.

Your tank glass look's like green!

DO you've an algea bloom?

hoppycalif

Discussion Starter · #55 · Nov 8, 2006

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.

dennis

· #56 · Nov 8, 2006

If I have done the math correctly, trust me, I probably did not....

Using NaH2CO3 to get 5degrees requires 75.18mg in 1 liter of RO/DI water.

For comparison, a penny weights 2.6 grams or 2600mg.

Anway, if you buy a 1 gallon jug of RO/DI (3.79liter/gallon) you need to add 284.9mg or .285g NaH2CO3. The only way to accurately measure this is to use a gram scale.

bpimm

· #57 · Nov 8, 2006

Another way to weld the plastic bottle is to use a cheap soldering iron, the lower the wattage the better. Then you can use the extra bottle material cut in strips for welding rod to fill in the gaps.

I have used a variac to control the heat of the soldering iron. you may be able to use a dimmer to turn it down a bit also.

hoppycalif

Discussion Starter · #58 · Nov 8, 2006

bpimm said:
Another way to weld the plastic bottle is to use a cheap soldering iron, the lower the wattage the better. Then you can use the extra bottle material cut in strips for welding rod to fill in the gaps.

I have used a variac to control the heat of the soldering iron. you may be able to use a dimmer to turn it down a bit also.

When I moved last year and got rid of my workshop tools I apparently also got rid of my soldering gun and iron. In any case I couldn't find them. I suspect that they would be much too hot for PET plastic - there seems to be a narrow temperature band when the stuff welds and doesn't char. Don't even the cheap soldering irons have a temperature control of some kind built in? If so, how would dropping the voltage affect the temperature?

The DIY drop checker was still working this morning, with no leaks that I can detect. It finally worked loose from the glass, probably due to the GDA on the glass, and began floating around the tank. So, I removed it at noon - I consider it to be a success!

bpimm

· #59 · Nov 8, 2006

hoppycalif said:
When I moved last year and got rid of my workshop tools I apparently also got rid of my soldering gun and iron. In any case I couldn't find them. I suspect that they would be much too hot for PET plastic - there seems to be a narrow temperature band when the stuff welds and doesn't char. Don't even the cheap soldering irons have a temperature control of some kind built in? If so, how would dropping the voltage affect the temperature?

The cheap ones are not thermally controlled, That's why I used the Variac to control the temp. a variac is a variable transformer so it just lowers the voltage. a soldering iron is a resistive load just like a light bulb, so a standard dimmer may work to do the job as long as the wattage of the soldering iron is within the rated wattage of the dimmer.

dennis

· #60 · Nov 9, 2006

Here is my contribution to the DIY drop checker:

Took me about 15 m inutes and a Benzomatic torch. Truth be told though, I have been dinking around with this for a few days and this is my 5th attempt. Not great but functional and fun to do. I never considered heating and actually blowing the end until hoppy suggested it. Also, you'll notice the end is broken, apparently a screw driver is not a substitute for a carbon rod to flare the end. After it broke I did heat the end so it is not sharp and the fishies are safe. This may turn out ok though as it broke at a real angle meaning that the water interface is a little larger than it would be otherwise. kH is 4.2 (Lamotte-80ppm) and solution has about 4 drops of indicator from the AP pH test kit.

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