Drop Checker

[MyanRan]

Just a quick question. I was reading that when the drop checker is green that means there is about 30 ppm of CO2 in the water. Means the pH is 6.6? Is that the pH of the water to? I was confused because the article said that the pH is of the air? Confused

 

[DanTheGuppyMan]

That question was confusing LOL....I'm not sure, my drop checker is green and my pH is between 6.6-6.8 and I think pH is in the water...not air...lol but whatever I may be wrong haha. But yes- green is supposed to have around 30ppm which is what you are shooting for, blue is too low and hello is too high.

 

[MyanRan]

Thanks! I don't know what the air part was... Haha. One last question, if I am not even dosing co2, will this still tell me how much co2 is in my water?

 

[fort384]

If you are not injecting CO2 and your tank is open to the air (even if it has a lid) the CO2 is going to be at equilibrium with the air in your house - normally around 7ppm.

A drop checker is indirectly measuring the quantity of CO2 in the water. It is measuring the pH of the solution in the drop checker, not the air. The pH inside the drop checker may or may not be the same as that in your tank - it depends on if you are using tank water in the drop checker, or if you are using a reference solution of 4 degrees KH, which is the recommended method to get the most accurate reading.

 

[DanTheGuppyMan]

Getting a drop checker and not even injecting CO2 in your tank, whether it be pressurized or DIY seems like a waste of money...and what fort means is you use the 4dKH solution in the checker, add a few of the pH test drops and It uses that solution to measure the CO2 in your water, if when put together that makes sense lol.

 

[MyanRan]

I would be injecting CO2 eventually, and wait... So it's giving you the pH of what when you use 4dKH solution?

 

[fort384]

The pH of the 4dKH solution. Co2 is acidic and lowers pH. We know the value of the pH of a standard solution at incremental levels of co2 so as the pH of the liquid in the drop checker changes we can tell approximately how much co2 we have in the tank.

 

[MyanRan]

Thanks, that makes sense.

 

[phin]

What kind of error are we looking at with DIY dkh test solutions? I've got a gallon of distilled water on hand, a pH test kit, KH test kit, digital scale to the 0.1 g. I'd rather not make 5L of 40dkh solution and then dilute.

If I was to make 500mL of 4dkh solution based on adding a small amount of baking soda, test KH, test pH, add more as needed.... By doing it this way I could estimate a 4 dkh solution pretty easily. I mean, effectively, the drop checker goes blue, green, dark green, yellow - it doesn't seem exactly precise, more of a range of CO2 concentration - Low, Good, High.

So again, I ask, how precise do you have to be to make the 4 dkh solution?

btw, I intend on making a drop checker from a vinyl hose & nailpolish jar, seems pretty simple.

 

[fort384]

The problem is it is such a small change in KH that effects the level of co2. But like you said it is all kind of an estimate anyway so if you can make 500mL and get it to test reasonably close to 4dkh it is still better than using aquarium water.

 

[aqua_chem]

There is probably fairly significant error in the KH test, but whenever you're measuring something (co2 in this case), your final measurement is only as good as your weakest step, and the weakest step in this process isn't the measurement of dKH, but rather interpreting the color of the drop checker. Green vs light green vs dark green vs yellowish green... It's all really subjective and not well quantified in the slightest other than green is good, lighter shades are more than normal green, and yellow is too much.

If you like, you can measure two 5 mL aliquots, combine them, and measure that such that each drop will be .5 dKH. That should milk a little more precision out of the measurement.

 

[fort384]

That is what I do when I make 4 dKH solution - I double the starting amount of test liquid, so that it increase the resolution of the test kit. Of course, I was also selling it on eBay so wanted to make it as accurate as possible for "customers". If I was making it for myself, close would be good enough.

 

[phin]

I made some 4 dkh last night. I started with 500ml distilled water. Added .5g of baking soda. Tested the KH and it was somewhere between 25 & 30 degrees. (I got tired of going drop by drop at 20 and added 10 at once.) I diluted 10ml of that solution with 75ml of distilled water. That gave me a solution with 6-7 dkh. I diluted again with 50ml of distilled. That gave me a solution that turned yellow on the 4th drop of KH test regent. pH tested in at 7.6 on both the low-range pH test and high range (slightly past 7.4 on the high range kit).

After testing the solution and filling my drop checker I have a tad over 100ml of 4dkh left.

I made a drop checker from a small vial of children's nail polish, standard airline tubing, teflon tape, 3/8" ID vinyl tubing and a small suction cup. I cleaned the nail polish jar with alcohol, sulfamic acid, & a good hot water rinse - then a soak in prime for a min.

I wrapped the airline tubing that would be touching the inside neck of the vial in teflon tape to make a snug seal and pushed the tubing into the jar, leaving about 1/8" poking out. I took the larger length of vinyl tubing, cut it to about 1.5" long. I cut a small hole with a razor blade about 1/3 of the way from one end (bottom) and pushed the nipple of the suction cup in. I then pushed the top end of the tubing over the outside of the vial, around the glass threads where the nail polish cap would fit.

I filled the chamber of the vial about half way up with 4dkh solution from a 5ml test tube that had 6 drops of pH indicator solution. when filled with solution and turned upside down, so the bottom of the vial is up, the blue dkh solution sits nicely around the airline tubing in the chamber with a air pocket above the blue solution and an open airway down the airline tubing out the neck of the vial. I then fixed the drop checker to the inside glass of the tank.

I was afraid I did something wrong, as for an hour I didn't get much change in the color. The lights were on the 8th hour for the day, so the photoperiod was ending, CO2 was on, and in that hour the color went from dark blue to "regular" blue. However, today when I woke up the color had changed to some shade of green. It was hard to tell as the lights were out in the tank, but I'll see this evening when I get home.

Sorry for the hijack, I just figured a description of my construction of a drop checker might be helpful for some.

 

[fort384]

Great! Can you post a pic?

 

[phin]

I'll try and get one up tomorrow. I've still got some pics of my (what I think are) micro swords I need to post as well.

 

[phin]

so based on my drop checker, with 4dkh solution, it appears my pH is somewhere around 6.4-6.6, so that would estimate my CO2 concentration to be 38ppm +/- 10ppm?

 

[fort384]

Yup. Looks good.

 

[phin]

Yup. Looks good.

Thanks. So its not too high? what would be a potentially dangerous level for CO2?

 

[fort384]

Over 50 and you might start to see some issues. I prefer 30-40 though a lot of folks recommend 20-30.

 

[phin]

Excellent, thanks. So far all the inhabitants look to be doing fine at the current CO2 concentration.