One place is http://www.aquaticplantcentral.com/f...-checkers.html, where the 4 dKH solution is included, premixed with pH reagent (bromothymol blue). You could email that seller to ask about buying just the solution.

Here is a place to buy the 4dKH water. http://www.aquaticplantcentral.com/f...standards.html. You could email the seller and ask if he sells it premixed with pH indicator reagent.

Just received a drop checker I purchased on eBay. The glass type with the bell, and bulb at the other end.

The instructions read:

How to use it :
1. Fill the checker bulb with 2/3 of distill water then add 3 to 5 drops of indicator solution to blue color
2. Careful put the drop checker about 3 inches under the water level.
3. After a couple of hours, you can match the color of the indicator solution with the test card


The distilled water only turns amber/yellow as is the color of the regent.
Contacted seller buy insists it should turn blue.

Does anyone have any idea why it doesn't turn blue?

I tried using 4gKH water but only turns the water yellow.



PS: Seller now says this is a new regent, that it is supposed to be amber and not blue. I don't feel comfortable with this answer and his not knowing what color his product should be

That new reagent sounds suspect to me, ditch it! Pick up a new PH test kit and use 2 drops of it's reagent in your DC in which you should have 4KH solution, you cannot use just DI water in your DC.

If you do not have a ref 4KH solution reach out to the guy or gal here for a 500ml bottle which will easily last for almost 2 years and thats factoring changing the DC weekly.

Thanks for reply.
I was wrecking my mind with this, but doubting my understanding on the subject which is as you concur.

I ordered 4 bottles of regent and each with the same result: amber/yellow and does not change color in the tank. The tank has, at least, 19ppm CO2.

Is it allowed in this forum to warn other by giving out the name?

raul

Thanks for reply.
I was wrecking my mind with this, but doubting my understanding on the subject which is as you concur.

I ordered 4 bottles of regent and each with the same result: amber/yellow and does not change color in the tank. The tank has, at least, 19ppm CO2.

Is it allowed in this forum to warn other by giving out the name?

raul

PS Here is a picture of the DC 6 hrs in the tank.

Thanks for reply.
I was wrecking my mind with this, but doubting my understanding on the subject which is as you concur.

I ordered 4 bottles of regent and each with the same result: amber/yellow and does not change color in the tank. The tank has, at least, 19ppm CO2.

Is it allowed in this forum to warn other by giving out the name?

raul

While I wait for my certified 4dKH I have made my own batch using kitchen measuring utensils and TB's instructions.
It turned out over 4dKH so I added distilled water and tested, distilled water and tested again until it tested out 4dKH.
How accurate is this?

I am using it in my DC and it's looking good by using regent from an API PH test kit. Three drops regent + my 4dKH.
First it turned blue and after about 4 hrs turned green.

There is no reason not to make your own 4 dKH water, provided you use distilled or deionized water, and have a good KH test kit. Since the measured ppm of CO2 is directly proportional to the KH of the drop checker water, even a 20% error in KH still gives a more accurate CO2 measurement than trying to do it with tank water KH and pH. I find it extremely difficult to arrive at 4 dKH water when trying to make it myself - I usually go through a half gallon of water before finally getting close. That's why I gave up the DIY method.

.......X 2

Tks for reply.

Actually I know that the 4dKH I was able to make was pure luck.
I just poured some distilled, without measuring, and it tested out 4dKH !
Don't know if I'll be able to do it again but, I'll see when I run out of my present supply.

As to the accuracy of my PH test kit, it's Aq. Pharmaceuticals. Is this considered a good test?