Old 4dkh solution, starts out green - The Planted Tank Forum
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post #1 of 4 (permalink) Old 05-03-2013, 02:18 AM Thread Starter
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Old 4dkh solution, starts out green

At least two years ago I made my own 4dkh solution using baking soda, distilled water, and a milligram scale. Not too long after I broke my drop checker and was too lazy to order a new one.

I'm getting more involved in my aquarium again and have finally acquired a new drop checker. I still have the same 4dkh solution that's been stored in a glass jar with a metal lid on pretty tight. I've tested it and it still registers as 4dkh.

However, when I add my bromothymol blue to it, I get a green color. I thought maybe there's just some dissolved gasses in there somehow messing things up and let some of the solution sit out in a shot glass for a few hours. Sure enough, it's now blue.

I guess my question is, is this anything to be concerned about? Does it matter if I don't let it sit out before adding it to the drop checker? Should I let the whole jar sit for a day or so with the top off to let it reach an equilibrium with the atmosphere again? Searching around, I haven't been able to find anyone else ever having this problem.

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post #2 of 4 (permalink) Old 05-03-2013, 02:46 AM
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Only thing I can think of is the microorganisms and such that were locked in the container used all of the oxygen and exhaled carbon dioxide which made the water full of dissolved Co2 which is why your solution went green. Then when you poured it into a shot glass and let it sit oxygen was diffused into the solution and turned it blue. I personally say it's fine.

Just my $0.02

Originally Posted by CapnRon
Well if you're going to be a noob I guess you should go all out........
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post #3 of 4 (permalink) Old 05-03-2013, 02:13 PM
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If you let it sit uncovered, you will get evaporation, thus throwing off the dkH.

Did you shake it up really good before your tests?
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post #4 of 4 (permalink) Old 05-03-2013, 03:25 PM
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same thing happened to me with my freshly made 4dKH sol'n. I'm on board with Aulo - I think it sitting sealed up for a while traps gasses or something. Once mine sat in the drop checker for a few hours, it was reading fine. (I had postponed turning on my co2 until I knew my checker was reading correctly, and it went from freshly-mixed green to blue after sitting for a few hrs).
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