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How to check your drop checker....

True that the co2 art fluid does give a better reading when used against a white background and probably doesn't need the extra bromo when used in that situation. I also use a PH pen to keep a eye on how much ph drop I am getting, still hard to say it collaborated 100% accurately.
 
And to confuse matters even more there are actually two types of bromothymol blue. Protonated and De-protonated.

De-protonated appears as a blue liquid before adding to ?dKH water.

Protonated appears as a red liquid before adding to ?dKH water. (Looks red in the bottle but is actually concentrated yellow and stains yellow on a blot test).

I put ?KH above because they act the same way no matter the KH of the stock solution water. I have done side by side tests using the same KH of water, the standard 4dKH and my tank dKH which at the time was dKH9. The water I used at 9dKH was my water change water before adding GH salts, it is reconstituted RO/DI using KHCO3 at 8.1g per 25L, the reason for doing this is that according to the ph/KH/CO₂ chart the curve is quite flat here and so the colour change is more gradual and more accurate than a lower KH which indicates in a narrower window.

I found that regardless of the dKH of the stock water solution Protonated Bromothymol blue will indicate 30ppm CO₂ well before the De-Protonated does if the advice you are following is a green drop checker meaning 30ppm CO₂. If this is the advice you are following then with Protonated indicator you will be underdosing CO₂. If you go by a yellow dropchecker for 30ppm CO₂ using De-Protonated indicator for 30ppm then you're overdosing CO₂.

If using Protonated Bromothymol Blue you want a yellow dropchecker for 30ppm.

If using De-Protonated Bromothymol Blue you want a green dropchecker for 30ppm.

27663991240_f73cdef96e_z_d.jpg


Both the dropcheckers on the left were photographed immediately after removing them from the tank, the checker on the right is a control which never went in the tank and is the colour for atmosphere equilibrium (both liquids indicate this colour for atmosphere equilibrium when added to whatever dKH water). Dosage for the indicators was at 3 drops per 5ml of dKH water, this test pic was 4dKH stock solution. The differing size of the dropchekers above made no difference when compared to a later test using both same sized dropchekers (not photographed), the reaction was the same.

Using a lower concentration of indicator say one drop per 5ml narrows the inaccuracy window but makes it very hard to read.
 
X3NiTH said:
And to confuse matters even more there are actually two types of bromothymol blue. Protonated and De-protonated.

De-protonated appears as a blue liquid before adding to ?dKH water.

Protonated appears as a red liquid before adding to ?dKH water. (Looks red in the bottle but is actually concentrated yellow and stains yellow on a blot test).

I put ?KH above because they act the same way no matter the KH of the stock solution water. I have done side by side tests using the same KH of water, the standard 4dKH and my tank dKH which at the time was dKH9. The water I used at 9dKH was my water change water before adding GH salts, it is reconstituted RO/DI using KHCO3 at 8.1g per 25L, the reason for doing this is that according to the ph/KH/CO₂ chart the curve is quite flat here and so the colour change is more gradual and more accurate than a lower KH which indicates in a narrower window.

I found that regardless of the dKH of the stock water solution Protonated Bromothymol blue will indicate 30ppm CO₂ well before the De-Protonated does if the advice you are following is a green drop checker meaning 30ppm CO₂. If this is the advice you are following then with Protonated indicator you will be underdosing CO₂. If you go by a yellow dropchecker for 30ppm CO₂ using De-Protonated indicator for 30ppm then you're overdosing CO₂.

If using Protonated Bromothymol Blue you want a yellow dropchecker for 30ppm.

If using De-Protonated Bromothymol Blue you want a green dropchecker for 30ppm.

27663991240_f73cdef96e_z_d.jpg


Both the dropcheckers on the left were photographed immediately after removing them from the tank, the checker on the right is a control which never went in the tank and is the colour for atmosphere equilibrium (both liquids indicate this colour for atmosphere equilibrium when added to whatever dKH water). Dosage for the indicators was at 3 drops per 5ml of dKH water, this test pic was 4dKH stock solution. The differing size of the dropchekers above made no difference when compared to a later test using both same sized dropchekers (not photographed), the reaction was the same.

Using a lower concentration of indicator say one drop per 5ml narrows the inaccuracy window but makes it very hard to read.
Click to expand...

Interesting! Thanks for that post, the Bromothymol blue I had been adding to the co2art pre mixed checker fluid was the red Protonated but I have no idea what Bromothymol blue they originally mixed to make the solution, I should really make up my own dKH water then add the red Protonated Bromothymol blue, reading your post above am I understanding this correctly... you are saying it doesn't matter what dKH of the stock water solution is? So I could just use distilled water in my checker then add the red Protonated Bromothymol blue rather then trying to create 4dKH water?
 
Don't think that would work. Distilled water tends to absorb co2 from the atmosphere and will probably go yellow out of the tank.

Sent from my STH100-2 using Tapatalk
 
AverageWhiteBloke said:
Don't think that would work. Distilled water tends to absorb co2 from the atmosphere and will probably go yellow out of the tank
Click to expand...
Yes distilled water will take up CO2 from atmosphere but only until in equilibrium with the 400ppm present in air. You use Henry's law (I thinks that the one) to work out the ppm in water based on partial pressures, which if I remember correctly give 0.6ppm. 0.6ppm won't have any effect on your indicator.
 
Hi all,
AverageWhiteBloke said:
I didn't actually realise that Bromo Blue was slightly acidic, one would assume that anything that measures PH should be neutral.
Click to expand...
You can ignore the acid bit.

If you make it up from scratch you start with the sodium salt of bromothymol blue, and you add a very small amount to DI water, (it is something like 0.5g of the salt made up to one litre), and that makes a really dark blue solution.

I assume this is because sodium (Na) is an alkali metal, so the sodium bromothymol blue solution is blue. Presumably by the time you've added a couple of drops of indicator to the 4dKH solution it really doesn't make any difference to the pH.
X3NiTH said:
De-protonated appears as a blue liquid before adding to ?dKH water. Protonated appears as a red liquid before adding to ?dKH water. (Looks red in the bottle but is actually concentrated yellow and stains yellow on a blot test).
Click to expand...
I think the protonated - deprotonated bit is actually the pH change.

Deprotonated is at a pH above pH7.6 (conjugated base), and the indicator is blue, when you add an acid (defined as a "proton donor") in solution the indicator becomes protonated (it has accepted a proton) and the color changes to yellow (conjugated acid).

In the bottle it is a concentrated solution of the conjugated (protonated) acid and appears darker and more red (just like yellow food dye)). I assume if you start with bromothymol blue (not the sodium salt) you end up with the protonated yellow solution, via the dissolution of CO2 (but it is still a weak acid).

When you are at ~pH7 you have a mixture of protonated (yellow) acid and deprotonated (blue) base, and yellow and blue make green.

There is an explanation (with the chemistry) at <"The acidic form of .....">.

cheers Darrel
 
ian_m said:
Yes distilled water will take up CO2 from atmosphere but only until in equilibrium with the 400ppm present in air. You use Henry's law (I thinks that the one) to work out the ppm in water based on partial pressures, which if I remember correctly give 0.6ppm. 0.6ppm won't have any effect on your indicator.
Click to expand...

OK, back back in the day before stumbling across this board and before much info was available I use an API de-ioniser resin and thought it would be a good idea to use de-ion water in the DC as I had heard about tank water affecting the measure. The fluid pretty much turned yellow although thinking about it that was probably because I was injecting co2 and it wouldn't take much to turn yellow I guess with de-io water. I think I also tested my WC water after de-ionising it before going in the tank for PH and that was also very acidic.
 
ian_m said:
However since moving to the JBL one...brilliant. Its plastic so if dropped doesn't break and it has a white piece of plastic inside which makes reading the colour in the tank easy, no faffing with white plastic sheets. Easy to clean as well, pull apart wash in sink and easily push back together.
Click to expand...

A problem with the JBL DC is that, if a film of organic (or any other) material develops at its interface with the tank water, it can't be seen. And that can lead to misleading CO2 indication. That's a problem that I had with the JBL DC that I own. The 'white' piece of plastic also discolours over time.
 
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X3NiTH said:
The water I used at 9dKH was my water change water before adding GH salts, it is reconstituted RO/DI using KHCO3 at 8.1g per 25L...
Click to expand...

Hi X3NiTH,

I don't have access to potassium bicarbonate. Would sodium bicarbonate be OK? And, if I understand you rightly, does this result in 9dKH?

JPC
 
What is it you're trying to do Jay?
 
Ahh ok mate. To be fair I think the only important bit is the "bi-carbonate" as long as the solution is 4KH doesn't really matter. They sell potassium bicarbonate on ebay, I get some for raising my very soft tank water. 4KH solutions are so cheap though so hardly worth diy'ng them I find. Are you having some problems with yours or something?
 
I used Potassium Bicarbonate in the drop checker mainly because I had it but also because the plants would enjoy the extra potassium more if the drop checker accidentally fell from the tank wall and disgorged its contents into the water column (yeah I've done that before).

:)
 
I have a question if you don't mind please, my jbl permanent drop checker co2 plus test kit....
https://www.pro-shrimp.co.uk/water-...weIM_Gu3lkCWA58yT2-4tMy9RJlxZEMIaAu7AEALw_wcB
Is a fluid that doesn't require mixing with tank water etc... Just 35 drops in the checker.it says takes upto 2 hrs to change colour so I have my co2 come on 2hrs before lights on and co2 is running for 8 hrs and photoperiod which is 7 hrs long. After 2 hrs the checker is still blue, after 3 hrs it's changing to green and by 4 hrs is pretty much moss green. 5 hrs it's changing to lime green and 6 hrs until co2 off its consistently lime green. How soon should it be lime green? If I up the co2 to get it lime sooner then by 6hrs of injection I'll be over shooting. Thanks in advance.
 
Have you verified your drop checker works, by doing the breath test as in the first post in this thread ? Just to verify the indicator solution is working.

See this thread for the maths of how CO2 concentration varies with time.
https://www.ukaps.org/forum/threads/co2-concentration-versus-time-the-maths.51423/

So to get drop checker green at lights on..

- You need to increase your in injection rate as well as increase surface agitation. Injection rate roughly controls how quickly its gets to green and surface agitation increases loss rate which limits the maximum CO2.

- Leave injection rate the same, but decrease the loss due surface agitation and/or cr*p CO2 injection method.

You haven't told us your tank size and CO2 injection method.

I had great difficulty getting green drop checker (all over then tank) at lights on using an in tank diffuser, but as soon as I switched to inline diffuser and didn't change injection rate BANG yellow drop checker, fish gasping...oops.

It will take a while to get injection rate, CO2 loss rate adjusted so that drop checker is nicely green at lights on.
upload_2019-1-8_9-10-43.png
:D
 
It's a 70 litre tank quite heavily planted with the fluval u3 filter I use the integrated spray bar for under water flow. The glass ceramic diffuser is situated at the outflow and blown about the aquarium. Drop checker works as it changes colour throughout the injection period and Sunday I refilled with new fluid. I'm already on 2 bps and it's only 70 litre
 
Ceramic glass diffuser wont help, not the most efficient was of injecting CO2.

Try increasing the CO2 rate and angling the spray bar upwards a bit.
 
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