Co2 Indictors

[scottward]

Hi. I have a Red Sea CO2 pro kit. I have the indicator attached to the glass at the opposite end of the tank. Are these things any good? Are they really just pH testers?

 

[smithrc]

Hi. I have a Red Sea CO2 pro kit. I have the indicator attached to the glass at the opposite end of the tank. Are these things any good? Are they really just pH testers?

Thats exactly what they are...

There is a complicated background to them - but yes - they work by monitoring the PH of teh test solution - the PH will change depending on the amount of CO2 in the air trapped between the test solution and the tank water. This then reflects the amount of C02 in the tank water.

have you used tank water in the test solution?

From what I understad it is better to mix up an RO water sample so that it has a KH of 4 - then use that - that allows you to know what colour the co2 test kit will be at a certain co2 content - eg 30ppm CO2 in water with a KH of 4 the PH will be 7.0 (I think thats right).

 

[nicklfire]

Honestly i've found that makingi the stuff isnt as reliable as just buying a bottle that will last you a years. You can fiddle around with making the stuff but it's a chemistry project.. if your wrong you dont really know all that much. Spare the 8$ and just buy some... it's cheap and reliable and lab tested.

Why do you have to get that 4dkh solution you ask well if you just use your tank water then there are too many other variables in your tank water to actually give you a proper accurate test result.

me personally i've used the red sea one, i dont like the look of it and it only contains a very little amount to add... buy a bigger co2 drop checker, ebay has tons.

 

[scottward]

So does that mean if the 'CO2 Indicator' reagent runs out I can use normal pH test drops?

If I were (hypothetically) to drop the pH of my tank by adding pH down, wouldn't this make the CO2 indicator go yellow even though I haven't added any CO2?

Scott.

 

[nicklfire]

Yea if it's the stuff that turns blue and green and yellow then yes.. think it's called... Bromothymol blue.
and if you were hypathically add ph down or up in that case it would overall affect the co2 drop checker. would actually turn blue if it went down.. but besides the fact.. It's changing qualities in the water. (please someone let me know if i'm wrong in this case) They are 2 qualities that are linked together, change one quality then you'll get a difference on the other one, such as ph swings during night when co2 goes off.. or on for that matter, but pH buffers replace KH therefore rendering the reading as useless

so to answer your question if you were hypothetically to use the ph down or up as a buffer it will change your readings.. but your as i said again.. ph buffers replace kh which make your readings useless...so you cannot adjust those water qualities to gain co2.

take a read on the pinned co2 forum, you might get a bit more technical in there, maybe a bit to clarify things.

 

[George Farmer]

If I were (hypothetically) to drop the pH of my tank by adding pH down, wouldn't this make the CO2 indicator go yellow even though I haven't added any CO2?

Scott.

No.

The pH of the solution in the CO2 indicator is exclusive to the tank water because of the air gap between the tank water and the CO2 indicator solution.

The CO2 gas that transfers from the tank water to the tester, through this air gap, alters the pH, thus giving you an accurate reading without other pH influences i.e. humic and nitric acids.

At 30ppm the pH is 6.6 in a 4dKH ref. solution is a distinct green colour, like a lime.

 

[scottward]

The instructions say to fill the indicator with 1 ml of water and add 2 drops of reagent. It's pretty clear to me now that the chemistry of the water used to fill the indicator is important.

Should I fill the indicator with distilled water?

 

[nicklfire]

i guess i stand corrected than