Hi all!

I got a Red Sea CO2 Indicator today as part of the CO2 kit they sell. I set it up and put it in the aquarium but the problem is, even after the 10 minutes they say it needs to read the CO2 in the tank, the indicator is still yellow (too much CO2).

I haven't even started injecting CO2 into the tank yet, so I can't imagine that I have too much of it. Up to now I have been dosing Flourish Excel, but I don't think that would cause this reading either?

I've tried using the KH/PH chart to figure out CO2 levels also, but I have a large piece of driftwood in the tank which is lowering pH, and I'm not sure if that nullifies the accuracy of the chart?

For reference:
kH = 2 degrees
pH = 6 (or lower, test kit only goes to 6)

Can anyone help me figure this out? Thanks!!

Is the solution yellow from the bottle? It takes hours for the reading to equilibrate, not 10 minutes...just keep waiting.

Yea the solution is yellow from the bottle. Ok I didn't know it took hours, the manual that came with it said 10 minutes Thanks alot!

are you using a KH4 solution in your indicator? I mixed up a batch of KH4 and KH5 and my Red Sea indicator is working fine. Maybe the KH2 of your water is just indicating a high CO2 level becuause you KH is so low.

With a KH of 2 you would be yellow way lower than you want to see. Obviously since you aren't injecting CO2 yet you can't be more than 3 ppm and already turning yellow. I just got one of these and took a bit of time to make a KH 4 solution. After I put it in the tank it took about 2 hours to turn colors.

At the bottom of the GB Introduction page, the instructions for the Red Sea CO2 Indicator say: "Note the CO2 indicator will give incorrect readings if the °KH drops below 4°."

Ah, that would be why...it's still reading yellow after this time. So how would I go about making a kH4 solution? Baking soda?

On that note, is a kH of 2 something I should be worried about? Should I try to raise it?

Thanks!

Hoppy and billonzz have posted the directions on how to make a 4° and a 5° KH solution.

Also, billonzz is selling various 4° and 5° KH solutions.

I dont understand Red Sea. If from what I have read is correct, its the KH that sets what co2 level the indicator will be green (30ppm w/KH=4, 40ppm w/KH=5) etc. So why do they just indicate problem with accuracy with KH under 4? What about over 4? And also they should stress the importance of using something like distilled water or RO water, since tap water and tank water both can have other buffers present. I also like the idea of dilluting the KH solution 50% so you can measure in .5 degree increments rather than 1 degree.

I'm sorry Left C, could you link to the directions for the 4 KH solution? I did a search and couldn't find it.

Thanks!

I sure will.

Hoppy - drop checker intro: https://www.plantedtank.net/forums/ge...technique.html

billionzz's KH standards for sale: https://www.plantedtank.net/forums/sw...tml#post389457

billionzz's how to make them: https://www.plantedtank.net/forums/ge...ndard-how.html

There's many posts about drop checkers. Just search for drop checker and you can find them.

Those are good questions, loaches.

It doesn't say anything in the instructions about a KH above 4° not being accurate or why it isn't accurate below 4°. I would think that if the indicator fluid is a good quality Bromothymol Blue solution and you make a KH solution of either 4° or 5° KH with distilled/RO water and an almost pure carbonate buffer that it should work. I wonder if they are saying that it is not accurate under a KH of 4° because of interference from the other buffers and acids in the aquarium. If it's crappy indicator solution; well, that's another animal.

The instructions tell us to use aquarium water, but we know better from Barr's, Hoppy's, billlionzz's and other people's work with it.

Also, at the end of the instructions, it says: "Note: Replace Indicator Liquid after every water change or at least once a month."

I have two of the Red Sea Indicator's but I haven't made my KH solution yet. I have everything that I need to make it but I've been doing some spring cleaning and I haven't gotten a round toit yet. If the indicator solution is crappy, I have some other Bromothymol Blue solution here as well.

Have you tried LaMotte's Alkalinity test kit? It gives you a rather abrupt endpoint of purple. It's a green color before you reach the endpoint and it turns a reddish orange color if you go past the endpoint. But, there were some issues about the accuracy of the markings on the test bottle awhile back.

So I have the opposite problem. I put the Red Sea CO2 indicator drops in the aquarium water and the solution turn immediately blue. I tried water from the tap, and its the same thing. I have well water with water softener. Humm...

you need 4dkh solution. Not tap water. Not tank water. 4 dkh solution.

So I made a 4dkh solution as per instructions from Hoppi. If I put two the two Red Sea CO2 indicator drops prescribed, what color is the solution supposed to turn?