[Cardinals]

pH vs KH

If you read carefully, Chuck Gadd notes in his discussion that the equation is not valid for water that isn't "perfect".

Is it possible to have an planted tank pH 7 @ 6dKH without supplemental CO2 or non carbonate buffers (e.g. phosphates)? According to the chart CO2 would be ~18ppm, well above normal equilibrium values of 0-5ppm

 

[qwiksilvertrav]

I found these charts to be pretty inaccurate. I used it just before getting a drop checker and had a PH of 6.6 and a KH of 6.5 telling me I had over 70 ppm of Co2.

I then put in the drop checker and it read a slightly dark green which is about 20ppm of Co2. I turned up the Co2 a little bit and got it at 30 - 40 (lighter green) and boom the plants started pearling like crazy. Other tests have indicated this chart not reading out how my drop checker is reading. I trust my drop checker over this personally.

 

[Cardinals]

I found these charts to be pretty inaccurate. I used it just before getting a drop checker and had a PH of 6.6 and a KH of 6.5 telling me I had over 70 ppm of Co2.
I trust my drop checker over this personally.

If I've looked at the chart right, pH 6.6 dKH 6.5 equals 49ppm CO2?
Doesn't a "drop checker" actually measure the pH (using bromothymol blue), not CO2. CO2 is then deduced from the chart according to your KH?
If your "drop checker" is green, using bromothymol blue, pH is ~6.6. Therefore, if your dKH is still 6.5 your CO2 is ~49ppm. However, if you have reduced your dKH to 4, then CO2 ~30ppm. (using the charts)
If you are interested, I am using excellent LaMotte CO2 titrator which could be used to verify your tanks parameters.
:fish1:

 

[Hoppy]

The whole point of using a drop checker is to make the CO2 chart work. It doesn't work when used with typical aquarium water, because there are too many things in the water that affect the pH, other than just carbonates and CO2. With a drop checker you are measuring the pH of a tiny bit of water that contains nothing affecting pH except carbonates (bicarbonates) and the CO2 that equalizes between the drop checker water and the tank water. The La Motte CO2 test is also a pH/KH test, so is also inaccurate. But, you can buy a CO2 probe and meter that will very accurately measure the CO2 concentration in the tank water, and do it very fast. All you need is a couple thousand dollars to spare.

 

[mistergreen]

there are a lot of variables in a tank that affect the ph & kh, so the CO2 chart is inaccurate for the most part.

In a drop checker however, the KH is constant.. the PH changes depending on the amount of CO2 available.

 

[Left C]

Is it possible to have an planted tank pH 7 @ 6dKH without supplemental CO2 or non carbonate buffers (e.g. phosphates)? According to the chart CO2 would be ~18ppm, well above normal equilibrium values of 0-5ppm.

If I've looked at the chart right, pH 6.6 dKH 6.5 equals 49ppm CO2?
Doesn't a "drop checker" actually measure the pH (using bromothymol blue), not CO2. CO2 is then deduced from the chart according to your KH?
If your "drop checker" is green, using bromothymol blue, pH is ~6.6. Therefore, if your dKH is still 6.5 your CO2 is ~49ppm. However, if you have reduced your dKH to 4, then CO2 ~30ppm. (using the charts)
If you are interested, I am using excellent LaMotte CO2 titrator which could be used to verify your tanks parameters.
:fish1:

You most likely have other buffers present than carbonate/bicarbonate buffers in your aquarium since it is planted... Namely some phosphates which are much stronger buffers as you know.

"NOTE: If you aren't adding CO2 to your water, and the CO2 level based on the pH and KH indicates more than 5ppm, then it is very likely that some other buffer (such as phosphate) is present in your water. In an inhabited aquarium, the amount of CO2 produced by the fish will not have an effect on CO2 levels in the water. Any excess CO2 created by fish will dissipate into the air, leaving a fairly constant CO2 level of about 3-4ppm. If you test your pH and KH, and without adding any CO2, the chart says you've got 20ppm CO2, don't believe it. "

The above quote is from: http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

Most people don't rely on that chart anymore because of several variables including phosphate buffers, other acids and bases involved and inaccuracy of hobby grade test kits.

 

[qwiksilvertrav]

Sorry I misposted my numbers, I actually had a PH of 6.4 and a KH of 6.5, not a ph of 6.6..my bad. I put in my drop checker the next day and after some adjustment and increasing the Co2 it was at 30 - 40 ppm and the plants began to pearl like crazy. It most definitely was NOT at 70ppm like the chart was telling me.

 

[plantbrain]

Sorry I misposted my numbers, I actually had a PH of 6.4 and a KH of 6.5, not a ph of 6.6..my bad. I put in my drop checker the next day and after some adjustment and increasing the Co2 it was at 30 - 40 ppm and the plants began to pearl like crazy. It most definitely was NOT at 70ppm like the chart was telling me.

And since many rely solely on the chart as their metric for CO2, how might this over estimation, this belief that their test method tells them that there is much less CO2 in there than is really the case....might affect plant health, growth and algae?

The chart might work for some folks, not for others. This is a known fact and observation.

So there has to be another issue occurring besides those 2 parameters, pH/KH.

The drop checker gets around that, but............how accurate is the color changing in the DC? Can you tell between say 18ppm and 24ppm of CO2 with a DC? After adding CO2, how long does it take for the checker to change color?

How often should they(DC) be changed? What about placement of the DC?
It's a rough guide and slow to change device.

You give up one good trade off, and gain another, without really knowing if the CO2 is accurate or not.

Algae, plants, eyeballs , Riccia stones, fish, shrimp etc...........all these are perhaps better test kits for CO2. Or a mixture of all 3 methods, livestock/bioindicators, CO2 charts, and DC.

Do not rely too heavily on any one thing other than livestock.
"They" do not lie.

But folks need experience and to be careful, CO2 kills 99.99% of the fish with dosing errors, so it demands respect!

Regards,
Tom Barr

 

[!shadow!]

+1 on the above post. People usually have to find out the hard way in which l did when l was younger when my fish were gasping at the waters surface until l had to quickly add in some air stones and correct that problem. luckily none of the fish died. Anyways l couldn't agree more on that>> "Do not rely too heavily on any one thing other than livestock.
"They" do not lie." Basically don't be ignorant and follow just 1 sort of rule be open minded and experiment. Experience is often the best teacher!

 

[StaleyDaBear]

What really are we talking about? We get around dosing checks with the EI method. Then, if we experiment using fish gasping, algae and pearling as a point of reference in upping or lowering our co2, is this just not another form of EI dosing? The chart and drop checker get no closer than we ourselves can predict with a close eye on our fish and tanks, and small changes in bps. Probably a better estimate considering we dont have restrictive limitations (numbers) and nor do our planted tanks.

 

[Hoppy]

What really are we talking about? We get around dosing checks with the EI method. Then, if we experiment using fish gasping, algae and pearling as a point of reference in upping or lowering our co2, is this just not another form of EI dosing? The chart and drop checker get no closer than we ourselves can predict with a close eye on our fish and tanks, and small changes in bps. Probably a better estimate considering we dont have restrictive limitations (numbers) and nor do our planted tanks.

In pre-drop checker days, when I was having loads of algae problems, I was frustrated because when I increased the bubble rate of my CO2 my fish would definitely show they were very uncomfortable with it, so I would stop increasing it. The chart showed that I consistently had around 60-100 ppm of CO2 in the water. I knew I would kill off the fish at that rate.

After I figured out how to make a drop checker work for me I found that the discomfort my fish were showing when I increased the bubble rate was mostly my imagination. I was able to greatly increase the bubble rate to get the green color, and not lose any fish. My algae problems eased off considerably.

I think many of us, new to pressurized CO2, are nervous about gassing the fish, so are gun shy about increasing the bubble rate enough to even get close to an optimum amount of CO2 in the water. A drop checker gives you the courage to go ahead and raise the bubble rate. Once you get over that hurdle, you eventually get to see what excessive CO2 does to the fishes behavior, then you can recognize it without using the drop checker again. I see it as a learning tool, more than as a precision testing device, which it certainly isn't.

 

[Loligo]

I finally understand this, yay! For weeks now I've been reading about CO2, and it's now just finally dawned on me how to relate this chart to a drop checker. I was so focused on just understanding the process that I didn't even realize you're just checking the pH of the indicator solution. So NOW I know you take that pH reading and apply it to the chart.

Whew! I wish the first post of this thread said, "For use with a standard dKH solution. Compare the color of your drop checker to your pH test kit card, and use that reading (along with your standard dKH) to find your ppm of CO2." ...now that's here in case someone as slow as me reads this.

 

[GhostRider]

I have a 10 gallon with diy co2, and a nano diffuser. I just tested and my ph is 7.2 and my Kh is at 8 degrees, so i have a co2 level of 15ppm. am i correct?

 

[Abrium]

Drop checker newbie here. I just got my drop checker in the mail and whipped up a batch of 4 dhk standard, added my pH reagent, and threw the drop checker in the tank.

Here is where my understanding of the chemistry behind what is going on gets fuzzy and I'd like someone to explain this to me if they can. Allow me to present the facts

I have a heavily planted 125 gallon with a 10 lb pressurized system that is pumping out about 3 to 4 bps. My drop checker is yellow reflecting a pH of approximately 6.4, by the chart provided with it, and co2 levels close to 70 ppm. However, when I actually test my water parameters my pH is sitting at 7.2 to 7.4. I do have hard water here so I'm not worried about the pH crash and I have crushed up cuttle bone in my canister to ensure that my pH stays at nuetral or above for my snails but what I don't understand is the inconsistency between the drop checker and the actual pH level.

I know that during the gas exchange inside the drop checker co2 is absorbed by the pH solution lowering the pH and changing the color but with a calcium carbonate buffer skewing my readings how do I know when its accurate? I mean how valid is this yellow color that I'm seeing?

Anyone help me out on this?

 

[OverStocked]

The point of a drop checker is that you are eliminating the guesswork of messing with your ACTUAL ph/kh. You are using the controlled KH of the Drop checker. The co2 lowers the PH in the drop checker and you get a direct reading. In your tank, testing the params is basically worthless. In the drop checker you get a controlled result.

Yellow is likely 30-40 ppm. Not 70. Maybe even under 30.

Ranges of yellow are hard to read. If you ahve livestock and they are not gasping, leave it alone. The real importance of dc's is that they help you know when it is way low. They react so slowly that your fish will tell you if you have a problem long before the dc will.

 

[Abrium]

Alright, thanks a lot. That does help. So basically don't let it go into any shades of blue which shows a decrease in co2.

 

[blawrence]

I think something that has been pointed out but not absorbed.. the chart and equation are for 'perfect' water. If you are one of those people with acidic water (ph well below 7) and you are not injecting CO2.. then you don't have 'well over' 100 ppm co2. you have some other acid in your water.
go to your water source and do a ph test on it.. if it's coming out acidic, then this chart /equation may just be very useless for you.

 

[plantbrain]

I target 45-60ppm for CO2, but this is a referenced system, then I test based on the reference.

So 30ppm does not seem like the best target either.

I do not mention this typically...........because many already gas their fish due to poor control/use/testing as it is.........with CO2 gas.

But slow progressive adjust works much better, many seek absolution..........which there really is not that much ..........plants will grow over a wide range of conditions...........but the conditions which work best for your goals might be different.

So treat each case as individual, this includes folks who have more than 1 aquarium with CO2!

 

[jmullenix]

CO2 from different tank

Hello helpful reader, Is it beneficial to add water from a tank that has CO2 injected to another that does not? I am hoping to be able to plant my much larger tank and give it CO2 almost as a treat 1 time a week or so when I do water changes. My planted tank is 25g tall, and the big one is 125g and has had a turtle (diamondback terrapin), and several fish. I am considering breaking the 125 down and redoing the substrate for plants, but would like to not buy another regulator, needle valve, ect...

Also wondering how long I should wait to get fish and shrimp after first planting a tank. The water has been in for a little over 2 weeks with top soil under sand under gravel. The plants were just added yesterday. Ammonia, Nitrates and Nitrites all seem to be 0ppm. pH is around 7.5. and KH test took 10 drops, so 10 deg. I think this is all ok, but how long should I give the plants to secure roots?

Thanks,
Jason

 

[Hoppy]

Hello helpful reader, Is it beneficial to add water from a tank that has CO2 injected to another that does not? I am hoping to be able to plant my much larger tank and give it CO2 almost as a treat 1 time a week or so when I do water changes.

It isn't beneficial. You need at least somewhat constant CO2 concentration in the water, and this would be far from that. The repeated surges in CO2 concentration, followed by near zero CO2 would, at best, be of no benefit, and at worst it would encourage algae to start growing.