# One drop checker is good. Two is better.



## wet (Nov 24, 2008)

So I killed a bunch of fish earlier after moving my CO2 injection point to right after my Mag pump. I am pissed with myself for this. So I decided to finally do something I've been thinking of doing for a while: find out (almost) exactly how much CO2 is in my tank.

Now, the problem with regular drop checkers is it's hard to know what "green" means. Our human eyes and, well, nerds in general, have difficulty differentiating such minute color shades as available on low range B. blue-based pH charts. For example, this is a regular drop checker with 4dKH. 









If it is perfectly green, I have 30ppm CO2. If my eyes can only tell shades of green +/- 0.2 degrees pH, it only says I have between 18.9 and 47.5ppm CO2.

Pretty crappy, right?

So, here's a second drop checker at 9dKH. It is green, so it says I have between 42.9 and 107.8ppm CO2.










I use both of them together, and both are green, so now I know I have between 42.9 and 47.5 ppm CO2.

The calculator:
http://wet.biggiantnerds.com/drop_calc.pl

Suggestions and thoughts appreciated. <3


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## Scottso (Mar 6, 2010)

Awesome. I came to the exact same conclusion you did and did the exact same thing! (Great minds??) I've also concluded since 40ppm+ CO2 will almost certainly kill my shrimp and/or fish that there are other factors in my water leading to the "proper" green color. So in reality I have 30ppm or less most likely but it's pretty darn close!

Certainly once I did this and made both drop checkers green all my algae issues have magically disappeared.


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## medicTHREE (Feb 5, 2010)

Scottso said:


> Awesome. I came to the exact same conclusion you did and did the exact same thing! (Great minds??) I've also concluded since 40ppm+ CO2 will almost certainly kill my shrimp and/or fish that there are other factors in my water leading to the "proper" green color. So in reality I have 30ppm or less most likely but it's pretty darn close!
> 
> Certainly once I did this and made both drop checkers green all my algae issues have magically disappeared.


I think you misunderstand how a drop checker works. Assuming that you have a correct 4dkh solution in your drop checker, nothing outside of co2 gas is going to effect the pH in the drop checker. Sure, tanic acids and such could effect the pH in your tank, but NOT in your drop checker. That is the ENTIRE point of a drop checker. If it could be effected otherwise, it would be pointless to use instead of the simple chart it is based on.

It is entirely reasonable that fish can live at 40 ppm of CO2.


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## SJInverts (May 26, 2009)

Great idea!!!


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## Scottso (Mar 6, 2010)

medicTHREE said:


> I think you misunderstand how a drop checker works. Assuming that you have a correct 4dkh solution in your drop checker, nothing outside of co2 gas is going to effect the pH in the drop checker. Sure, tanic acids and such could effect the pH in your tank, but NOT in your drop checker. That is the ENTIRE point of a drop checker. If it could be effected otherwise, it would be pointless to use instead of the simple chart it is based on.
> 
> It is entirely reasonable that fish can live at 40 ppm of CO2.


Apologies, I had a bit of wine in me when I wrote that and I obviously left out a bunch of info. I use a PH meter to regulate my CO2 and before setting up the second drop checker I could make the 4dkh solution turn what seemed to be over 40+ ppm of CO2 but I couldn't be sure because colors are very subjective. Once I put the second drop checker in there I discovered I could lower my PH a lot more as the green I thought was way into danger zone was not. So when I was referring to "other stuff in my water" I meant that I could drop my PH much farther down than I would have expected solely based on the color of the single 4dkh drop checker and even based on the various charts that say x amount of PH is x amount of CO2.

In any case I will refrain from posting while tipsy in the future. 

That said, everything I've read prior to your statement says that over 30ppm is well within the danger zone for many fish and all shrimp. Is it really reasonable to expect fish to live at 40ppm or is that just anecdotal? I've read many a horror story where people gassed half their tank just trying to approach 30ppm.


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## wet (Nov 24, 2008)

Thanks all  Anybody tried it and have experiences to share?

Scott,

I think that stress is from fast CO2 swings, like an immediate 50% raise from 20 to 30 ppm CO2 or more. You'll find fish can adapt to most anything provided you do it slowly enough. But high CO2 does not seem to be a form of controlled stress but rather balance: if gas exchange is good (surface ripple) and O2 high (pearling plants), CO2's levels of toxicity is high. Break one of those and the CO2 may be more important.

In this tank, my CO2 changed quickly and the readings above were after turning CO2 down and increasing surface agitation to try to save the remaining fish and not seeing stress after the mistake. My target under this high light is still ~35-40ppm CO2 unless the fish, plants, or algae tell me it's time to adjust.

I hope this helps.


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## Scottso (Mar 6, 2010)

That's interesting. I'm not clear on what you mean by CO2's level of toxicity is high if gas exchange is good and O2 saturation is high. Are you saying those two factors can make CO2 more or less toxic to life in the tank?


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## wet (Nov 24, 2008)

I am, but purely from my anecdotal experience with high tech tanks. For practical purposes, I mean that 30ppm CO2 in a tank with low gas exchange and O2 can be a problem. 40ppm CO2 in a tank with high gas exchange and plenty of O2 often isn't a problem.


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## wet (Nov 24, 2008)

It's been about a month since sharing this idea and calculator: any new insight, thoughts, ideas, experiences?

Thanks!


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## Left C (Jun 14, 2005)

http://wet.biggiantnerds.com/drop_calc.pl

I think you should take new pictures without the flash. All I see is a welding spark on each one. LOL

I couldn't resist this. I'm still chuckling. :lol:

Left C


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## wet (Nov 24, 2008)

K. It's actually sunlight with no flash  I had hoped this would better show the color of the drop checkers.

I realized after looking closer at the tank after pics that the top drop checker was closer to blue, suggesting I was not quite at its lower limit. I slowly adjusted CO2 and waited for the drop checkers to adjust. So, an effective use of the tool. 

For my new pics, my tank is changing and it's a good time to reassess, too. Probably this weekend if I'm home while the light is good.


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## Revan (Dec 26, 2005)

Good Idea! 

Compliments


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## drunkenmastera (Oct 21, 2009)

would it work if i put two drop checker at opposite ends of the tank?
If both read green between 30 ppm, would that be suffice to assume I have 30 ppm?


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## wet (Nov 24, 2008)

Sorry for missing that drunkenmastera.

If you put two drop checkers on opposite sides of the tank, it would work well to get a ballpark at the areas around the drop checker. Such a method is good because it can ensure circulation is good, and two drop checkers at the same KH can have some benefits as a sanity check. But you're approaching a different kind of problem.

The calculator here operates on the idea that a green drop checker isn't necessarily at 30ppm, but could be, say, 15ppm or 40ppm or any number of values. So, if we use two drop checkers with different KH solutions, the area they overlap makes a smaller ballpark.

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Just spreading around an update to this calculator with additions from Hoppy/VaughH/hoppycalif's ideas here: http://www.plantedtank.net/forums/f...ters/129720-drop-checker-new-way-use-one.html

The address for this new version is http://dropcheck.petalphile.com

These additions are:
1) Maybe you find yellow easier to read than green, and if so, the calculator will make KH solutions for you.

Hoppy's method doesn't not take a margin of error for yellow like I do here with green, so neither does the calculator when calculating for yellow.

2) If the calculator returns a mix with less than 1dKH, there's an error from Hoppy explaining why this is a bad idea (poor buffering) and a message from myself saying we'll adjust this number per future experiments.

3) Populates a pH color chart with CO2 values for your calibrated mixes. Another of Hoppy's ideas that I think is brilliant.

It'll look like this for yellow:









And this for green:









4) Lets you pick a margin of error from +/- 2.5-30ppm CO2. Very conservative folks will calculate with high margins of error. Folks who feel they can make precise and accurate solutions should mess around with small margins of error. The calculator explicitly explains there's always a margin of error and treats the rest as a math problem.

The old version at http://co2.petalphile.com is still around but may move. I'll always keep that version around somewhere with a link.

Have fun; suggestions here or the thread above are appreciated.


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## wet (Nov 24, 2008)

Spreading around more updates to the calculator:

1) Added example of a two drop checker setup from Pat W.
2) Added credits for photos, etc.
3) Separate sections/accordion for Instructions, Calculator, and Credits.
4) "prettier" forms, if you want to call it that...

5) Centered the pH chart values.
6) Faster!
7) Bug fix for one drop checker calibrated for green incorrectly saying "yellow" in the instructions. (The calculation was not in error.)
8 ) Removed the "beta" flag, instead calling it version 0.2

Thanks!


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