# What color is your drop checker (part 2)



## ray-the-pilot (May 14, 2008)

OK I’ve been doing this aquatic plant aquarium for almost 2 years now and it has become pretty easy to grow plants. 

There is one thing; however, that completely baffles me. How can anyone keep fish in an aquarium with 30 ppm of CO2?

I have tested this up, down and sideways at least 3 different ways and (in my tank at least) if the CO2 level gets to 30 ppm my fish show signs of stress. This level of CO2 corresponds to a dark-green color in my Drop Checker. 

How can anyone maintain fish with a green or yellow Drop Checker?

I recently reconfirmed this conclusion when my regulator went down. I had to return it and my tank was without CO2 for 12 days. By the time the regulator returned, there was a fairly well established crop of blue green algae. 

I guessed that increasing my CO2 slightly might help rid the problem; so I increased my by KH level by adding some extra city water to my tank. The drop checker went from blue-green to a slightly lighter dark green. By the next day I had fish showing signs of distress. A catfish was swimming upside down and an angel was at the surface gulping air. 

Stupid me!

Just so you know I am really anal about making up my DC solution. I weigh out exactly 120 mg of NaHCO3 on a balance that measures to +/- 0.1 mg. I dilute to 1L in a volumetric flask. It is 4 deg. KH.

Does anyone have an opinion on how it is possible to keep fish in a tank where the DC is yellow? Or why I cannot maintain fish at this level of CO2?


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## freshyleif (Jan 9, 2008)

Is your water very hard I read that to much Ca can cause problems with CO2 levels in the water. I also found that for me it was because of dead spots in the tank circulation.( its to big and box shaped) When I added more circulation I could add more CO2. Another question, how much surface agitation do you have? It could be that the oxygen levels are to low and that is what the fish are reacting to. Some guesses to give you ideas hopefully.


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## ray-the-pilot (May 14, 2008)

freshyleif said:


> Is your water very hard I read that to much Ca can cause problems with CO2 levels in the water. I also found that for me it was because of dead spots in the tank circulation.( its to big and box shaped) When I added more circulation I could add more CO2. Another question, how much surface agitation do you have? It could be that the oxygen levels are to low and that is what the fish are reacting to. Some guesses to give you ideas hopefully.


Hey thanks for the input!

My water is soft. I use RO with added city water. I aim for about 75 ppm total hardness. This is usually 5-1 to 2-1 Ca/Mg.

Variability of CO2 in my tank is less than +/- 2 ppm. I know because I've checked it at several location in my tank many times.

Aeration may be a problem this last time; since, I turned off my bubbler but I had this issue even with the bubbler on. Also since my plants are pearling full out, my expectation is the the water is saturated with O2 otherwise the plants wouldn't pearl!

As I said before, I can grow any plant I want and my fish are fine at the low CO2 level. It just seems that there is something out of calibration.


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## Left C (Jun 14, 2005)

I reversed your post to write something about the last part first that may help to bring things into perspective (I hope).



ray-the-pilot said:


> Just so you know I am really anal about making up my DC solution. I weigh out exactly 120 mg of NaHCO3 on a balance that measures to +/- 0.1 mg. I dilute to 1L in a volumetric flask. It is 4 deg. KH.


For the calculations below, I used 0.264200793 gallons for one liter (1 gal/3.785 liters per gal) and 71.44 ppm for 4 dKH (17.86 ppm per dKH x 4 dKH) with the CNYKOI Alkalinity (KH) calculator for my calculations.

It takes 100 mg of baking soda to make a one liter of 4 dKH solution. Using 120 mg makes a 4.8 dKH (85.73 ppm) solution.

I don't know your exact pH, so let's look at two possible pH levels to calculate the CO2 level by using Chuck's calculator. At a 4.8 dKH and a pH of 6.6, this is 36.171 ppm of CO2. At the same KH, a pH of 6.4 has 57.327 ppm of CO2.

So, if this calculator is correct, this may be one problem. This may be what the fish are telling you.



ray-the-pilot said:


> ... I guessed that increasing my CO2 slightly might help rid the problem; so I increased my by KH level by adding some extra city water to my tank. The drop checker went from blue-green to a slightly lighter dark green. By the next day I had fish showing signs of distress. A catfish was swimming upside down and an angel was at the surface gulping air. ...


Increasing the KH level doesn't change the CO2 level in and by itself. It does increase the pH though, but the CO2 level remains the same. The CO2 level can be increased only by adding more CO2.

If a pH controller is used, adding KH will raise the pH causing the controller to add CO2 until its set point is reached. Then it turns off. So, the CO2 level is increased this way.

From Chuck's "Measuring CO2 levels in a Planted Tank", he writes:

*Myth: CO2 level can be adjusted simply by adding chemicals to alter the KH or pH.*
This is a common misconception when using the CO2 / KH / pH table. It appears that by altering any parameter, the other values should move. But this is not true. Treat the pH value you see as a result. If you alter the KH, then the pH will move. If you alter the CO2 level, then the pH will move. The pH will always react to changes in either of the other two parameters.

*Example:* My water comes out of the tap with a KH of 3 degrees, and a pH of 7.6, which according to the chart indicates a CO2 level of 2.3ppm. Looking at the chart, I might (incorrectly) assume that If I simply raised my KH to 10 degrees, I would end up with the same pH, but the CO2 level would now be 12ppm! How easy! I can add CO2 just by adding some baking soda to raise my KH.

BUT! it doesn't work that way. Instead, as I raise the KH, the pH will rise along with it, and the indicated CO2 level staying at it's 2.3ppm. In my case, if I raised the KH to 10 degrees, ...

You can not alter the KH levels other than by adding or removing carbonate. You can not alter the CO2 levels other than by adding or removing CO2.



ray-the-pilot said:


> ... There is one thing; however, that completely baffles me. How can anyone keep fish in an aquarium with 30 ppm of CO2?
> 
> I have tested this up down and sideways at least 3 different ways and (in my tank at least) if the CO2 level gets to 30 ppm my fish show signs of stress. This level of CO2 corresponds to a dark-green color in my Drop Checker.
> 
> How can anyone maintain fish with a green or yellow Drop Checker? ...


If the above is correct, could you possibly have too low of a O2 level?

You didn't mention pearling which indicates ~ 100% O2 saturation. Do you have pearling?

EDIT: I just saw your next post saying that your plants are pearling.


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## freshyleif (Jan 9, 2008)

I know the feeling. I generally think my Co2 is not at 30ppm myself but the plants are pearling so who knows. I have only used a air bubbles when my fish look stressed so I am out of guesses.


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## wet (Nov 24, 2008)

Left C said:


> Originally Posted by *ray-the-pilot*
> _Just so you know I am really anal about making up my DC solution. I weigh out exactly 120 mg of NaHCO3 on a balance that measures to +/- 0.1 mg. I dilute to 1L in a volumetric flask. It is 4 deg. KH._
> For the calculations below, I used 0.264200793 gallons for one liter (1 gal/3.785 liters per gal) and 71.44 ppm for 4 dKH (17.86 ppm per dKH x 4 dKH) with the CNYKOI Alkalinity (KH) calculator for my calculations.
> 
> ...


I think this may be incorrect. 1 degree of KH is 17.86 ppm CaCO3 (more useful to reefers as they usually add both Ca and KH buffering), but baking soda (NaHCO3) doesn't have Ca. So, when calculating we translate that 17.86 ppm CaCO3 to its CO3 (carbonate) equivalent, which is 10.7 ppm CO3 for each dKH. If so, ray-the-pilot's calculations are correct.

But I may be wrong. I think it was Hoppy who explained this best but cannot find it in a quick search. Maybe Salt?


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## Left C (Jun 14, 2005)

wet said:


> I think this may be incorrect. 1 degree of KH is 17.86 ppm CaCO3 (more useful to reefers as they usually add both Ca and KH buffering), but baking soda (NaHCO3) doesn't have Ca. So, when calculating we translate that 17.86 ppm CaCO3 to its CO3 (carbonate) equivalent, which is 10.7 ppm CO3 for each dKH. If so, ray-the-pilot's calculations are correct.
> 
> But I may be wrong. I think it was Hoppy who explained this best but cannot find it in a quick search. Maybe Salt?


I used the Koi KH calculator hyperlinked above to derive those amounts. Is this calculator wrong, I wonder?

Its last field is "Amount of Baking Soda" needed to increase x gallons to y ppm KH change. It uses 17.86 ppm for 1 dKH.
http://www.cnykoi.com/calculators/calckh.asp

From: http://fins.actwin.com/aquatic-plants/month.9712/msg00259.html
I found something like you mentioned: 1dkh = 17.8575 mg/liter CaCO3. 7.143 mg/liter of this is Ca,
the rest; (17.8575 - 7.143) = 10.7145mg/liter CO3

I've got to keep on digging. I haven't what I need yet.

All of Ray's comments led me to believe that it is simply something fundamentally out of whack a bit. Hence the KH calculator.


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## Philosophos (Mar 1, 2009)

Here's a handy old standby:
http://www.thekrib.com/Plants/CO2/hardness-larryfrank.html



> If you want to raise the alkalinity by 1dKH using NaHCO3:
> 
> mw Na = 23
> mw HCO3= 61
> ...


They round a bit, but it's easy enough to change those numbers out.


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## Left C (Jun 14, 2005)

I saw that last night and cut my computer off. I even posted it and later deleted it. I was confused. ... 17.86, 10.7145, 30 ...  :lol:

My posted link above in Post #7 ( http://fins.actwin.com/aquatic-plants/month.9712/msg00259.html ) which is by Larry Frank too and written on the same day (Date: Tue, 16 Dec 1997). It has the same example at the bottom.

_How to use these conversion factors:

If you have alkalinity in ppm or hardness in ppm divide by 17.86 to get degrees.

If you want to raise the alkalinity by 1dkh using CaCO3: use 17.86 mg CaCO3
If you want to raise the alkalinity by 1dkh using NaHCO3:
mw Na = 23
mw HCO3 = 61
mwNaHCO3 = 84
1dkh = 21.8 ppm HCO3
21.8 *84/61 = 30 mg/liter of NaHCO3

using molarity: 0.358 mMoles * 84 (mwNaHCO3) = 30 mg/liter of NaHCO3_

So, using 120 mg NaHCO3 in 1 liter to make a 4 dKH solution is correct then.

The Koi KH calculator isn't correct, right? It comes up with 100 mg of NaHCO3 to make a 4 dKH solution using 1 liter of water because it uses 17.86 ppm in 1 dKH.

I'm sorry, Ray. I thought that I stumbled across your problem. Your problem seems like it would be something obvious.


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## Philosophos (Mar 1, 2009)

Easy is always nice. To be honest, I'm stumped as well. Nothing looks obvious, but I might as well ask the obvious.

Perhaps oxygenation is actually an issue. If you put an airstone in a tank, it should remove the CO2 very quickly. My drop checker goes blue fast with an air stone in and CO2 on.

How does your surface disturbance look? Any film developing? I've found that low surface disturbance with any film makes life a lot harder; I've even gone to the point of using a powerhead near the surface to break things up at times.


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## ray-the-pilot (May 14, 2008)

Philosophos said:


> Easy is always nice. To be honest, I'm stumped as well. Nothing looks obvious, but I might as well ask the obvious.
> 
> Perhaps oxygenation is actually an issue. If you put an airstone in a tank, it should remove the CO2 very quickly. My drop checker goes blue fast with an air stone in and CO2 on.
> 
> How does your surface disturbance look? Any film developing? I've found that low surface disturbance with any film makes life a lot harder; I've even gone to the point of using a powerhead near the surface to break things up at times.


Thanks guys!

Here are a few more details.

I am running with a CO2 controller. I set it to pH 6.7 and to increase CO2 levels, I add any alkali like my city water. To decrease CO2 I add any acid. My kH is about 4.0. This corresponds to a CO2 level of 24 ppm which, I have checked chemically 2 different ways. If my kH goes above 5.0, I start having problems.

When my fish showed signs of distress, I turned off the controlled and set my bubbler full on. The pH went up to 7.5 and the drop checked turned blue in about 2 hours. If I leave the controller on it just pumps CO2 faster keeping the pH level constant and wasting CO2.

Set at 24 ppm my plants always pearl. Actually, like I said, growing plants is easy and I wish I could find really slow growing plants so I don't have to overhaul my tank as often.

BTW the surface of my tank is partially covered by Cabomba fucata in bloom! But I would not say that it was cutting off air circulation.

I was thinking that maybe if you have a higher kH the CO2 is less toxic? Is anyone running at a low kH and a yellow or green DC?


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## Philosophos (Mar 1, 2009)

So you're changing your pH for the sake of the controller?

If not, changing your pH won't change your CO2. The CO3 from CaCO3 is bound to calcium; functionally useless to anything but some hard water plants with the ability to break that bond. It's definitely not going to gas off into your drop checker to change any reading.

On the other hand, swinging your pH up and down with acids and buffers is going to cause some real osmotic stress to your fish by altering carbonate hardness.

I'm not sure why higher KH would make CO2 less toxic. The entire CO2 thing is an issue of acidosis as a matter of hemoglobin and oxygen uptake, not osmotic pressure. Having stress from altering both is probably worse than either individually, but it isn't compounded by any direct interaction.

I'm running ~6.5pH in my tank with a yellow-green DC and no problems with apistos; two pairs in spawn right now.


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## Left C (Jun 14, 2005)

Hi Ray

You really shouldn't be playing with your KH. As you've seen, when you increase the KH and keep the same pH setting on the controller will increase the CO2 level. 

If your KH level is 1 degree or higher, you really don't have to adjust it. You are throwing another variable to chase around.

As we know CO2 and O2 can be 100% saturated independently and separately from each other. You mentioned that you aren't getting much O2 since your surface is covered with plants. This is what I would do:
- Add a timer to control your solenoid. Have it on when the lights are on for CO2 addition and off when the lights are off. You don't need the CO2 when the lights are off anyway.
- When the lights and CO2 are off, add aeration to increase the O2 level. Then cut it off when the lights are on. If your fish tell you that they need more O2, run the aeration longer.
- You can add a staggered timing system to control this more optimally. 

Adding O2 and leaving your KH alone should fix your problem, I do believe.

Left C


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## Left C (Jun 14, 2005)

I got Ninjaed by Philosophos.


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## Philosophos (Mar 1, 2009)

I know O2 in and of its self through surface disturbance won't cause big issues. Adding O2 through an air stone seems to gas off CO2 fast though. It's hard to apply partial pressure in a normal way to a supersaturated column of bubbles constantly rising to the surface. What ever actually causes the drop, my drop checker confirms that it's happening.


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## Left C (Jun 14, 2005)

I posted this yesterday. Chuck is saying what Philosophos is telling you.

Increasing the KH level doesn't change the CO2 level in and by itself. It does increase the pH though, but the CO2 level remains the same. The CO2 level can be increased only by adding more CO2.

If a pH controller is used, adding KH will raise the pH causing the controller to add CO2 until its set point is reached. Then it turns off. So, the CO2 level is increased this way.

From Chuck's "Measuring CO2 levels in a Planted Tank", he writes:

"*Myth: CO2 level can be adjusted simply by adding chemicals to alter the KH or pH.*
This is a common misconception when using the CO2 / KH / pH table. It appears that by altering any parameter, the other values should move. But this is not true. Treat the pH value you see as a result. If you alter the KH, then the pH will move. If you alter the CO2 level, then the pH will move. The pH will always react to changes in either of the other two parameters.

*Example:* My water comes out of the tap with a KH of 3 degrees, and a pH of 7.6, which according to the chart indicates a CO2 level of 2.3ppm. Looking at the chart, I might (incorrectly) assume that If I simply raised my KH to 10 degrees, I would end up with the same pH, but the CO2 level would now be 12ppm! How easy! I can add CO2 just by adding some baking soda to raise my KH.

BUT! It doesn't work that way. Instead, as I raise the KH, the pH will rise along with it, and the indicated CO2 level staying at its 2.3ppm. In my case, if I raised the KH to 10 degrees, ... (Chuck doesn't finish this sentence.)

You can not alter the KH levels other than by adding or removing carbonate. You can not alter the CO2 levels other than by adding or removing CO2."


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## ray-the-pilot (May 14, 2008)

Let me try to explain this.

In my tank, the pH is always 6.7, this is a constant controlled by the CO2 controller and the KH is normally around 4. 

If you go to Chuck’s page and plug in: 
pH = 6.7 and KH = 4.0 you get CO2 = 23.9 ppm (this is ideal for me)

then plug in:
pH = 6.7 and KH = 5.0 you get CO2 = 29.9 (this is bad for me)

My bad was that I added some extra city water that brought the KH up to 5!

Now anything that is a base will increase KH and anything that is an acid will decrease KH. If you add: NaHCO3, NaOH, city water at a pH of 8 or any other base the KH increases but the pH of my tank stays the same because of the controller. The result is that the controller adds more CO2 to maintain the correct pH. 

Here is what happens when you add NaOH to your tank:

Na OH + CO2 (from the controller) -- > Na HCO3 -- > Na+ + HCO3- Carbonate increases.

Here’s what happens when you add any base:

X OH + CO2 (from the controller)-- > X HCO3 -- > X+ + HCO3- Carbonate increases

If you want to change the CO2 level in a tank with a controller, you can do it 2 ways; decrease the pH setting or increase the KH. Obviously, you do either of these slowly. 

Anyway, I’ve reduced my KH from 5 to 4 and my DC is back to blue - green. My plants are pearling, my fish are happy but I still do not know how anyone can keep fish in a tank with a green DC.


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## bartoli (May 8, 2006)

If your CO2 regulator's bubble rate was relatively high and the pH value was relatively slow to catch up (due to a slow pH probe and/or poor water flow), for a period of time the level of water CO2 could be much higher than expected and therefore caused problem to the fish.


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## ray-the-pilot (May 14, 2008)

bartoli said:


> If your CO2 regulator's bubble rate was relatively high and the pH value was relatively slow to catch up (due to a slow pH probe and/or poor water flow), for a period of time the level of water CO2 could be much higher than expected and therefore caused problem to the fish.


That is a possibility! :idea:

I have an electronic regulator and it was out for repair. When it came back I never bothered to check the bubble rate. Normally it is at 1 bubble every 2 sec. now it is at over 1 bubble per sec.

I turned the rate back down to 1/2 BPS.

Thanks for the info.


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## Left C (Jun 14, 2005)

Couldn't you put your CO2 controller on a timer and turn it off when the lights are off? You don't need the CO2 anyway and you would give your fish a break. Even run a bubbler or increase surface agitation at night to increase O2.

There are quite a few folks running drop checkers green or even lime green without problems.

You just don't have enough O2 for the fish.


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## wet (Nov 24, 2008)

FWIW, I think it's the KH swing that's affecting the fish.

You could test by leaving KH alone and dropping the pH on your device, say, 0.1 pH gradually, to isolate CO2.

Also keep in mind that a drop checker is only as accurate as your ability to figure out its color. "Green" at 4dKH could be ~50ppm CO2.

Just more ideas.


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## wet (Nov 24, 2008)

Left C - In regards to dKH conversions, I think Larry Frank is correct and that other calculator is suspect, also FWIW.


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## ray-the-pilot (May 14, 2008)

Hey thanks for your thoughts!



wet said:


> You could test by leaving KH alone and dropping the pH on your device, say, 0.1 pH gradually, to isolate CO2..


That is what you do when you first set up your controller to find the right CO2 level. You start at a high pH and gradually lower it observing the plants and fish. 
That is when I first discovered that 30 ppm was too high.

Here are some interesting facts:

If you go to Chuck's page and plug in these values:

pH = 6.7 KH = 4 Result CO2 = 23.0
pH = 6.6 KH = 4 Result CO2 = 30.1
pH = 6.7 KH = 5 Result CO2 = 29.9

That means that one degree change in KH has the same effect as a 0.1 pH change.

For me, at least, it is easer to make small increases in KH than trying to tweak my controller less than 0.1 pH. To change the KH in my tank I need to add 3.5 gm of CaCO3 to increase the KH 1 deg.

At 4 deg. KH, a 1deg change in KH will increase the Ca level by 33%
A pH 0.1 change increases the H+ level by 26 %

So the ionic strength is increased slightly more changing the KH but not a lot more.



wet said:


> Also keep in mind that a drop checker is only as accurate as your ability to figure out its color. "Green" at 4dKH could be ~50ppm CO2.
> 
> Just more ideas.


This is true. Someone needs to put a tiny pH probe in a DC that reads out in ppm CO2 directly.

When I did my set up and adjusted the pH, I knew from my fish and plants:

blue - green = good 
green = bad


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## Left C (Jun 14, 2005)

wet said:


> Left C - In regards to dKH conversions, I think Larry Frank is correct and that other calculator is suspect, also FWIW.


That threw me a curve too. :lol:

Thanks!


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## Left C (Jun 14, 2005)

ray-the-pilot said:


> ... If you want to change the CO2 level in a tank with a controller, you can do it 2 ways; decrease the pH setting or increase the KH. ...


Let's examine these two ways to increase the CO2 level.
- decrease the pH setting increases the CO2 level - This is true. It is an one step process to add more CO2. The controller adds CO2 until it reaches its new set point.

- increase the KH increases the CO2 level - This is a two step process to add CO2. First, the pH is raised because of the increased KH. Then the controller adds CO2 until it reaches its set point.

- Your controller is set on 6.7 and a KH of 4. This is 23.9 ppm of CO2.
- You increased the KH to 5. Then the pH increases to ~ 6.8. The CO2 level remains to same.
- Then your controller turns on and starts adding CO2 until it lowers the pH to its set point of 6.7. This results in 29.9 ppm of CO2.

The above agrees with what Chuck says. Myth: CO2 level can be adjusted simply by adding chemicals to alter the KH or pH.

- This is a common misconception when using the CO2 / KH / pH table. It appears that by altering any parameter, the other values should move. But this is not true. Treat the pH value you see as a result. If you alter the KH, then the pH will move. If you alter the CO2 level, then the pH will move. The pH will always react to changes in either of the other two parameters.


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## Left C (Jun 14, 2005)

Hi Ray

Earlier you mentioned adding tap water to your RO water.

Can you lower your KH to ~ 1 to 2? Then adjust your pH level with your controller to get the CO2 level that you want.

This would lower the TDS. Maybe, your fish would like it.

Left C


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## Philosophos (Mar 1, 2009)

You know, we haven't talked about drop checker location either.

I've told people to put their drop checkers near the bottom of their tank or dead flow areas on some, "My Drop Checker is Yellow and I Have BBA" threads, which invariably results in a blue/dark green drop checker. Perhaps the drop checker is in a dead zone that's not getting decent distribution? I figure it's at least worth asking.


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