Plantbrain
05/02/2008, 12:56 PM
Drop checkers are devices used to measure pH in FW aquariums generally. They can be used for marine systems as well.
They work by a small air gap in between the tank's water and the solution inside the bulb.
Gas can pass through via the partial pressure in the water, so CO2 can move through, but the water and any non carbonate alkalinity cannot.
So you can have a reference solution KH or alkalinity inside the bulb.
This makes the accuracy of CO2 measurement much higher. But the color resolution is not that great at higher CO2 levels. But a lower levels and with some other pH indicator solutions, we might be better able to use and target a good CO2 range.
FW plants max out their photosynthetic capacity at 30-40ppm of CO2. Marine plants perhaps less, who knows.......
Another good thing about drop checkers,: they last 2 weeks or so before you need to replace the solution inside which takes a few minutes at most. So you can look at the CO2 at a glance anytime you walk by the tank.
Pretty handy.
There are some trade offs however.
You can also use a drop checker with a color reference.
Note, these use bromo blue which is color optimized for a pH of about 6.6 or so. thuis is fine if you want 30ppm of CO2 as a target.
More than this is generally pretty tough on FW fish, it might be as bad for marine fish or worse.
I'd say this is species dependent and the larger the fish/critter, the more impact higher levels will have.
Generally, in reefs, and marine systems, there are higher or more stable O2 levels due to much high flow rates.
Remember, respiration of the fish is a two part transfer, not just CO2. It involves O2(in) as well as CO2(out).
So both should be considered when address impacts to fish/shrimp etc.
This pH is not an issue because the drop checker uses an air gap which only CO2 will move through, not your tank's water, and the partial pressure of CO2 in the water will equilibrate with the solution inside the drop checker.
Thus the KH reference solution inside the drop checker is poure carbonate hardness of a known amount(Generally 71.44ppm-far more accurate than the 4ppm error range that the Lamotte test gives).
The trade off: color comparison, knowing what CO2 level you want for seagrasses, slow response time(2 hours is pretty good).
I use a LCO2 meter, it uses a similar thing that Tuft's developed for CO2.
You can also jerry rig a pH probe using a gas permeable membrane and add a reference KH solution inside the pH probe membrane "balloon" that keeps the tank water from mixing with the probe reference solution.
These are similar to the LCO2/LDO meters.
They have response times of 10 minutes or so and last a very long time. They also can better measure the pH so you can get to about 1ppm of CO2 accuracy if you are careful.
Due to organic acids and other potential non carbonate influences on pH, I think it's a risky issue to assume you have precise CO2 levels in marine systems, unless you pump in/out a lot of RO replacement marine water very often, I would not assume that the alk in your tank is all carbonate and a known amount so that you can standardize it with pH.
+/- 0.2pH units or a few ppm in alk and the CO2 ppm reading is severely changed.
The drop checker is a nice little item that's simple and cheaper, but does not tell me the more detailed questions I want to know.
So I use the lab stuff which is about 2500$. again, a rather pricy trade off for the accuracy and response times. You can DIY and use gas membranes around a pH probe + reference alk solutions in the "balloons".
Note, CO2 can go from 30ppm to 3 ppm in less than 1 hour, so it can have profound changes and effects very fast, so good response times and measurement is critical!
Many FW plant folks do not give CO2 enough consideration and respect, then end up incorrectly blaming nutrients for their woes.
Here's a nice drop checker with ref solution:
http://www.calaqualabs.com/doublecheck.html
You could change the indicator to target a lower CO2 level, say 5ppm or 10ppm if you wished.
Still, it's just a rough gauge.
At most of the marine CO2 levels, it will read blue as it is.
You need to use a different indicator dye that is more sensitive at high pH's and less CO2.
So take a look at this list:
http://en.wikipedia.org/wiki/PH_indicator
Phenol red
Low pH color: yellow
pH range:6.8–8.4
hi pH color: purple
Neutral red
low pH color red
pH range: 6.8–8.0
hi pH color yellow
Naphtholphthalein
low pH color :colorless to reddish
ph range:7.3–8.7
High pH color: greenish to blu
Drop checkers are easy and last about 2 weeks before you need to replace the solution in them.
Note: for the other color pH indicators, you can use a simple drop checker, not the dual more pricy one shown above:
http://cgi.ebay.com/CO2-Drop-Checke...5QQcmdZViewItem
You will need to switch out the bromo blue(unless you want 30ppm of CO2 etc). and use a lower range pH indicator for lower CO2 ppm's.
You can make your own reference KH solutions using a known standard of sodium carbonate or buy the ref solutions from Hach and dilute with DI water to make your known ref ppm standards.
I prefer more accuracy, but the method does work (but still with observations and appearances of the plants!).
I may use some seagrasses in the reef tank.
So I can explore the CO2 effect on the corals.
You will want to decide on how much CO2 you will want to add to the system, this is an arbitrary amount at this point.
As folks use it more, perhaps a better consensus will emerge.
I use 3ppm and then 30ppm at present.
I think 3, 5, 10, 15, and 25 ought to tell the story pretty well and how if effects other non target critters/macroalgae.
It's going to happen(more CO2 + corals), so I might be able to get funding(or perhaps one of you might! Hint hint!) to study it.
Haha.........have someone else pay you to test and see.
Regards,
Tom Barr
They work by a small air gap in between the tank's water and the solution inside the bulb.
Gas can pass through via the partial pressure in the water, so CO2 can move through, but the water and any non carbonate alkalinity cannot.
So you can have a reference solution KH or alkalinity inside the bulb.
This makes the accuracy of CO2 measurement much higher. But the color resolution is not that great at higher CO2 levels. But a lower levels and with some other pH indicator solutions, we might be better able to use and target a good CO2 range.
FW plants max out their photosynthetic capacity at 30-40ppm of CO2. Marine plants perhaps less, who knows.......
Another good thing about drop checkers,: they last 2 weeks or so before you need to replace the solution inside which takes a few minutes at most. So you can look at the CO2 at a glance anytime you walk by the tank.
Pretty handy.
There are some trade offs however.
You can also use a drop checker with a color reference.
Note, these use bromo blue which is color optimized for a pH of about 6.6 or so. thuis is fine if you want 30ppm of CO2 as a target.
More than this is generally pretty tough on FW fish, it might be as bad for marine fish or worse.
I'd say this is species dependent and the larger the fish/critter, the more impact higher levels will have.
Generally, in reefs, and marine systems, there are higher or more stable O2 levels due to much high flow rates.
Remember, respiration of the fish is a two part transfer, not just CO2. It involves O2(in) as well as CO2(out).
So both should be considered when address impacts to fish/shrimp etc.
This pH is not an issue because the drop checker uses an air gap which only CO2 will move through, not your tank's water, and the partial pressure of CO2 in the water will equilibrate with the solution inside the drop checker.
Thus the KH reference solution inside the drop checker is poure carbonate hardness of a known amount(Generally 71.44ppm-far more accurate than the 4ppm error range that the Lamotte test gives).
The trade off: color comparison, knowing what CO2 level you want for seagrasses, slow response time(2 hours is pretty good).
I use a LCO2 meter, it uses a similar thing that Tuft's developed for CO2.
You can also jerry rig a pH probe using a gas permeable membrane and add a reference KH solution inside the pH probe membrane "balloon" that keeps the tank water from mixing with the probe reference solution.
These are similar to the LCO2/LDO meters.
They have response times of 10 minutes or so and last a very long time. They also can better measure the pH so you can get to about 1ppm of CO2 accuracy if you are careful.
Due to organic acids and other potential non carbonate influences on pH, I think it's a risky issue to assume you have precise CO2 levels in marine systems, unless you pump in/out a lot of RO replacement marine water very often, I would not assume that the alk in your tank is all carbonate and a known amount so that you can standardize it with pH.
+/- 0.2pH units or a few ppm in alk and the CO2 ppm reading is severely changed.
The drop checker is a nice little item that's simple and cheaper, but does not tell me the more detailed questions I want to know.
So I use the lab stuff which is about 2500$. again, a rather pricy trade off for the accuracy and response times. You can DIY and use gas membranes around a pH probe + reference alk solutions in the "balloons".
Note, CO2 can go from 30ppm to 3 ppm in less than 1 hour, so it can have profound changes and effects very fast, so good response times and measurement is critical!
Many FW plant folks do not give CO2 enough consideration and respect, then end up incorrectly blaming nutrients for their woes.
Here's a nice drop checker with ref solution:
http://www.calaqualabs.com/doublecheck.html
You could change the indicator to target a lower CO2 level, say 5ppm or 10ppm if you wished.
Still, it's just a rough gauge.
At most of the marine CO2 levels, it will read blue as it is.
You need to use a different indicator dye that is more sensitive at high pH's and less CO2.
So take a look at this list:
http://en.wikipedia.org/wiki/PH_indicator
Phenol red
Low pH color: yellow
pH range:6.8–8.4
hi pH color: purple
Neutral red
low pH color red
pH range: 6.8–8.0
hi pH color yellow
Naphtholphthalein
low pH color :colorless to reddish
ph range:7.3–8.7
High pH color: greenish to blu
Drop checkers are easy and last about 2 weeks before you need to replace the solution in them.
Note: for the other color pH indicators, you can use a simple drop checker, not the dual more pricy one shown above:
http://cgi.ebay.com/CO2-Drop-Checke...5QQcmdZViewItem
You will need to switch out the bromo blue(unless you want 30ppm of CO2 etc). and use a lower range pH indicator for lower CO2 ppm's.
You can make your own reference KH solutions using a known standard of sodium carbonate or buy the ref solutions from Hach and dilute with DI water to make your known ref ppm standards.
I prefer more accuracy, but the method does work (but still with observations and appearances of the plants!).
I may use some seagrasses in the reef tank.
So I can explore the CO2 effect on the corals.
You will want to decide on how much CO2 you will want to add to the system, this is an arbitrary amount at this point.
As folks use it more, perhaps a better consensus will emerge.
I use 3ppm and then 30ppm at present.
I think 3, 5, 10, 15, and 25 ought to tell the story pretty well and how if effects other non target critters/macroalgae.
It's going to happen(more CO2 + corals), so I might be able to get funding(or perhaps one of you might! Hint hint!) to study it.
Haha.........have someone else pay you to test and see.
Regards,
Tom Barr