Once again I've been fiddling with my co2. I added more plant mass and said plant mass has been growing well, so I upped co2 - to the point of almost gasing my fish, then backed it down to probably too low of a level. Needless to say I have all kinds of algae at this point.

So I finally broke down and bought a drop checker from a fella at the plantedtank. I thought I was good. The first use of the drop checker took about 3 hours to turn green, but the problem I'm having is it never goes back to blue. By the next day it's yellow and the next day is even yellower.

The drop checker kit comes with a bottle of blue solution. First I tried mixing a little with distilled water, but could not read the color, so I now use it straight.

It seems to me that my co2 level does not dissipate at night, but continues to increase up to water change day. The behaviour of my fish seem to indicate this as well. I have my filter outlow creating constant and massive turbulence at the top of the water, yet the drop checker stays yellow all the time, even right before lights on when its had almost 14 hours of no co2.

I am just not doing well with co2.

edacsac,
If the plants were doing well why did you change the CO2 so soon? The drop checker always takes a few hours to respond to the CO2 level in the tank. Also it takes a few hours for the CO2 to disperse and to saturate the tank water. Normally, you want to turn on the CO2 an hour or two before the lights come on that way there is a stable, high concentration when the light initiates photosynthesis. You can also turn the CO2 off 2 hours before the lights go off. Now, when you turn off the CO2 it doesn't mean that the CO2 in the water suddenly disappears, especially if the tank is tightly covered. Think about an open bottle of coca cola. How long does it take to go flat? The gas has nowhere to go so it simply dissipates slowly overnight, but may not completely evacuate by the next morning.

The second problem is that you don't seem to be using the proper water in the drop checker. Check out this site:

Measuring CO2 levels in a Planted Tank

It discusses the relationship between the pH, the kH and the dissolved CO2 concentration in a sample of water. When CO2 dissolves in water it forms carbonic acid which changes the pH of the water. This relationship is only valid when CO2 is the sole source of acid in that water.

That blue solution that come with the kit? All it does is show you the pH of the water sample. If your water sample is pH 7 or above it stays blue. As the pH of the sample starts to turn green it means the pH is approaching 6. When the sample turns yellow the pH is below 6. Ideally, we want a CO2 concentration of about 30 ppm, and when that happens we want the water sample in the drop checker to be a nice lime green, which if you check the color chart on your drop checker kit means that the pH of that water sample will be about 6.6. Now check that link I gave and look at the bottom of that page. Can you see that in order for the pH to be 6.6 at the same time when the is 30ppm CO2 in the sample the kH of that water sample needs to be exactly 4 kH?

So can you also now see on that chart that if you use distilled water in the drop checker, and lets say the kH of that water is for example, 2, the water will turn green at less than 4 ppm CO2 concentration? At only 10 ppm the drop checker with that water will already be at a pH of 6 and will be yellow. So you wouldn't know the difference between 10 ppm CO2 and 60 ppm CO2 using that water in the drop checker because it would all be yellow.

Likewise, if you used tank water, or even tap water in the drop checker, you have no idea what dissolved acids are in the water to affect the pH of your sample. There may be no acids but the kH of the water may be say, 8. Back to the chart. Can you see that at a kH of 8 the water sample will reach pH 6.6 only when you have 60 ppm of dissolved CO2?http://www.barrreport.com/images/smilies/eek.gif


If you are not using a 4 dkH water sample in your drop checker, or if you are unsure of the chemistry of the water sample you are using in the drop checker you have absolutely no idea how to interpret the colors of the checker and therefore you have no idea whatsoever of your actual CO2 concentration.

Once you have mastered the concept of the drop checker and why it works, CO2 will be much less of a mystery than it is currently, and you will be easily able to regulate to the proper levels. You'll never ever again be able to say "I am just not doing well with co2" .http://www.barrreport.com/images/smilies/biggrin.gif


By the way, 4dkH water is available at online shops. Making it is possible but is a bit of a drag. It's much easier to buy.

Cheers,

So, I'm not even sure what a drop checker is, I use the regular drops and test tubes, but if there's a better way, where do I find this stuff? Also, I bought a Milwaukee SMS 122, with the PH controller/monitor and I'm having trouble with it. It reads a much much lower ph than the tank actually has, and therefore has little use as far as regulating CO2. Everyone else I've read about raves about their accuracy, so what am I doing wrong? It seems calibrated, b/c when I put it in a glass of aquarium water, it goes up to the right ph! Please help, anyone....

I'm sure that eventually you will get your CO2 system working. Everybody does, if they put enough effort and money into it.

But if you get tired of all that, an alternative is the "low tech" approach (or "natural" or "Walstad" approaches). This features a soil substrate, lower light, and usually no nutrient dosing nor CO2. Plants grow well and they don't require the constant attention that the higher tech tanks do.

Tom Barr has written about this and there is a board that is dedicated to it: http://www.aquaticplantcentral.com/forumapc/el-natural/

(Why do I feel like a subversive when I post about this approach?)

Good luck!

Bill

Perhaps you/we are subversive

Using low light, high biomass, good current and CO2 should be fairly easy to do.


Regards,
Tom Barr

I'm totally getting a drop checker, but as far as keeping the system automated, should I put the probe in a spot without current, or away from plants, higher, lower, etc? I'm a little bit upset that I spent all this money on this fancy gadget and it isn't working...

Probes of every sort should be placed in higher current regions.

You may use probes as a relative measure of CO2.

Say based on the pH drop checker, you now know a target CO2, you may correlate that information with the pH probe.

KH can change however, and there is a 2 hour lag time with the pH drop checker.
There is also color resolution with respect to your/our eyes(about 0.2pH units if you are good).

One could use a spectrophotometer if they could syringe the solution out of the sealed pH drop checker and place it in the spect to get a pretty accurate reading also.

They are far better than eyeballs

FYI, everyone fails with CO2 and makes a lot more assumptions with this one parameter than any other in the hobby.

This leads me and others to suggest less light, non CO2 methods etc.

But failures are how we learn, trick is not to do the same ones over and over and get too full of one's self to admit you might be overlooking something and blaming the wrong thing.

I've made plenty of mistakes, so I no longer trust myself
I have to double check and verify. We all should.





Regards,
Tom Barr

Ok, so you guys are totally awesome But I have another question-- I bought a Red Sea drop checker, and the instructions said to put aquarium water in it. I have no idea what the actual reagent inside of it is, so I'm not sure if it's measuring CO2 in the air, or if it's measuring CO2 as a function of ph and kh. If it's the former, cool, right? But if it's the latter, should I be using distilled water with a kh of 4? Thanks again, for all your help

Reedfish,
RedSea are assuming that the only acid in your aquarium water is carbonic and that your aquarium water is 4dkH. I think that most all of the reagents are typically Bromothymol Blue. The reagent doesn't care about the source of the acid or base in the solution it is measuring, it just turns color based on the pH in the solution. As discussed previously the color range will depend on the kH in the sampling water. As long as you use 4dkH water you will have an accurate and more importantly, consistent pH measurement of the sample.

Again, as discussed in previous posts the CO2/pH/kH relationship can only be observed properly if the sampling water has no "contaminants" that would affect the pH reading. That's why using tank water is never a good idea. In fact, if you think about it, why would you even need to buy a drop checker if using tank water were valid? all you would ever need to do would be to measure the pH and kH in your tank and use the chart to determine the CO2. It's precisely because the tank water is unreliable due to dissolved acids or bases that it's use in the chart is invalidated.

Using the 4dkH distilled water in the checker isolates the sample from any contaminants so that you are sure that any pH changes in that sample can only be as a direct result of the CO2 dissolving into that water sample across the little air bubble that separates the checkers water from the tank water. That's the primary reason that the drop ckeckers color change response is so slow. CO2 has to essentially evaporate from the tank water into the little bubble and then dissolve from the air bubble into the drop checker solution. In the morning, after you've turned on the gas, the checker color is only telling you what the CO2 concentration was an hour or two ago. At some point during the day, the CO2 concentration in the tank arrives at, and stabilizes at it's maximum (injection rate minus evaporation and plant consumption). An hour or so after that, there is an equilibrium of CO2 concentration in the tank, in the bubble and in the checker's water sample. This process may take 4 or 5 hours so you have to be patient with the drop checker and with the adjustment of your bubble rate. If you lose your nerve too early because the color isn't changing fast enough you turn up the gas and a few hours later the fish suffer and the checker turns bright yellow. You see the fish suffer and turn down the gas then the plants may suffer. This is the yo-yo effect edacsac and many others experience. This is often coupled with inaccurate color changes due to use of tank water in the checker. Yo-yo(ing) can often induce algae.

You need to use the drop checker systematically and with patience. Give yourself some time like on a weekend when you are home to observe. Use 4 dkH water. Set your initial bubble rate and observe the color changes throughout the day. Find the maximum stable concentration color and note the time of day it occurred. If that color is too blue make a minor adjustment by increasing the bubble rate and leave it there for another day. Note the maximum again and make another minor adjustment if necessary. Remember that most fish can tolerate a limeade green or even into the yellow if you turn off the gas. You will find that with a covered tank you can turn the gas off 2 or 3 hours before lights off. In the morning the checker may still show in the green. No problem, turn on the gas an hour or two before lights on. If you are patient and methodical, you'll find that you'll consume a lot less gas because your timing will be right. It's much more important that your concentration is up in the morning when lights first go on. In the afternoon the concentration has maxed out and the plants are on cruise control. Nearing the end of the day you can throttle back but there is still plenty of gas dissolved and the plants are beginning to lower their consumption.

If you avoid being mesmerized by the drop checker color changes you will be in a better position to determine the profile of concentration changes that occur and it will enable you to respond methodically instead of impulsively.

Cheers,