oxyguard measurements

[yme]

due the recent threads concerning the oxyguard co2 meter, I decided to do some measurements.

I measured both pH and CO2 level of the tank in the morning, before the CO2 was on.
Then, I switched on the CO2 and let the pH drop 0.2 (approximately) and measured again the CO2.
I put the data in a graph and compared it to calculated CO2 levels, using different KH levels as input.

here is the data:

Extra info:
-pH meter and oxyguard recently calibrated
-oxyguard measures 1 ppm in freshly made RO water.
-I measured the KH of the tank: between 2 and 2.5
-I also calculated the KH of the tank (due to the 50% water exchange per week and the use of 100% RO water reconstituted with sera mineral salt, it should be more or less accurate): 2.7
-So there is a big difference between measured and calculated. I must say that I trust the KH calculation more

summary/conclusions from the graph:
-the slope of the measured CO2 data fits nicely with the slopes of the virtual data.
-0 ppm is indeed 0 ppm.
-thus: if slope and the "0 ppm point" are correct, than it is likely that the CO2 measurements in the tank are also correct.
-the CO2 levels in the tank fit almost perfectly with a KH of 2.8, which is very close to the calculated KH of 2.7.

So, if I measure 65 ppm CO2 in the tank, have a good flow due to the vortech MP20 and have a PAR value of 90-100 umol at the surface, why do I have massive stunting, melting and excessive oedogonium???

greets,

yme

 

[dutchy]

Hi Yme,

Interesting post, I wish I had an Oxyguard...

I know you've tried almost everything and there's not much I can say to help you. The only thing I can do is tell you about my tank so you can make some comparisons.

The tank gets Oedogonium with more PAR than 90 to 100 at the substrate (Which might be related to CO2 levels)
The tank gets Oedogonium when plant growth stagnates (Which happens when CO2 is off)

For CO2 measurement I use a Dennerle dropchecker, which actually has a number relate to a colour. I had to get down to a pH of 6 with a KH of 6 to get @ 40 ppm. On the pH/KH chart that's around 150 ppm. All fish should be dead, but they are doing fine. If I use less CO2, the stunting an melting starts on plants like Ludwigia arcuata and Limnophila hippuridoides and Oedogonium starts to show up again. So how accurate is any reading or measurment? 0,1 off here and there relates to 10 - 20 ppm or more variation. hard to say. But I know that when the melting starts, CO2 is off. If I don't correct, oedogonium is the next stage.

If I correct CO2, Oedogonium almost vanishes as fast as it came, mostly within two weeks accompanied by cleanings and water changes.

Just some experiences....

 

[yme]

hmm.

what I also DO know:

I can push the co2 levels to 100-120 ppm (measured by the oxyguard). But without the vortech, my hyphessobrycon eos are within 5 minutes at the surface. If I don't switch the vortech off, then the fish swim just a bit higher in the watercolumn, Also, the respiration of the SAE is ridiculously fast at 100 ppm. shrimps seem to be oke.
So, although I can keep the animals alive at 100-120 ppm, I don't think it is healthy.

at 60-70 ppm, all the livestock is fine. no stress response at all.

greets,

yme

ps: this is old data. I should redo this "experiment"

 

[Tom Barr]

I think based on the measure, the CO2 should be okay.

I know you have pushed it above 65ppm very commonly, this is about what my 180 Gal and my 120 gal are at according to the same methods.
Some tanks might need more/less, but not that much more/less.

I think there's something else going on.

Since you use 100% RO for water changes, the KH/pH chart should be highly accurate, and your test seem to support that also.

Where is that light measurement taken from?
This is something that I know tends to be less questionable. PAR meters do not go out of whack much and while they need calibrated time to time, some simple tricks can tell you if they are off.

GH/KH issues, sediment type? Certain that the fertilizers are actually what you think they are?
I'd be looking at these also.

 

[yme]

hmmm....

I just redid "the experiment".
I seem to get the pH down to 5.76 before I see the fish at the surface (without the vortech). this corresponds to 143 ppm CO2.
This is a calculated value, because the oxyguard co2 meter does not go beyond 115 ppm. (which is something I did NOT know.)
It took almost 1.5 hour to reach this value! (60 ppm is easily reached within 30 minutes)
when I turn on the vortech, the fish stay down.


@tom:

light is measured with an apogee quantum meter. last weekend I measured 230 and 400 umol at the surface of two other tanks. And I have 100-120 umol at the surface. so, it can be off, but not way way off.

KH/GH issues? the calculated values are not really well corresponding to the measured values.
KH: 2,7 calculated. 2.3 measured. I know for sure that the KH can not be below 2.2, for sure.
GH: 4 calculated. 6 measured. According to the calculated values the water should contain: 8.5 ppm Mg, 32 ppm Ca.

substrate: plain flourite black.

as traces I add now DAILY 15 ml TMG, 15 ml flourish and 10 ml flourish iron.
PO4: at least 2 ppm. add 1 ppm every other day.
NO3: 20-30 ppm. add 3 ppm daily.

greets,

yme

 

[Tom Barr]

light is measured with an apogee quantum meter. last weekend I measured 230 and 400 umol at the surface of two other tanks. And I have 100-120 umol at the surface. so, it can be off, but not way way off.

100-120umol at the surface is fine.
Likely about 40-50 on the sediment since you tank is about 50-60cm deep.

KH/GH issues? the calculated values are not really well corresponding to the measured values.
KH: 2,7 calculated. 2.3 measured. I know for sure that the KH can not be below 2.2, for sure.
GH: 4 calculated. 6 measured. According to the calculated values the water should contain: 8.5 ppm Mg, 32 ppm Ca.

substrate: plain flourite black.

as traces I add now DAILY 15 ml TMG, 15 ml flourish and 10 ml flourish iron.
PO4: at least 2 ppm. add 1 ppm every other day.
NO3: 20-30 ppm. add 3 ppm daily.

greets,

yme

How often do you clean the filter? Does the tank look better before/after filter cleanings?
If you have a little high KH/GH that the calculated, that seems okay to me.

It's been awhile, but what type of filter do you have on this tank and how are you adding the CO2?

 

[yme]

Likely about 40-50 on the sediment since you tank is about 50-60cm deep

correct. although the front corners only get 20 umol.

It's been awhile, but what type of filter do you have on this tank and how are you adding the CO2?

I use two canister filters: 1x eheim professional 2 and 1x eheim professional 3. 750 l/h and 950 l/h, respectively.

I clean each filter every two weeks. So one pump each week. the filters are then already a bit dirty. As does the tank. Due to the stunting, melting etc, the tank does not look clean, but rather dirty.

CO2 is added by an aqua medic external co2 reactor, connected to a separate booster pump. I made two co2 outlets, just above the substrate in both front corners.
I removed the ceramic discs that I used for the misting. It didn't do anything, apart emptying my 10 kilo CO2 tank within a couple of week. It was just too expensive

greets,

yme

ps: what about the possibility that the plants really need 100-150 ppm CO2? I still believe my CO2 readings are more or less reliable. But since I do have stunting, melting, oedogonium... as well as quite a lot of green spot algae on older leaves, despite a PO4 level that is at least 2 ppm....

still looks like CO2 issues, right?

 

[dutchy]

....

still looks like CO2 issues, right?

That was what I was trying to say yesterday (although that doesn't mean necessarily that I'm right...) A certain Tom on this forum tought me to look at my plants and throw away measuring devices because it will just make you go wrong, and use fish as a CO2 indicator. That's what I do.

I don't have stunting, melting and oedogonium, but I know what's wrong when it happens.

I do believe my tank has high CO2, 2 modified AM1000's with two 500 gph pumps are working hard to keep up.

Measuring with a single device is still a single point of failure. Can you also make a measurement with the lights off? Can't it be that the EM field offsets the measurement? I've seen this happen with pH controllers.

 

[yme]

That was what I was trying to say yesterday

and that was what made me think and post this reply. especially the oedogonium part. does it also grow on the front glass?

I do believe my tank has high CO2, 2 modified AM1000's with two 500 gph pumps are working hard to keep up.

this suggests high CO2 to me. I can get very easily 60 ppm in my tank with just a single AM1000. but getting the 143 ppm took a lot of time.
I would not be surprised if your CO2 levels are indeed over 100 ppm. I think I should measure your CO2 level....

The measurements were done when the lights were off. luckily, it doesn't matter whether the lights are on or off. both pH and CO2 readings don't change.

greets,

yme

 

[dutchy]

..... especially the oedogonium part. does it also grow on the front glass?

Yep. But it uses GDA as a base to grow on. Without the GDA the surface seems to be too slick to make the algae attach.

.....
I think I should measure your CO2 level....

Maybe better not. That just starts me to change things when it's working well.

 

[dutchy]

...but if you want to make a measurement in my tank you're invited to do so.

 

[yme]

I think that would be a good idea. Although I don't know when and how. I am quite busy at the moment.

Anyway, for the co2 part: I am curious whether these ridiculous high co2 levels are beneficial. So I am still aiming for a pH of 5.74 (=150 ppm co2). It took the CO2 reactor almost 6 hours!!! to reach this pH. Of course, I now left the vortech on and I don't see differences in behavior of the fish or shrimps. maybe, the SAE dos show increased ventilation, but I am not sure. really, really weird.
could it be that people that say "the co2 level is 100-200 ppm according to the pH/KH chart" actually have such high levels??
I don't know.

Anyway, I think I will keep this pH/co2 level for two weeks and see what happens.

greets,

yme

 

[Tom Barr]

I think that would be a good idea. Although I don't know when and how. I am quite busy at the moment.

Anyway, for the co2 part: I am curious whether these ridiculous high co2 levels are beneficial. So I am still aiming for a pH of 5.74 (=150 ppm co2). It took the CO2 reactor almost 6 hours!!! to reach this pH. Of course, I now left the vortech on and I don't see differences in behavior of the fish or shrimps. maybe, the SAE dos show increased ventilation, but I am not sure. really, really weird.
could it be that people that say "the co2 level is 100-200 ppm according to the pH/KH chart" actually have such high levels??
I don't know.

Anyway, I think I will keep this pH/co2 level for two weeks and see what happens.

greets,

yme

If the livestock are fine at this levele, it's worth while to keep it.

I recall a group of hobbyists I went to give a talk to, all had according to the pH/KH chart.........about 200ppm CO2, but fish and plants all looked nice, they'd not really paid much attention to it.

 

[Florin Ilia]

Thanks for sharing and I hope you get rid of the problems soon.

I put the data in a graph and compared it to calculated CO2 levels, using different KH levels as input.

What formula did you use to calculate the theoretical CO2 level?

 

[yme]

If the livestock are fine at this levele, it's worth while to keep it.

so far, I don't see health issues. So yes: I will keep the 150 ppm for 2 weeks. If things don't improve, then CO2 is not the issue.
or at least, that would be my conclusion

The only thing I do notice is that the co2 levels in the morning are now 15 ppm, instead of 7 ppm. the degassing is not that fast...

What formula did you use to calculate the theoretical CO2 level?

CO2=(3*KH)*10^(7-pH)

just from the following website:

http://www.fishfriend.com/aquarium_co2_calculator.html

also interesting, although the website is in dutch: a pH KH calculator that takes in account the testing error:

http://www.aquariumhobby.nl/zoetwater/calculators/co2calc.html

greets,

yme

 

[Florin Ilia]

Thanks, that's the same formula I used. I asked because in the meantime I found other formulas floating around the net (e.g. http://www.aquaterraria.com/en/quimica-del-agua-dulce/747-formula-ph-kh-co2.html#post5356 ).

 

[hani]

Hi yme,
am no expert, but have you tried to float some of the plants for a week or so, see if they grow any different.? i had a similar problem in one of my tank, did every thing possible still stunting, i noticed when a plant float was growing better, cant explain it , i ended up changing my substrate ( flourish to AS), then every thing was back in order. i had luck with flourish before, but i cant tell you why it did not work that time. good luck

 

[yme]

I found other formulas floating around

I wasn't aware. thanks. of course, it makes sense. the pKz is temperature dependent.

am no expert, but have you tried to float some of the plants for a week or so, see if they grow any different.?

yep. if the growing tip is at or above the surface, it grows better. (co2 from the air?)

for the CO2 measurements:

this morning, before the lights were on, I saw 1 BIG amano on it's side. putting the critter in a small tank with an airstone helped within 5 minutes. thus, co2 is too high.
however, yesterday the pH was lower at the end of the day and then everything was fine. so there is likely lees O2 in the tank.

would an oxidator help? and can you fill it with 30% H2O2?

btw: the co2 level should be around 160 ppm.

greets,

yme

 

[cdwill]

I also calculated the KH of the tank (due to the 50% water exchange per week and the use of 100% RO water reconstituted with sera mineral salt, it should be more or less accurate): 2.7

Had you also tested the KH and GH of your R/O water? If the filter mediums/membrane are dirty or damaged, the unit may not be filtering everything out, and these values may not be what you think they are. This may not solve the mystery, but at least you'd have comparison data to compare against your tank water tests, and you'd know that your R/O unit is working correctly.

Another thought: is your tank lighting the only source of light that hits the tank at all times during the day and night, or could there be another light source (e.g. sunlight) that is affecting the amount of light reaching the tank, which wouldn't be captured by the PAR meter?

 

[yme]

Had you also tested the KH and GH of your R/O water?

conductivity is 15 uS/cm.

or could there be another light source (e.g. sunlight) that is affecting the amount of light reaching the tank,

not directly. although the windows are close.

CO2: I found a dead amano this morning :-(
So CO2 is definitely too high.

What to do?

-of course I now lowered the co2 level....
-will an oxidator help?
-will adding excel help?
And since everything is fine when the plants are producing oxygen... too little oxygen seems the problem.
I do think that this co2 level is borderline too high. So I would love to keep the same co2 levels, but change the system in such a way that the critters stay alive and happy.

greets,

yme