Hello, at present in my tank are ph:6.1 and dkh:5º,it a lot of co2??According to the tables I have 93 mg/l of co2, the fishes do not gape, can it be possible??? tank 99gal. Why does he be recommended to always 30 ppm?? For the fishes?? If it be possible to increase the concentration of co2, serious bad guy for the plants so much co2??Thanks..

Is it possible that your test kit gave you wrong results? I had to learn at this site, that most test kits are not very good or to say it more clear they are not worth the money.
Since I switched to checking my CO2 with a KH-reference solution and a drop checker, I feel much more confident about my CO2 in the tank. There is a lot of info on using a drop checker with the kh-ref. at this site.

Robin

I'm satisfied that the test kits I use are close enough to "the truth" when water chemistry is within normal ranges. (And, no, I haven't calibrated them, but the readings are consistent over time and with different batches of test kits.)

I do wonder, though, what is the "optimum" CO2 level in a high light tank. Are there any experiments that quantify the differences between, say, 15 ppm and 50 ppm?

I suspect that there isn't a lot of difference, but I really don't know.

Bill

I based my range on a couple of things, one is practical experience, the other is a paper by Van et al, 1976.

The maximum CO2 levels for growth under any lighting situation is about 30-40ppm for 3 submersed aquatic weeds.

As they are weeds, they will use more nutrients.grow faster etc than most other plants.

As long as all the plants are getting plenty of CO2 at this range at the surfaces, then there will be no issues.

Current plays a huge role and the boundary layers etc around the leaf, leaf shape etc, but that's a pretty good average range.

I arrived at this long before I read the paper, and most suggested 10-15ppm prior.

Regards,
Tom Barr

Yes, Van et al 1976 dicussed this in detail over a wide range of light intensities.
They found that the 3 aquatic weeds saturate at about 600micromoles of light and about 30-40ppm of CO2.

Fun tropical midday sun = 2000micromoles

Adding more does not increase photosysnythesis.
Some plants may have species to species differences etc, but this is a good general range.

If you added say 50-70micromoles of light , then 15 ppm is likely fine of CO2.
Which was the case about 10-20 years ago.

Since folks have added more light, now they need more CO2.
If you add good CO2 at low light, then you have excellent growth, healthy, easier to manage/prune etc, dose nutrients, less issues targeting good CO2 levels etc.

If you look at optimal CO2, you need to see in what context with respect to light.
Light drives the CO2, and NO3 etc can regulate CO2 uptake if limiting as can PO4 etc.

Regards,
Tom Barr

Thanks, Tom.

Is there a way to convert micromoles to watts per gallon or some other measurement?

Bill

I think 30-40 ppm, as measured with a drop checker, is about the maximum most fish will tolerate. I'm basing this on my guppies, which often, but not always, cluster at the water surface late in the day, with my drop checker saying 30-40 ppm. My rasboras don't head to the surface at that value, nor do the loaches. But, the one time I let the drop checker get nearly yellow, all of the fish were at the surface and a few guppies died.

I now have the stuff I need to check this more carefully, using two drop checkers with different KH water in them, with reference containers of 6.5 ph buffered water, having the same amount of pH reagent in them. That should let me zero in on the actual ppm pretty accurately. At 3.2 dKH both the pH and KH reference colors should be the same at 30 ppm, and at 5.3 dKH they should be the same at 50 ppm. I should be able to interpolate inbetween those readings. Unfortunately I haven't had the time to do this yet.

It can be known if the tank's dkh is the correct and does he not give false readings?? I have well-read the article to do a solution mother with a kh 4, and thus to taste it, really them kh test do they not measure real alkalinity??

Test kits for KH and pH may be very accurate, but that is not the problem. The table that shows CO2 versus KH and pH is only accurate for water that has only carbonates affecting the KH and only CO2 affecting the acidity. Our aquarium water very often contains phosphates, which affect KH, and tannic acid, from bogwood or decaying plant matter, which affect the acidity. So, the CO2/KH/pH table doesn't give a good reading for how much CO2 is in the water. Unfortunately, the reading it does give is almost always too high, usually much too high.

The drop checker works because it uses distilled or deionized water, with a bit of sodium bicarbonate in it to raise the KH to 4 dKH. That water has nothing else in it to affect KH or pH except the CO2 that mixes into the drop checker water from the tank water, so that the tank and drop checker have the same ppm of CO2. Now, the pH indicator reagent in the drop checker will give an accurate indication of how much CO2 is in the tank water. The reason for using 4dKH as the KH of the drop checker water is because at that KH, with 30 ppm of CO2, the pH will be 6.6, and at 6.6 pH the color will be green, a relatively easy color to judge.

Now then if the ph in the tank this one in 6.2 more than likely is q the kh 5, do not be a real reading, perhaps rather be kh2, in any case comprare a test of co2, I have a good chance to eheim's test.
I check with the distilled- water and sodium bicarbonate mixture ( kh4 ), does result be probably green color or lightly yellow to be the co2 ok??

.Another doubt that I have is the following, if I fulfill the permanent test with distilled water kh4 and the tank's water is REAL kh 2, a ph 6.2 like I have serious ideal and the mixture of kh4 the tank acquires a color giving a lot of co2 to contain a kh ( 4 ) q itself really he does not have . is This possible???
Excuse translation no himself if what I attempt saying gets along well .

Regads..