CO2 Formula: Does this sound right?

[dsilvers]

We got a great book on aquarium plants. We were reading about CO2 and it gave a formula. You find out your pH, which we had a kit for, it's 7.1ish, then you find out your carbonate hardness KH, which for our 20 gal was 6. Then using their handy dandy chart you find out CO2 milligrams/quart. Which we eyeballed at around 11. So we multipled that times 80 quarts (20 gals) and got .88 grams of CO2. They say for a 25 gallon you should have approx. 1 gram. I did a little math and figured for a 20 gallon you should have around .8 grams. So we figured YAY , not far off. We are doing well. Then I decided to dig a little deeper. I figured out the pH/KH values for EACH decimal of pH from 6.0-7.2 instead of what they had which was numbers for 7.1, 6.7, 6.2...you get the idea. So now...that makes our number on the chart 15.25, i think that's what it was.
Either way, we are now around 1.22 grams for 20 gallons. Does ANY of this make sense to anyone and how are we doing? We JUST did the most recent ampule on the 6th (they last 16 days) and the book says to test every 14 days...which we plan to do. I think it's working. And we looked at some CO2 equipment and it seems so bulky...

 

[Biggen]

Never done it the gram way. It is easier to measure CO2 in ppm or mg/L. Go http://www.thekrib.com/Plants/CO2/kh-ph-co2-chart.html for a handy dandy chart. Plants need between 10-20 ppm of CO2 for optimal growth. Just see where your kH and pH intersect and it will tell you approx how much CO2 is dissolved in your water.

This shouldn't be taken as the "end all be all" either. Your dissolved CO2 will depend on how much surface agitation or aeration your tank has in it. But as a rule, this chart is a good guide.

 

[dsilvers]

Thank you! I will check out that chart. We are trying to have the most understanding possible of how our tank works. We know our pH is good. That the fish are happy. the plants look good, and now we have a rich substrate, good lighting and we use Plant Gro for freshwater plants...SO...we are thinking we are on the right track. I will check out that chart righ tnow. Thanks!!

 

[dsilvers]

LOOKs like it's 22. With KH at 6 and pH at 7.1...so that seems ok?

 

[dsilvers]

Oh wait...if the pH lines are constant and according the quick reference down below the chart...we are at 14?

 

[Biggen]

Yep, 14 ppm CO2. Pretty good for plants...

 

[dsilvers]

Oh I am so happy! One more thing, thank you for your help so far, i appreciate it--do you find that a lot of these test kits are sort of like a guessing game. Our pH test kit you just do the little vial of water, add two drops of the pH tester and then hold it against the color/value chart. So it COULD be 7.1, could be a bit closer to 7. Then with the KH kit, which we just got, we've used the pH one for a while, you count the drops you add until the water goes from blue to yellow? The number of drops is your KH? Are there more accurate testers available??

 

[Biggen]

Argh!!! I hate most testing kits!!

Yes they do make digital pH meters, but I think the expense outweighs the benefits of it. Besides, for the hobby, I really don't need a precise reading. I watch ebay every now and then to see if I see a cheap one for sale. So far, I haven't...

Not sure if they make digital kH kits or not. But again, really don't need to be precise. You just really need to get in the ballpark.

When using the kH test kit, what ever number of drop the water changes to bright yellow is the degrees of kH you have. For example if it turns yellow on the very first drop, than you have ~1 degree of kH, possibly even less. If it turn bright yellow on the 5th drop then you have ~5 degrees of kH, etc...

One more thing, thank you for your help so far, i appreciate it

No problem. I love doing it. Besides it gets me away from work for a while...

 

[dsilvers]

Right...that's how we got 6 as our KH. It was blue, blue BAM yellow on the 6th drop. So ok, we were doing that right. It was like being back in chem in college. And with the pH, we eyeball it. As long as it isn't seriously light green (aciding on our test) or majorly blue (way too basic on our test) then we are happy. Most of the time it ranges from 7.0 -7.2 Depends on the water changing schedule. Initially we were water changing happy. Then we quickly learned. It is quite the learning process. We know so much now. I like to research and this hobby certainly needs that. We have a tank calendar now and we do changes at a more normal pace and the water is happier, the fish are active. Our Balas dropped dead after the water changing fiasco. the fish guy at our LFS was like, "SLOW DOWN on the water changes. PLEASE." We were newbies, what can I say.
But this plant stuff...it's almost more difficult than the fish. The plants appear to be doing well. With the fish, for me, I look at them every day, see their behavior. After losing fish initially and learning more about watching them, I can easily tell if someone is unhappy. Who k nows with a plant besides when you come home and it's suddenly become a skeleton. Thankfully that has stopped, but initially we were so disheartened. That was before we knew aquarium salt is not good for plants, that you need CO2, substrate and plant nutrients. We were a mess!