pH, KH, DH, CO2 and iron

[Allivymar]

Ok, so while I regularly check the pH of my 10g planted tank, I just got around to testing KH, DH, Iron and CO2 levels.

Ph remains steady at 7.0; never seems to fluctuate much at all.

KH is 3 which I gather is a bit low.

DH is 10.

CO2 appears to be 9.0 mg/l which I'm gathering is also a bit low.

Iron is .05 mg/l.

So here are my questions. I'm using that Hagan CO2 thingie with the ladder. Should I move the tubing down to the 30g level? I have it at the recommended 10g level, but it appears the levels of CO2 are low. If I do that, will it affect my KH levels and lower them more? I'm pretty dense when it comes to this part of planted tank care and all the H's confuse me LOL I keep reading, but can't seem to get it to sink into my head.

I'm also adding iron enriched Nutrafin Plant Gro at one capful per week as per directions, but the iron levels are barely readable. I add on Sundays, so it was put in yesterday. Should I add more? Or should I use a different fert?

Lastly, most of my plants don't seem to be suffering at all LOL You can see what I mean here; if you check the dates you'll see most of the pics are only 2 weeks apart: http://www.myaquaria.com/gallery/planted-10g . Should I even bother doing anything? The fish are doing fine as well.

 

[Guest]

Rex may tell you to do something to get the KH up, but I dunnow.

Personally, i woudn't change much. Your plants are obviously doing great, so I don't think you really have to change anything at all. Very good pics.

If it were me though, I would put the co2 tube at the bottom position, and monitor ph. The only reason I would try this is to see if you can get some pearling. That's the one thing I really lve to see in my tanks, can't always get it to happen. Nothing quite like o2 bubbles covering the plants, and rising to the surface in steady streams here and there! JMO.

 

[Allivymar]

Hrmmm, ok. Looks like moving the tube down won't have any negative effects seeing the CO2 levels atm (I get all paranoid about CO2 levels and the fish LOL). But won't it lower the KH levels even more? Or will it raise it; I'm SO lost when it comes to this part of water chemistry LOL

And thanx I figured visual documentation of the tank was the best way to go; hooray for digital cameras! It really demonstrates the growth of the plants vividly. I don't always see the diff since it changes only a little from day to day, but I look at those pics and think, jeez, why can't I get my houseplants to do so well LOL

As for pearling, the only thing that has pearled so far is the Marimo balls. Go figure. It would be cool to see it on the more advanced plants; I'll move the tube when I get home from work tonite

 

[Guest]

I too would run the CO2 tubing to the lowest level. Also your kH is fine at 3. I have to struggle like mad to get my very soft water up to 3 and hold it there. Don't sweat the iron. Consumer level iron test kits are worthless.

 

[Allivymar]

Coolio Thanx Rex. Its nice to have 2 opinions which don't conflict LOL

Will moving the tube change the KH levels? And in what direction? And should I care? LOL

Feh, the iron test is worthless? I had to order it online cause no one around here carries em. I was under the impression one tested to see if the fert levels were good. If the tests are useless, how else would I know? Don't wanna add ferts if there's no point.

 

[BrianNY]

My KH is 2 which really has me concerned about adding CO2. How do you keep the KH up?

 

[Guest]

More CO2 will not effect the kH. But it will lower the pH if the reactor is doing it's job.

BrianNY,

To raise kH you can use baking soda, note baking soda, not baking powder. Or you can use calcium carbonate which will also raise your gH. And I'm sure there are some commercial items you can use to do the same. For ideas on how much to add go to this page http://www.frii.com/~gbooth/AquaticConcepts/ and click on the Water Chemistry link.

 

[Allivymar]

Ok. I think I see where some of my confusion is coming from: KH (hydrogen carbonates) = carbon/hydrogen. CO2 = carbon/oxygen. (My 9th grade chemistry teacher didn't speak english well LOL). So, if I'm understanding a little more correctly, one carbon form isn't necessarily going to affect the other. If anyone can explain more clearly to me I'd appreciate it

Also, I had a thought. I'm using laterite, which supposedly contains a lot of iron. Do I even need the ferts then? Will the iron in the laterite register on an iron test? If so, why would my iron levels be so low (I'm using the Seachem test which is supposed to be one of the better tests on the market).

Lastly, before I change the CO2 tube level, I've read crypts don't do as well with higher levels of CO2, but I can't seem to verify this. Anyone have any info on it? My other plants are doing well at this level of CO2 even if it is low; I don't want to mess up the crypts tho.

 

[jsoong]

Alliv, I am going to try to explain the CO2, HCO3, pH thing. I routinely manipulate these variable in people (as an anesthesiologist), & the chemistry happens to be the same in people as in a fish tank.

OK, everyone know what pH is? It is a measurment of the amount of H+ (Hydrogen ion, or acidity). Neutual water has H+ concentration of 10e-7 eq/liter. To avoid the exponential notation, pH was invented:

pH = -log [H+] .... Thus pH of neutual = 7.

KH is a measurment of your buffering capacity. In fish tank, this is mostly bicarbonates (HCO3-), but there are other buffers involved. What a buffer does is react with excess H+, taking the H+ out of commission. Your buffering system also can generate H+ when there is "not enough". Thus, buffers decrease pH changes in a system.

The HCO3- buffer system invloves CO2. Specifically:

CO2 + H20 -> H2CO3 -> H+ + HCO3-

Simply stated: CO2 added to water will form carbolic acid, which quickly breaks down into H+ & HCO3-.

BTW the reaction can also go backwards. Excess H+ will react with the HCO3-, forming CO2. Thus keeping your pH stable.

Therefore, it is not true that adding CO2 will not change the HCO3- (or KH) level.

However, only a small amount of CO2 will turn into HCO3-. The reaction is govened by the association constant (Ka), and will depend on the pH.

The exact equation (the Henderson-Hasselbach equation) is:

Ka = [HCO3-] x [H+] / [CO2] x [H2O]

The [ ] means concentration of (whatever is in the bracket).

This is the equation used to find the CO2 level by measuring pH (ie [H+]) & KH (ie [HCO3-]).

From this, you can see that increasing CO2 will increase both the H+ level (decreasing pH) and the HCO3- level (increase KH). However, we measure the H+ level in much finer units (10e-7 eq/l) than HCO3- level (usu. measure in 10e-3 eq/l), so we see changes in pH, but the tests are not sensitive enough to pick up the change in HCO3- levels.


I hope I haven't confused anyone. I will try to answer any questions after class.


OH, and there will be an exam later...

 

[TankGirl]

I am with jsoong on this. Before CO2 my aquarium water measured 5dg KH, and after CO2 I am at 4dg, but that is with CO2 at about 15ppm.

Incidentally, my crypts are doing great with the CO2, and babies are coming up all around (foreground center of 55 pics in my gallery). When I had my 10gal planted and used the Hagen I set the tubing at the lowest position and had great results. You could even try running it through your filter intake, but quite honestly if you don't have algae problems or signs of nutrient deficiencies then I would not even do a thing! One look at your tank and you can see the plants are happy!

 

[Allivymar]

Whoa! I retested again after moving the tube down the night before last. I think I have to move it back; I cannot BELIEVE how much its changed the parameters:

GH 10 (the same)
KH 2 (!)
pH between 6.4 and 6.6 (!?)

Thats a BIG jump in pH for such a short period of time; the fish don't seem to be reacting to it but I sure am! It means my CO2 levels are between 15.1 (which is a good thing) and 23.9 (not such a good thing). Thing is, I'm worried about moving it and kicking up the pH back up in such a short period of time; I know pH fluctuations are not good. Should I give it a few days and change it over the weekend? Or just do it ASAP? Or leave it?

Btw jsoong, I need to reread that a coupla times LOL but its starting to sink in; thanx! Have some kudos for helping me out And I'm relieved to hear the crypts are ok TankGirl; mine are doing well and I was worried I was going to kill em! And I am starting to see a little beard/fuzz algae on some of the slower growing plant leaves; I removed em, but the otos don't seem to be interested in it.

 

[Guest]

23.9 is not bad. I try and run my tanks in the 25 ppm range.

 

[Allivymar]

Really Rex? I had read optimum range was 10-20 ppm for CO2; I was worried higher levels could cause probs with the fish. It shouldn't be a problem then?

And what about the pH? I'm sure the neon/cards are loving it, but its definitely lower then my tap (7.0) now that I moved the CO2 tube; I generally change about 20% a week (theres a LOT of oto poo - more then needed for the plants and it looks unsightly). Am I going to have probs next water change with the diff in pH?

And thanx Rex I really appreciate your expertise in this area. Have a coupla kudos

 

[Guest]

I would be more comfortable if you raised the kH. Your water is kind of strange with that high of a gH and that low of a kH. If you need suggestions on how to raise the kH just ask.

 

[Allivymar]

I'm askin LOL I haven't the vaguest idea how to raise kH.

I was pretty surprised at the amount of the drop in both kH and pH. I thought the kH of 3 was a bit low to begin with; 2 is worrisome. I do have a bit of driftwood in the tank which I'd have thought would have at least raised the pH a little or kept it level, but I guess not; theres not a real diff between tap and tank pH prior to the CO2. Never checked tap kH tho...should I? As for it being strange, strange is the story of my life LOL

 

[jsoong]

Talk about strange! I've been scratching my head on why your KH dropped with increasing CO2.

The pH drop is expected when adding CO2. But, for every H+ produced from CO2, there is 1 HCO3- produced. The HCO3- produced would actually *increase* the KH, but not by any measurable amount. (By my calculations the KH would have increased by something like 0.01 degree! ) So I can't figure out why your KH should drop.

If I read your posts correctly, your KH out of the tap is 3, & pH 7.0. This would indicate presence of another buffer. At CO2 level of 3 ppm (in air), pH should be around 7.4-7.6.

Now, if there is another buffer, that buffer may be "knocked out" with a pH change, resulting in loss of KH. In that case the actual CO2 reading can be much higher that results obtained by calculators assuming HCO3- as sole buffer. If I have the water at work I can run a sample in my CO2 analyser ..... :?

As for increasing KH, the simplest is adding Sodium bicarbonate (aka baking soda). Rex can prob give you the exact dose. I read the calculations in some web site but lost the link.

 

[Allivymar]

Auuughhh!

Well, I discovered high levels of CO2 DO cause crypts to melt *cries*. Looked in the tank last nite and one of my crypts is just goo. Boy, they ain't kidding when they describe it as "melting". I moved the CO2 tube back to its original place, and hopefully the crypt will come back. I'm bummed tho. It was a nice plant, and now I have to go into the tank to remove all those icky mooshy leaves too.

You can see what happened here:

 

[TankGirl]

I have had my crypts "melt" from changes in water quality, but mine are doing fine in the high CO2 (fingers crossed, I probably just jinxed them). When mine melted they did not completely die, I just vacuumed up the melted parts and the rest that would not dislodge with the vacuum tube remained and the plant came back. Hope this is not the end of your crypts!

 

[Allivymar]

*sniffle* Thanx TankGirl. I did exactly what you did; vaccumed up the gooey bits and left the stuff that didn't come up the siphon. It was likely the pH change that did them in and not the CO2 (least, thats what I'm thinkin). And strangely enough, if you look closely you'll see it was only ONE crypt plant that keeled; the others are ok. Makes NO sense to me, but since I moved the tube back, hopefully it will come back.