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Discussion Starter · #1 ·
Need some advice here, I have a heavily planted 30G tank w/pressurized CO2/w PH monitor and ~4.3W/G of light. My water parameters are as follows:

Nitrate-20ppm
Nitrite-0ppm
GH - ~300ppm
KH - ~300ppm
PH - 6.8

According to the CO2 calculator that means I have something like 80ppm CO2 which is ridiculously high. If I want to get down to around 20ppm CO2 the target PH should be around 7.3. Of course after a week with my PH monitor set to go on at 7.3 the PH is till hovering around 6.8. Should I be trying to soften my water or should I try to raise my PH, or both?!

Thanks in advance.
 

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Yeah I'm curious too, according to my SMS PH probe with a pH of 6.4 and a kH of 10, my CO2 should be at toxic levels.

But my drop checker reads green and the fish seem fine.
 

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Drop checkers do take alot of the calculation BS out of the mix. Ultimatly if you are pumping too much CO2 into the tank the fish are going to show it. But Dropcheckers make it easy to get a good general idea where your CO2 levels are at a glance. Without having to break out your calculator.

Mine came in handy the other day when I changed how my filters spray bar was aiming. wound up outgassing alot of co2 that way. A couple simple adjustments to the bar problem solved. without pumping more co2 into the tank. and without having to break out the calc and scratch paper.
 

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Discussion Starter · #8 ·
I checked my tap water (after it sat around in a bottle for two days) the readings were:

GH - ~300ppm
KH - ~300ppm
PH - ~7.8

Very hard water I know. I'll get a drop checker tomorrow to see my CO2 ppm. Fish generally seem fine. I do see them kind of gasping in the morning, but they are not at the surface, they stay at the bottom gasping with their mouths but still go about their usual business. PH monitor is still set at 7.3, which essentially means it never turns on my CO2 (my PH hovers around 6.8). I do not see much pearling either, though plants seem to be growing, albeit slowly.
 

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How much more accurate is a drop check?.. Maybe by +-5ppm of co2?...


If your fish isn't breathing hard at the surface, you're fine.
Turn down your CO2 slowly, see what happens. The PH should go down but if not, something else is affecting the PH.
My tank's CO2

via drop checker: ~30ppm
via pH/KH : ~140ppm

There is a fairly substantial difference. Also, I find my fish don't really gasp due to CO2 so much as O2 issues. My fish act drunk when I bump the CO2 up even a little bit from where it is now.
 

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There is a fairly substantial difference. Also, I find my fish don't really gasp due to CO2 so much as O2 issues. My fish act drunk when I bump the CO2 up even a little bit from where it is now.
ha.. that's interesting.. THat's how we react to carbon monoxide.
 

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So...I got a drop-checker from BlackSunshine, and after a day the regent is yellow (too high). That's yellow, when comparing to the white center post of the DC....---BUT, NO FISH ARE GASPING AT THE TOP OR BOTTOM OF THE TANK...no abnormal behavior...so what gives????

My ph is 6.9 (says the Milwaukee controller w/ the 10lb co2 tank)
My last tests say this (given the validity of AP tests in question)
Gh: 11
Kh: 18
Nitrate: 20ppm
Phosphate: 0.5ppm

Why does the 'math' of my CO2 and the DC say its high, but no problems that I can see?

I also don't understand how I'm supposed to lower the pH (which is ~7.5 from the tap) without using the pressurized CO2...which is giving me these high co2 readings...

dazed and confused in newbie tank land....
 

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oh..I'm dead serious, none of the fish are acting weird at all, had most of them in there for 2-3 months now, plants in there most of the time, the co2 system is only 2-3 weeks old though....but really the fish are acting completely normal, the plants are growing awesome, I'm just a bit confused about the high co2, the math says w/ kh of 18 and ph of 6.9 I'd be from 60-80ppm of CO2....which 30ppm is what I'm told to shoot for, but I don't see any negative effects, and I don't know how to lower the pH w/o the co2...

2.4w/g lights are on for 8 hours a day...
 

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KBOT, it reads like you are so set on lowering your pH, why?
Ok, first Did you use tank water in your drop checker, or a set kh solution?
Now, the math only works if there is nothing else in your water buffering the pH, hence the drop checkers with a set solution. My tank has a pH of 6.6, and a kH of 8 which is also in the 60 range, yet the drop checker is telling 30ppm.
 

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Taz...no "buffers" like AquaSol or etc...The only thing in there is some Kent micronutrient fluid, and some API "Stress Coat" (to neutralize chloramines & chlorine during water changes) but I don't think either of those are considered pH buffers, correct?

The regent is the fluid that BlackSunshine shipped w/ his drop-checker kit...
http://www.plantedtank.net/forums/swap-n-shop/44423-fs-co2-drop-checkers.html

I'm not sure what you mean "so set to lower my pH"...I thought that was the whole point of pressurized co2, lower ph makes the co2 in a more readily available form (ie, co2 changes into a more non-absorbable form at higher ph). Plus, lower pH is good for my plecos/petricola/amano & crystal red shrimp, and I thought would help to bring down my gH and kH too?
 

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A drop checker can be a heck of a lot more accurate than testing your tank water if there is ANY contaminants from your driftwood, substrate, rocks, chemicals added, tap water. Much more than +/- 5 ppm better.

A drop checker takes ALL of the mystery out of your CO2 levels because it measures the pH against a solution of known kH so there is very little error and it is not thrown off no matter how much crap is in your water.

Thats my understanding anyways.
 

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And in my limited experience i have never heard of a pH of 7.4 being to high for CO2 utilization by the plants. Actually i have never heard of CO2 changing form at any pH. I though we were adding CO2 for the plants to utilize for photosythesis not to lower pH. The lowering of the pH i just a lucky by product that allows us to get an idea of our CO2 levels when compared against the kH.

But like i said someone else might want to tackle this one because i also am just starting out.
 

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Loyal, I think you covered most if it, but I was already typing this before I had to walk away.


NBOT,
It was just that you mentioned lowering your pH several times in your earlier posts.

As far as buffers it's not necessarily something you are adding that can buffer the water, throwing the math off, it can be something in your tap water or something like crushed coral in your substrate that can throw off the math.
No for the drop checker color, I'm not sure what BS uses with his DCs, hopefully he can chime in on the color change, but if you fish are acting fine, no gasping at the surface, or acting strange, lethargic, drunk you should be OK.

I think you are mixing up the relationship. The more CO2 you have in the water the more it lowers your water's pH from it's natural state.

If your water is naturally 7.6, and you add pH down (some form of mild acid), your pH has dropped, but there has been no CO2 added to the water.


To the best of My knowledge (hopefully one of the serious plant folk can correct me if I am wrong) a lower pH does not make the carbon more absorbable to the plants (though it does help to make Ammonia less toxic).
The whole point of pressurized CO2 for most of us here is to provide Carbon to your plants so that they can photosynthesize.

HTH
 

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I'll have to find where I read it...but carbon is in a more readily absorbed form at a lower pH. When the pH is higher, the carbon transforms into a form that *most* plants cannot absorb, except ALGAE and "hardy" plants. That's why people tell new hobbyists to get "hardy" plants if they don't have co2 systems.

The problem is two-fold if I remember...when a plant utilizes carbon, the byproduct raises the pH somehow, making whatever carbon was still remaining in a form that isn't as readily available to plants...that's why you have to keep pumping in more co2...

I'll go search around for a reference....but it had to do the "state" of carbon, which is related to ph & kh, ie, if the carbon was bicarbonate, carbonate, or dissolved CO2...Co2 was "dissolved" (read: absorbable by most plants) at ph (lets say ph6-7), but over 7 turned into carbonate and was really only absorbable by "hardy" plants and algae. I'm sure I butchered this, but that's my basic understanding of it, and why you need CO2 to lower the pH, so that the CO2 is more readily available to the plants in a dissolved form...([edit]this last paragraph isn't exactly accurate, but I'm leaving it in here I don't know why, see below for what I was trying to say here[/edit])
 

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Ok, here's where I read the relationship between pH and the absorb-ability of co2 for plants. I know AZGarden isn't quite a scientific authority, but yes I am assuming what they say is accurate. At any rate, what they say about the relationship of dissolved carbons and carbonate/bicarbonate I think helps explain to a newb like me why CO2 was so important...CO2's form changes depending on the Ph (and temperature apparently, but that's another story). When the pH is in a plant friendly range (~6.4-7.2), the carbon is available more in a "dissolved" form, which plants can utilize. When the pH is higher than that, the carbon is in a bicarbonate form, which is difficult for most plants to use...however, algae and "hardy" plants can use it easily (by "hardy" I mean plants that are true water plants and can use Co2 in its bicarbonate form...which in layman's terms is what the LFS is trying to tell you I think when they say a plant is hardy). This is a problem for us planted tank enthusiasts. The problem is exagerrated, when the "hardy" plants and aglae use what Co2 is available to them, which reduces the Co2 in the water column and INCREASES the pH, which makes whatever Co2 is still left, in a more un-absorbable form!

http://www.azgardens.com/newCO22.php

CO2 Equilibrium

CO2 gas dissolved in water can take the form of bicarbonate or carbonate. These three forms are in chemical equilibrium. Which form is present in what amount depends on the pH.

Dissolved CO2 <=> bicarbonate ion <=> carbonate ion

In the pH range favorable to water plants, pH 6.4-7.2, a percentage will be present as dissolved CO2 and the rest as bicarbonate ions.

From pH 8.0 to pH 8.8 there will be almost no dissolved CO2, a large amount of bicarbonate and a small amount of carbonate.

Although they are named "water plants", most aquarium plants are really swamp plants that grow in their natural habitat with at least part of their leaves above the water line. Therefore, they have adapted to take up gaseous CO2 from the atmosphere. In the aquarium, placed under water, they are only able to use dissolved CO2. Several real water plants, meaning species, which are always under water in their natural habitat, are capable of also using the bicarbonate ion if CO2 availability is limited. It is not however favorable to allow this to happen, firstly because many other plants in the aquarium will be unable to grow. Secondly, with the use of bicarbonate ions the pH will rise to unacceptable levels for all plants.

Because of the CO2 equilibrium discussed, the maximum amount of dissolved CO2 present is dependent on the pH. The lower the pH the more CO2 present.

Since plants use CO2 in considerable amounts, they increase the pH at the same time. Thus the pH value and the CO2 concentration are interrelated (This last sentence is the kicker...when a plant "uses" CO2 then it is no longer available, so the pH raises...when the pH raises, the 'form' of the carbon becomes less absorb-able...that's why you have to keep pumping in Co2, so that the pH stays lower so that the carbon is in an absorb-able form....).
 

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NBot, thanks for posting that.
Always still learning. I'm no chemist, or aquatic horticulturist, but I did a quick Google on "carbon Dioxide uptake pH relationship, and came up with Roger Miller (dislcalimer: this is from back in 98, so I'm not sure if it is still relevant, or has been disputed. ) post in Fins here:
but here is the snipet:
Roger Miller said:
To the best of my knowledge, the uptake of CO2 by plants isn't a pH
dependent process. If you have 15 ppm CO2 then plants will use CO2 no
matter whether there is such a huge alkalinity that the pH is 8.4, or
whether the alkalinity is lower and the pH is 6.8. No diff. Normally,
though the alkalinity isn't that high and a pH of 8.4 implies a pretty
low CO2 concentration.
 
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