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-   -   A long boring post on PH, CO2, Buffering, plus questions! (

redchigh 02-17-2010 05:50 PM

A long boring post on PH, CO2, Buffering, plus questions!
(Well You might remember a while back that I had trouble (on a different forum) with my Ph being 6. It's a livebearer tank, so of course I was concerned.

I bought some "correct Ph" from wally world, and it totally messed up everything. (my water turned milky white overnight, all fish were at the surface, and 6 died. Also, the PH didn't even change.)

So, I did what I could to save the fish. Did lots of water changes, and increased aeration since the fish were at the top, which to me is a sign they were having trouble breathing.

I got a few suggestions, like calcerous gravels and crushed coral. Unfortunately these were too expensive, so I put some thought into it. Corals and calcerous gravels revolve around calcium carbonate. I knew I'd learned something else that was calcium carbonate... and then I remembered.

After the fish seemed better, I added a stick of chalk. (all in the course of a day- I know, risky, don't get on to me, it's a learning process. Plus I know a PH of 6 bad for gups.

I added the chalk, and the next morning tested PH. It was 7.5. W00t! After much celebrating, I went on with other things. Today, I tested the PH, and it was 6 again. I added more chalk, but wait- No water changes after the last chalk piece, how did it go down? I know nitrates can lower PH so thats what I THOUGHT the problem was.
Turns out I had high co2 levels (explains why I had 10 flower spikes at a time from the aponogeton, and why I lost 5 guppies and my beloved ghost shrimp over the course of 2 weeks)! Levels over 25 are toxic to fish- my best guess now, was my level was somewhere between 40 and 75. I switched out my weakling air pump with a more powerful one, and in 30 minutes my ph went from 6.0 to 6.2. I'm hoping that the oxygen supplementation doesn't prove too shocking for the fish, but in an effort to correct this problem, pretty much my only option is a trial by fire, and see where it goes :-/. IT's a bad idea, sure, but short of standing by the plug and plugging in/unplugging the pump every 20 minutes, I don't think I have any options.

Anyway, still going...

I think I figured out why my water turned white overnight- This is my reasoning.
The PH stable tablets contained a chemical that behaves similiarly to CaCo3, Calcium Carbonate. 24 hours a day, the fish produce CO2. At night, the plants stop absorbing it. I know from Wikipedia these two facts-

Calcium carbonate is poorly soluble in pure water (47 mg/L at normal
atmospheric CO2 partial pressure as shown below).

The equilibrium of its solution is given by the equation (with dissolved
calcium carbonate on the right):

CaCO3 Ca2+ + CO32–
Ksp = 3.7×10−9 to 8.7×10−9 at 25

where the solubility product for [Ca2+][CO32–] is given as anywhere
from Ksp = 3.7×10−9 to Ksp = 8.7×10−9 at 25 °C, depending upon
the data source.[17][18] What the equation means is that the product of
molar concentration of calcium ions (moles of dissolved Ca2+ per liter
of solution) with the molar concentration of dissolved CO32– cannot
exceed the value of Ksp.
Which , I think, basically means that at a certain point of both of them increasing, something has got to give. I don't know the term, but basically, the CaCo3 and Co2 in the water were competing for the same space in between the water molecules. At some point, one of the guppies inhaled, and exhaled that one extra bit of Co@ that broke the camels back. (It's funny to imagine, inhale, exhale, then suddenly POOF all this white stuff appears. Doubt it was that sudden though)

The CaCo3 (or similiar compound) was forced out of the H20, and into the "water". (ie, it wasn't really dissolved anymore, rather tiny tiny particles were drifting in the water which made the water look cloudy. Also, it's why, when I increased aeration and did a 50% water change, the residue that was left finally dissappeared (dissolved back into the water). Right now, I'm out of test strips so I can only test PH. However, CaC03 dissolves in acidic water, and is relatively stable in base water...

So I'm going to leave the chalk in, and test the PH to make sure it doesn't get too high, so the chalk will be a sort of "insurance policy" if there's a power outage or something. It's just setting on the substrate, so I can take it out easily. (worst case scenario, I don't monitor it, and the chalk dissolves into it's max concentration for dissolved water, placing the PH at 8.7. However, since CaCo3 only dissolves at a rate similiar to it's decomposition rate, I highly highly doubt the PH would go above 7.4-7.8, as long as it's away from direct water flow and I don't force it to dissolve.

Argh, I forgot my questions... Oh, that's rihgt. If someone was using CO2 supplementation in a heavily planted tank (knowing exactly how much CO2, and keeping the CO2 levels the roughly the same, and at a relatively low setting) does anyone know if CaCo3 would keep the PH from fluctuating, at all? Basically, my goal right now, is to get my PH to 7.4, and Kh at 10-12, giving me a CO2 level of approx 12-15 ppm.

If you don't know, can you at least agree that 7.4 ph and Kh of 10-12 are good for gups?
If it seems overly complicated, it's not. It's the same as using calcerous gravel or crushed coral, just in a much cheaper (and purer) form. (chalk is 99 cents for enough to last me a long time if I resist drawing with it. :))

Wikipedia-CALCIUM CARBONATE Calcium carbonate - Wikipedia, the free encyclopedia

Measuring CO@ levels in a planted tank- Copyright 2000, Chuck Gadd- Measuring CO2 levels in a Planted Tank

(maybe this will help someone. I know it would have helped me two weeks ago)

Mean Harri 02-17-2010 06:40 PM

I find it odd that more than 20ppm co2 is harmful because all the co2 drop checker guys set theirs at 30 ppm.

Angel079 02-17-2010 06:52 PM

Let's break this down some get to the bottom of the cause and fix it for good there in your tank.

What's the tap pH and KH? What is it in your tank now?

If crushed coral if too expensive take yourself tot he home store close by in the section where they have all the gravel, bricks etc there's stuff that looks like gray fine gravel mix with lil red pebbles in it I can't remember Lows brand name for it but it looks like I said and it used under installing paves for your sidewalk etc its like $3 for a 25lbs bag and you'll need maybe 1/2 cup if not less dep on your tank size; then when it wear's down add a lil more so a 25lbs bag will last you forever and there's no other chems but rock materials in there so it won't hurt no fishy's.

Mean Harri 02-17-2010 08:02 PM

I started giving this another read. All those fancy little symbol things in that equation give me a headache. I sucked at math. So when I have a little less ADD I'll try getting in to this and coming to understand it.

redchigh 02-17-2010 08:35 PM


Originally Posted by Mean Harri (Post 327774)
I started giving this another read. All those fancy little symbol things in that equation give me a headache. I sucked at math. So when I have a little less ADD I'll try getting in to this and coming to understand it.

You can skip that part. it's the chemistry-ese.

And angel I think the chalk will work equally well. It doesn't dissolve hardly at all, and the PH has slowed a LOT.
The PH out of the tap is 6.0, and when I let it sit overnight it goes to 6.9. Also extremely soft.

I live in an apt with tiny closets- a bag of gravel would likely take up half the closet. I only have two ten gallons, and in my apartment, they seem big. I don't think I'd have room for a 40 gallon if it was free.

Right now, my tank Kh is "good" at around 5.0- my tap water is around .2. My PH is unknown because I can't find the little vial. I'll mention it when I find it.

Also mean harri mentioned that some people set their CO2 to 30 ppm. I'm not sure on this, but I think that if the table says, for example, you have 10ppm, but your tank is heavily planted, well lit, and fertilised, the plants will lower the CO2 content. Maybe by shooting for 30, they have less than that in their water column... not sure...
I'm sure it also depends on the fish. After looking it up again, when the water turned white and all the guppies were in the upper inch of the tank, my CO2 was over 100 ppm. (The chemical I added bumped up the hardness a LOT, and the PH stayed the same.)

Mean Harri 02-17-2010 09:11 PM

In reading Chuck's page on co2 it appears that the kh does not affect the co2 levels directly.
When you oxygenated the tank with the air pump you gassed out co2 which will allow ph to rise. co2 lowers ph and with your high co2 readings it's a no-wonder you ph was 6
So to answer your question. I would say no. CaCO3 relationship with co2 is affected if kh is less than 1 degree as stated by Chuck.

Angel079 02-17-2010 09:33 PM

Never dealt with chalk so far so I can't talk about it. Main thing (just like anything else used) you do NOT wanna have swings like this 6.8-6-7.5-....on your fish that's VERY stressful / sickening to them. So test and see how its dissolving daily.

Alright so for stars I'd wanna prep my tank water in buckets 1 day prior to when doing the water exchange in that case.
You're saying kH "good"...What are you measuring with? Sounds like you're using test strips - I hope not do you? These strips are as good as me looking at your tank and guessing so totally NOT useful for what you're doing there tempering with the water. If you don't have the money to buy a full kit at least buy yourself a liquid KH & pH test kit for right now for like $10 total pleaseee.

What do you have inside the tank others then fish & plants? Do you run air stone with he plants? Large new driftwood in there?

For right now I'd not even worry with that co2 matter - I'd worry on stabilizing that tank for the fish (I"m assuming livebearer tank) you have there! With a decent amount fish you'll have no worry about co2 supply for the plants anyway!

And pls be super careful with these ph up/down style chems; they can wack your stock out in no time if used wrong and they will permanently expose your fish to these up-down fluctuations!

Claudia1002 02-17-2010 11:21 PM

If you have soft water and are supplementing CO2, then you're going to have some problems with pH fluctuations.
You need to get a test for KH and pH and probably GH.
Then consider this cheap fertilizer made to boost the hardness of your water. You buy it dry and mix in water.
Planted Aquarium Fertilizer - Dry Fertilizers, Dry Fertilizers, Planted Aquarium Fertilizer - Barrs GH Booster, Barrs GH Booster,

You'll need to know what your KH and GH level is first, then monitor after you dose until you get a good idea of how to dose your particular water.

redchigh 02-18-2010 09:29 AM

I may not have been clear... right now I'm not supplementing CO2. I just calculated my CO2 using the chart.

I'm not sure, but I think maybe the chart doesn't tell you exactly how much CO2 you have, but rather the maximum amount that can be dissolved? I have no idea.

According to the chart though, lowering your KH would somehow magically add CO2 to your water.

Right now I do have an airstone attached to an air pump, and the PH is not swingling nearly as wildy as I thought. It did raise by .2 degrees in about an hour, but now, checking it the next day, it's 6.4. I think it's climbing slow enough to not harm the fish... Don't you think?

and yes, I have test strips. I get paid tomorrow, and I plan on buying the "Tetra Laborrett Water Test Kit".
The test will test for:
Freshwater PH
Carbonate and general hardness
Nitrite ammonia
is that good? If there anything else I need to test for?

Angel079 02-18-2010 10:36 AM

Yea I had that tester yrs ago it'll do you just fine.

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