gh/ph/kh balancing - The Planted Tank Forum
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post #1 of 9 (permalink) Old 10-04-2013, 07:59 AM Thread Starter
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gh/ph/kh balancing

Hi[censored]Guys I have a very weird water condition , not getting what to do my water parameters(water before getting into the aquarium) this is the ro treated water
Kh = 1dkh
Ph =7.4
Gh= 14 dgh
Tds= 170
I have a loaded aquarium with plants still no fishes but just a few algae eater coz I am growing hc in it. My main concern is the ph fluctuation which I noticed today morning that was 6.2 and a couple of dead otos . Injecting co2 @ 2bps I am still very confused how to increase the kh without affecting ph and gh of my water .thanks any advice and sugestion are welcome.

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post #2 of 9 (permalink) Old 10-04-2013, 09:24 AM
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Sodium bicarbonate raises just kH. Baking soda used for cooking is the stuff I used and it worked great.

I might want to clarify the fish part because you said no fish in the beginning of your sentence than later on you said a couple of otos dies. Which is it? Fish or no fish?

Also, you sure about that CO2? Your pH seems rather high if you inject CO2 and it's still above 7 with no carbonates in the water.
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post #3 of 9 (permalink) Old 10-04-2013, 10:02 AM Thread Starter
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I had 5 otos now 3 left , ya I am sure bout the co2 injection I have contro soil as a substrate and loads of rocks in the tank that might be keeping the ph but my concern was the fall of ph from 7.4 to 6.2 in just in 12 hour period and thats what I think made the fish die but for now I have switched of the co2 and did 20% water change to get things stable but I want to continue with co2 to let my hc grow but not able to find a right way . My lfs said that adding anyting to raise the kh will also raise the ph of the water and also the ph fluctuates a lot in short spams as I test it with the ph meter

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post #4 of 9 (permalink) Old 10-04-2013, 10:55 AM
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Your substrate could be removing the kh/ph like mine does.
if you use soda, your kh and ph will go up.
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post #5 of 9 (permalink) Old 10-04-2013, 02:12 PM
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Baking soda will raise kH unless there's something in you aquarium removing it. kH will keep your pH from falling too low. The high fluctuation leads me to think you have low kH which is consistent with the readings you posted.

I wouldn't trust your pH reading though. With that low kH the CO2 dosing should not allow the pH to rise that much. It should stay somewhere close to 6.8 during the day and drop to 6.2 during the night.

You dose CO2 constantly or you turn it off at night?
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post #6 of 9 (permalink) Old 10-04-2013, 07:13 PM Thread Starter
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Hey thanx for ur costant reply . I switch off my co2 at night and put on an airstone.

This is what my exact problem is, a very huge ph fluctation right now its 01:00 am and my ph is 7.1 as lights and co2 goes off at 11:30 pm and iam sure its gonno be not more than 6.2 in the morning. Gud nite catch u in the morning with new readings.
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post #7 of 9 (permalink) Old 10-05-2013, 03:11 AM
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A change in ph should not affect your fish if your kh is staying constant. CO2 cause huge fluctuations in ph, on a daily basis and fish are not effected. I would lean more towards a fluctuating kh, or gh, leading to osmotic shock.
Otos, additionally are known for dying after a week or too. Your tank must be very established and a healthy supply of algae they can eat or they will starve. I know some people leave rocks in water to grow algae outside in sunlight and switch them into their tanks for a food source.
After reading ur original post are u remineralizing ur RO water? Baking soda is the way to raise ur KH at water changes but u need to determine if anything in ur tank is removing carbonates.
I dont use ro water and I don't know anything about it but if u r filtering it I would think ur gh would be lower as well. Maybe u need to start buying ro water and remineralizing it, if ur tap water has such high gh.
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post #8 of 9 (permalink) Old 10-05-2013, 03:53 PM
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I had almost 0 carbonates and pH during the day didn't go lower than 6.5 due to photosynthesis. Aerating at night raised my pH so quickly that I only done it for 4 hours since it would raise my pH above 7 if left longer.

I was aiming at a top value of 7 with the low not more than 6.2

I don't think your pH reading is accurate. Or you have some form of organic acid pulling the pH low. Tannins, humic acids and other complex organics like phenols will also affect pH outside of the CO2-carbonates-water relation. Bog wood, leaves and other decaying matter rich in complex organic compounds like aromas and oils can cause that. Peat will lower kH and also gH.
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post #9 of 9 (permalink) Old 10-05-2013, 08:00 PM
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KH- carbonates- stabilizes the pH. Low KH = pH is more free to change, depends on what else is in the tank. Nitrifying bacteria use the carbon in from carbonates. Some substrates remove the KH from the water.

GH- minerals. Calcium & Magnesium. Required nutrients for fish and plants.

pH- a measure of the amount of H+ compared to the OH- in the water. Some materials latch onto one or the other of these, leaving an excess of the other.
carbonate tends to soak up the H+, so OH- remains. This is alkaline water.
Peat moss and many organic processed produce more H+. This is acidic water.

Carbon dioxide interacts with water so that the pH goes down.

Other things in the water can also alter any of these values. Some act on more than one thing, others are pretty specific.

If the water company adds sodium hydroxide to the water then the pH goes up, but not the GH or KH.

If you add limestone, coral sand, or related materials then GH, KH and pH generally go up.

Here is how I would handle this problem.
1) Find out the optimum GH for the fish. (Otos, low GH, say about 3-5 optimum, a bit higher OK).
Set the water at that with GH booster if needed.
2) Make the KH = GH within about 1 degree of hardness. So, if you set the GH at 4 degrees, the KH will be anywhere from 3-5 degrees.
3) If you are keeping black water fish then add some peat moss to add the organic acids these fish like.
4) Get the CO2 running at a low level and monitor GH, KH, pH, TDS. Monitor the CO2 with a drop checker. As long as GH, KH and TDS are stable, ignore the pH.
the pH could change a whole number and the fish do not mind- for example from 7.0 to 6.0 though a 24 hour cycle is just fine. The TDS, GH, KH need to be stable, and pretty close to the fishes' optimum values.
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