# pH keeps dropping



## aQualung (Oct 20, 2010)

I have a 27 gallon acrylic hex tank set up with 1 harlequin rasbora and one Juli cat in it. The tank has been set up 5 or 6 weeks now. It has 2 Amazon swords and 1 fast growing wisteria. It also has a gravel substrate and a piece of driftwood that is moderately sized relative to the tank. I also have soft water.

If I go more than 2 or 3 days between water changes the pH seems to drop to 6.0 (maybe even lower if my testing kit went lower).

Is this a potential problem with the tank? What would cause this to happen? Another concern is that my girlfriend and I will be going on a ski trip for 4 days and would hate for the pH to drop too far while we are gone.

We had a tank emergency about 3 and a half weeks ago now that wiped out 6 of our nine fish and another died almost 2 weeks ago now. We couldn't figure out the cause of this as our Ammonia, NitrIte, and NitrAte tests were all at 0.

I would love to put some more fish in the tank in a couple of weeks but need to make sure the tank is safe.


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## chris oe (Feb 27, 2009)

I'm thinking you probably have a low carbonate hardness causing this, and increasing it would help stabilize your ph. Have you got a carbonate hardness test? You could just go straight to adding some dolomite (its the grey gravel people put in their gravel driveways) or some clam or oyster shells in. You can hide them in the tank or even put the gravel or the shells into your filter. Make sure they're very very clean. (I like to boil shells just in case, particularly since if I get something from a restaurant I don't want any meat still on it. You can break them up so they don't impede water flow in your filter if that's how you do it.) Let us know how this works for you.


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## Gizmo (Dec 6, 2010)

As stated above, carbonate hardness (KH) and pH have a direct relationship, and this is dependent on the CO2 concentration in your tank. KH is a pH "buffer", so to speak, because a higher KH will prevent pH swings due to dropping and rising CO2 concentrations.

Your plants consume CO2 and produce O2 in the daytime, and at night they do the opposite. This results in a gradual shift in pH throughout the day as CO2 concentrations that have built up in the tank overnight are depleted by photosynthesis. The lower your KH, the more drastic the pH swing will be.

There are methods to boosting KH, some of which I remember vaguely (like a bag of crushed coral substrate), which will solve your pH problems. DO NOT USE PHOSPHATE pH BUFFERS! They are harmful to plants, and do not fix the problem.

Hope this helps!

Note: Fish can tolerate a wide range of pH's, so long as they stay constant. Once you boost your KH, your pH should even out. After that, leave it alone.


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## rtbob (Jul 18, 2010)

Do you have a water softener system hooked into your plumbing? The kind you have to dump those big bags of salt into?


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## Gizmo (Dec 6, 2010)

I actually have one of those, and the KH and GH out of the tap are still 8 and 9 degrees, respectively. Wouldn't want to know what they are coming in directly off the city's line.


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## jrman83 (Jul 9, 2010)

Definitely need to get a gh/kh test kit to see what the alkalinity is in the water. 

What does your ph start out as if it drops to 6.0? A mild swing (.2-.3) could be caused by the driftwood. I see a .2 drop from mine.


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## Amie (Sep 15, 2010)

I would suggest taking out the driftwood first as the easiest solution to the problem. Also, unless it is a big swing then the fish won't mind.


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## chris oe (Feb 27, 2009)

You should think about finding a way to get unsoftened water for your tank, I suspect water softener water will continue to cause you problems.


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## snail (Aug 6, 2010)

aQualung said:


> I have a 27 gallon acrylic hex tank set up with 1 harlequin rasbora and one Juli cat in it. The tank has been set up 5 or 6 weeks now. ...
> We had a tank emergency about 3 and a half weeks ago now that wiped out 6 of our nine fish and another died almost 2 weeks ago now. We couldn't figure out the cause of this as our Ammonia, NitrIte, and NitrAte tests were all at 0.


That sounds like perfect timing for an ammonia spike to me. Could your tests be wrong?


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## Gizmo (Dec 6, 2010)

aQualung said:


> We had a tank emergency about 3 and a half weeks ago now that wiped out 6 of our nine fish and another died almost 2 weeks ago now. We couldn't figure out the cause of this as our Ammonia, NitrIte, and NitrAte tests were all at 0.


I always get leery when people report zeroes across the board on the nitrogen cycle. My first thought when you did this is that you might have cleaned the tank a little too well during a PWC and had to restart the cycle, then lost your fish to an ammonia spike.

It could also have been asphyxiation. If your pH dropped really low at the time, it means your tank was flooded with CO2. And without a good source of oxygen in there, you might have suffocated your fish. Asphyxiation is a silent killer and it's very hard to see when it will strike, and there are several possible causes.

Questions to determine if it was asphyxiation:
1. Do you inject CO2? And if so, do you turn it off at night?
2. How much dechlorinator and/or medication was in the tank at the time?
3. Do you have some sort of surface agitation like a bubbler or an HOB filter, to allow gassing-out?

Hopefully we can track this mystery problem down *epic mystery thriller music*


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## chris oe (Feb 27, 2009)

Fast growing plants like Wisteria can do the same thing, since during the night they metabolize the food they've been creating by photosynthesis during the day, causing them to consume o2 and produce co2, so a large mass of fast growing plants with an abundance of nitrate at their disposal can cause asphyxiation as well.


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## aQualung (Oct 20, 2010)

rtbob said:


> Do you have a water softener system hooked into your plumbing? The kind you have to dump those big bags of salt into?


No we have straight city water into the building.


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## aQualung (Oct 20, 2010)

snail said:


> That sounds like perfect timing for an ammonia spike to me. Could your tests be wrong?


I doubt it. I've been using the API master kit for all my tests and follow the directions. We used to read at 0ppm Ammonia, 0ppm NitrIte, and 20 ppm NitrAte at it's highest. Then the plants started eating up all available nitrate.

We haven't had a number above 0 for about 4 weeks now.


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## aQualung (Oct 20, 2010)

[email protected] said:


> I always get leery when people report zeroes across the board on the nitrogen cycle. My first thought when you did this is that you might have cleaned the tank a little too well during a PWC and had to restart the cycle, then lost your fish to an ammonia spike.
> 
> It could also have been asphyxiation. If your pH dropped really low at the time, it means your tank was flooded with CO2. And without a good source of oxygen in there, you might have suffocated your fish. Asphyxiation is a silent killer and it's very hard to see when it will strike, and there are several possible causes.
> 
> ...


I am pretty confident in the testing results. 

If plants really do produce CO2 at night then maybe that's it as it was combined with a DIY CO2 hookup. I did turn it off at night though.

I've had an HOB since day 1 though so I assumed that would help with gassing out the tank. Although at the time with 9 fish in there maybe it was a little too much for the HOB to handle? This may have caused a jump in CO2 concentration.

Last time we used dechlorinator before the tank went downhill was a Friday night. Monday morning is when this stuff happened.


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## aQualung (Oct 20, 2010)

chris oe said:


> Fast growing plants like Wisteria can do the same thing, since during the night they metabolize the food they've been creating by photosynthesis during the day, causing them to consume o2 and produce co2, so a large mass of fast growing plants with an abundance of nitrate at their disposal can cause asphyxiation as well.


This explanation makes some sense as to what might have happened.

What could prevent this? Get rid of the wisteria? I was under the assumption that plants would help oxygenate the water and not do the opposite.


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## aQualung (Oct 20, 2010)

jrman83 said:


> Definitely need to get a gh/kh test kit to see what the alkalinity is in the water.
> 
> What does your ph start out as if it drops to 6.0? A mild swing (.2-.3) could be caused by the driftwood. I see a .2 drop from mine.


My treated tap water is around 7

I doubt the driftwood alone would cause that unless my water really is that soft. I have tested the gh and kh in the past month and it was really really low.


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## jrman83 (Jul 9, 2010)

What?????????? You never said you added CO2!!!!! CO2 will lower your ph. Enough said.


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## aQualung (Oct 20, 2010)

Thanks for the help everybody!


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## aQualung (Oct 20, 2010)

jrman83 said:


> What?????????? You never said you added CO2!!!!! CO2 will lower your ph. Enough said.


Oh sorry should have clarified... I haven't hooked it up for over a month

Maybe 5 weeks and the pH still drops


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## Gizmo (Dec 6, 2010)

aQualung said:


> Maybe 5 weeks and the pH still drops


So you're saying you haven't had your CO2 running for 5 weeks and your pH is still low? And you use an HOB filter? So it seems CO2 is not the cause of your most recent pH readings, but it explains previous stuff, and might have given rise to the deaths of your fish. And the fact that you have extremely soft water also gives away such low pH readings - with fast-growing plants like wisteria and very soft water, your pH will bottom out, CO2 or no. And with possible interference with driftwood, I think the case is closed on why your pH is low.

Solution: No need to get rid of your wisteria, just find a way to boost your hardness and alkalinity. My favorite is Grumpy's GH booster, at Rex Grigg's website found below:

Fertilizers For The Planted Tank | Ferts

How exactly did/do you turn off your DIY CO2 at night? I wasn't aware there was a way to turn off DIY systems short of decommissioning it for the night by removing the yeast fermentation bottle. How are you introducing it into the tank? Diffuser? Reactor?

Another thing that might have gone wrong - if you mix the wrong ratios of sugar yeast and water, the yeast will flood into your tank and that would REALLY ruin things for your fish and your entire system. Be careful when working with DIY CO2, always use a recipe that's been proved tried and true.


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## jrman83 (Jul 9, 2010)

DIY CO2 can be made useless at night fairly easily. My DIY tank turns on a bubbler when the light goes out. My diffuser is also powered and it shuts down too leaving just big glob bubbles that go straight to the surface. Bubblers will gas out the CO2 in your tank from the surface disturbance.


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## chris oe (Feb 27, 2009)

Thanks for the link to the planted tank guide - excellent stuff on there. I'd been looking for a good, cheap source of calcium to dose my tank with. Been tempted to buy a bottle of kalkwasser (spelling?) this looks better.


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## aQualung (Oct 20, 2010)

[email protected] said:


> So you're saying you haven't had your CO2 running for 5 weeks and your pH is still low? And you use an HOB filter? So it seems CO2 is not the cause of your most recent pH readings, but it explains previous stuff, and might have given rise to the deaths of your fish. And the fact that you have extremely soft water also gives away such low pH readings - with fast-growing plants like wisteria and very soft water, your pH will bottom out, CO2 or no. And with possible interference with driftwood, I think the case is closed on why your pH is low.
> 
> Solution: No need to get rid of your wisteria, just find a way to boost your hardness and alkalinity. My favorite is Grumpy's GH booster, at Rex Grigg's website found below:
> 
> ...


My gut is telling me you are right about the CO2 going crazy one night combined with the DIY. With 9 fish in the tank they probably helped suck up so much O2 as well. Now with only 2 we haven't had any issues at all since. Maybe I will only stock a couple more fish and not jump back up to 9... especially so quick.

As far as turning it off I would just unscrew the cap and let the CO2 bubble into the atmosphere. The recipe I used was a pretty standard one and I know it wasn't dumping into the tank.

I used a diffuser for my bubbles.

Thanks for the point out to that site I will definitely pick some up after I get back from my ski trip.

Thanks a lot!


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