Water Change = Big Ph Swing

[Sysiphus]

Originally posted under emergencies but moderator suggested I move here for more viewing

Hard to know where to start this tale - so here is the basic tank setup:

Setup on 11/4/06, 90 gal, 78 degrees, Corallife 65 watt 4 light 6K range on 10 hours a day 2.8 watts /gal, Pressurized C02 on pH Auto-Regulator 7.0 25 ppm C02, Rio reactor, 11 degrees hardness, 120 ppm Alkalinity, Fluval 405 Canister...

Balansae, Wendtii “Redâ€, Dwarf Subulata, Tall Subulata, Corkscrew Val, Anubias Petite, Anubias Barteri, Hairgrass, Java Moss, Wisteria, Lobelia small form...

2 - 4" upside down cats, 5 - 3" glass cats, 1 - chocolate Pleco, 1 - L146 Rubber Pleco, 2 - 4" Silver Dollars YIKES, 2 - Rummy Nose Tetra, 8 Neons...

Run 2 airstones at night don’t cut off C02 and 8 LED light blue night light.

****************** Here is what is happening

No significant problems except for the last two months. I change 15% water 2X’s a week. Change water is both aged (3-4 days) and declor treated. Here is the problem:

Within 5-7 hours after a water change the pH begins to drop from 7.0 until it gets to about 6.5 - water goes cloudy and fish all show stress signs. Took a reading of water chem during the problem time and it is:

pH 6.5 <<<
Alkalinity 40 <<<
Hardness 50
NitrIte 0
NitrAte 40

Took a reading of my change water (after it has sat for 3 days and been declor treated):

pH 6.8
Alkalinity 130
Hardness 0 <<<<
NitrIte 0
NitrAte 0

Just as a base - water test right from the tap (cholorine can sometimes mess with the results but I think these are on the mark):

pH 7.3
Alkalinity 130
Hardness 0
NitrIte 0
NitrAte 0

My plan is to increase alkalinity by adding crushed coral to the filter media. This should also bring up the hardness?

I did not mention but the water stabilizes at pH 7.0 after about 48 hours and water returns to perfectly clear. What I am assuming is that over time since the setup, the C02 has eaten all the buffering ability out of the water which accounts for good tank/bad tank syndrom I now experience.

As a stop gap to my runaway pH I am using Seachem PH 7.0 Liquid Neutral Regulator and that does bring the pH up but during the first 48 hours the pH bounces.

STATUS TODAY (3 days after above post)

So here is where I am today… I have a working theory helped along by a LFS that I feel generally good about (not a “big box†fish shop).

Here is the working theory:

After 4-5 months of C02 introduction and with soft water going into tank the alkaline buffer has been complete exhausted. I am not sure I buy into this next part but I have nothing better – the LFS suggests that detritus are not decomposing well in the soft water and by using a product called “Liquid Gravel Vac†I can kick that into gear. The poor decomposition creates an acidic condition according to the LFS and when I do my water changes I “kick that up†and the pH is adversely affected. So keeping my personal need to only make modest changes in the tank, I have introduced two fist sized tufa rocks that should add some hardness to the water and a dose of the “Gravel Vac†(made by Tropical Science Labs in Phoenix, Arizona).

So I am taking Gravel Vac on faith and trying to address the one test result I believe I must correct by improving the low alkaline base.

The pH has been a steady 6.9 for 3 days and I have not yet taken alkaline readings since I just introduced the tufa rocks 10 hours ago. At this time tank conditions seem excellent. Next water change on Sunday will tell a big tale.

You can see the original post under fish emergencies "Water Dunderhead"

 

[rdd1952]

I posted on the other thread but will put it here too. Be careful of the Liquid Gravel Vac. I'm almost of the opinion that it will have the opposite effect that the LFS suggested. There are bacteria present in the tank that break down dead leaves, excess food, etc. In doing that, they consume oxygen. If that produce kicks them into overdrive and they consume excess oxygen, thus lowering the oxygen content and raising the CO2 content of the water, it could actually drive the pH lower as oxygen,CO2 and pH are all directly related.

 

[Dave Spencer]

The buffering capacity of your water is around 7dKH, which is plenty, and will not be exhausted by your CO2. My water is 3dKH and I have my CO2 at 30ppm. Every time you do a water change you are replenishing the buffering capacity. I suspect your LFS is talking crap. The effects of O2 on pH are negligible, particularly when regarding the effect CO2 has.

Apologies, but I am struggling to get my head around why you are worried about a pH swing of 6.5 to 7 in your tank. My tank runs at a pH of 6 during the day, and changes by .4 every night when the CO2 is off, and by even more during my weekly 50% water change (I very rarely test my water). Are your fish stressed, because I have Amano Shrimp and Otos that take this in their stride?

Your pH changes are relatively small and over a decent period of time. Personally, I would be happy with the water, and under no circumstances would I be adding anything specific to alter the pH.

I am not sure what is causing the cloudiness and stressing your fish. Maybe you are disturbing the susbstrate during water changes.

 

[andywg]

oxygen,CO2 and pH are all directly related.

The dissolved levels of O2 and CO2 are completely independent. Just because you add CO2 does not mean the O2 goes down. I also doubt that bacteria breaking down detritus would have a massive effect on the O2 levels, certainly not compared to a fish.

With regarding the OP's lfs's theory, I wouldn't trust them at all. Your own results show that your water is plenty hard enough to buffer itself. If that liquid gravel vac really makes the stuff on the bottom decompose much quicker then you are going to see the pH fall. The end result of decomposition is an acidic compound. Having a huge increase in the rate of decomposing will not help your tank stay stable.

I believe your methods of buffering the water will do you far more good than the product your lfs has sold you which claims to contain non pathogenic bacteria to eat down the sludge. I can't figure out how they keep said bacteria alive in the bottle. Does it come refrigerated?

 

[Sysiphus]

I appreciate all the considerable thought in your replies. Current readings after 72 hrs of the tufa rocks being in the tanks:

pH 6.9
Alkalinity 90
Hardness120
NitrIte 0
NitrAte 70

Going to do a water change since NitrAte is a bit high - but I am pretty happy with this reading.

The C02 is 30ppm and that is higher than I ever have it. At 2 bubbles per second 20ppm has been normal for 5 months - I think this lends a good deal of support to the idea the gravel vac will increase C02.

This water change will be an interesting test that should tell if my problems have been caused from a lack of water hardness and fluctuating Alkalinity. My water change (water out) takes only minutes, but the refill (while automatic) is slow because it "trickels" in through an airtube line. So in about two hours after all replacement water is in, I will take another "after change" reading. One interesting thing I have already noticed after about 3 gallons have gone back in, is the pH has increased to 7.0! I don't think that has ever happend in the last two months of my observations. I noticed the increase because the C02 cut on, which also does not happen (recently) during water replacement.

I am TERRIBLE at taking pictures of my tank but throught I would post one so you know what you are working on!

The idea was to start adding in some more rummynose and plecos after the tank had run-in for about 4 months, but this problem has truly set me back.

 

[Sysiphus]

Reading after water change & Fert dose

pH 6.9
Alkalinity 90
Hardness 100
NitrIte 0
NitrAte 40



Now in about 3 hours will know if the pH swing will occur

 

[Dave Spencer]

If you are using a pH controller alongside your CO2, then your pH is going to drop, surely. Your tap water will contain less CO2 than your tank water, so the controller will allow the CO2 to build back up, lowering your pH.

I honestly think you have nothing to worry about and will only cause harm by trying to alter your pH. A pH of 6.5 is fine.

Dave.

 

[Jozlyn]

Just want to ask how you test for alkalinity, I've never seen a test for that?

 

[Dave Spencer]

Just want to ask how you test for alkalinity, I've never seen a test for that?

I would say he is referring to the carbonate hardness when he mentions alkalinity.

 

[Jozlyn]

Just want to ask how you test for alkalinity, I've never seen a test for that?

I would say he is referring to the carbonate hardness when he mentions alkalinity.

That would explaing how I've never seen a test then!

 

[rdd1952]

You mentioned that the pH of the water you had standing with the ferts in it waiting for a water change had a lower pH than the tap water. There is no reason the pH should change on it's own, especially since you are keeping it in a sealed container. I ran a bucket of water and let it sit for 2 and a half days and then tested pH again. There was no change in the pH from when it came from the tap. I strongly suspect the ferts you are using are causing the pH swing and cloudyness you are seeing.

I know you are letting the water sit to get to room temperature. If it were me, I would just use water from the tap and add a little warm water to get it to the proper temperature. I strongly suspect a large majority of members here do that rather than letting water sit.

 

[Sysiphus]

SUCCESS!

Rock solid pH of 6.9 and no cloudyness or fish stress.

The only change was the addition of tufa rocks which improved the water hardness from zero to 100 ppm and also had the effect of altering the Total Alkalinity/Buffering Capacity (which is a calcium and magnesium measurement) to 90 ppm. I kept to my regular fertilizer dose and did the water change as always.

Yes, I do think puting the ferts in the holding water was part of the problem. I also ran a bit of a test of my own on - I often (due to the strong influlence of my male sloppy gene) leave one of the holding tanks sit out without putting it back in the dark closet right away after a water change. In only the tank with ferts, in a bright room, left out all day, the pH begins to fall. I bet if I left it out a couple of days algae would begin to grow?

My aversion to using hot tap water is left over from a salt water problem I had where I put copper in the tanks by running hot water mixes. It caused me some serious problems; plus I have my current system setup so the tank will refill from the stored water unattended. Water removal & vac takes maybe 15 minutes, thats all.

I can't even begin to say what a relief it is to see this situation come into control. No doubt some peculiarities in my water change process combined with a varying buffering capacity and nil water hardness created this situation.

 

[Sysiphus]

If you are using a pH controller alongside your CO2, then your pH is going to drop, surely. Your tap water will contain less CO2 than your tank water, so the controller will allow the CO2 to build back up, lowering your pH.

I honestly think you have nothing to worry about and will only cause harm by trying to alter your pH. A pH of 6.5 is fine.

Dave.

Ur right of course - and if it had not been for the haze and notable fish stress I would not have been so reactive. pH change was I think just part of the symptoms and the soft water was the primary "big" problem.

 

[rdd1952]

I'm glad you got it figured out. One thing on the hot water and copper though. If your home has copper pipes for hot water, isn't it likely the cold water pipes are too (not a plumber so I don't have a clue)?

 

[Sysiphus]

I'm glad you got it figured out. One thing on the hot water and copper though. If your home has copper pipes for hot water, isn't it likely the cold water pipes are too (not a plumber so I don't have a clue)?

It is and they are, but I have tested and done some reading and transmission of hot water (especially with soft water) frees up considerably more copper than cold. I have not tested, but maybe the declor products that remove "heavy metals" take out copper as well? *sigh* looks like more reading is afoot. My copper "problems" were in a house in Georgia and I did test and found the hot water tap produced as hight as 2 ppm while the cold water tap did not register on a test kit that was sensitive down to .25 ppm. Both the softness of the water and probably uncoated pipes in that older house contrubuted greatly to the problems. Charcole does remove copper pretty effectively. Here in Arizona, I have not checked for copper and now I think I will. This is (afterall) the great copper mining state. Our local water system says there is less than .005 ppm in the municipal system.

I have heard more than one story around here of a pretty rock found for the aquairum, that contained lots of copper.