# PH swings during water changes?



## bdement (Jan 27, 2005)

I'm not really sure what the question was in your post, but...

In San Francisco the water out of the tap is 8.2 (and very soft), and the water in my tanks with CO2 injection is in the low 6's, very similar to your situation. I've noticed stress due to pH fluctuation in only 10-15 minutes when I forgot to add buffers. I have never had a problem with pH fluctuation when adding the correct buffers during water changes.


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## BradC (Dec 22, 2010)

Sorry as I reread my post I realized that I didnt really ask a specific question. What I was trying to ask is if the PH swing from a water change is dangerous to fish, etc. Esp with my water parameters. From your post I can see that it would prob cause stress. What kind of buffers are you using during your WC?


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## Hoppy (Dec 24, 2005)

I don't think you will find many experienced planted tank keepers who add buffers when they do a water change, nor even concern themselves with pH. Generally, from what I have seen and know, people just use pure tap water for water changes, adding some Prime or equivalent to take care of chloramine and chlorine, and enjoy watching the fish being so vigorous and alive immediately afterwards. When you do this you are very likely not changing the TDS, the KH or the GH any significant amount, and that is what would bother the fish. Clearly a few people have tap water that is so bad for various reasons that they use RO/DI water to avoid problems, but most don't do that.


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## plantbrain (Dec 15, 2003)

I've never seen any associated stress, only good health from large water changes, and the pH changes are typically 1 full unit of pH.

This has been occuring universally for the last 15 years in all my tanks.
And most others..........

CO2 is causing the decline in pH, Not less TDS/Salts, buffers etc.

CO2 is not a salt last I checked nor is it a buffer.

Blood systems are trying to unload CO2 efficiently in fish, so removing say 40ppm of CO2 in the water and adding only 5ppm is going to help, not harm fish in this respect.

Since CO2 is not a salt, this has little effect on osmoregulation.
pH differences does effect cell transpport, but that is an internal process, and shielded from the outside. Otherwise fish would be far far more sensitive to slight changes in pH and would die very easily.

Bottom line is do not worry about it.

There's a great deal of practical observation and evidence that suggest in a tank where CO2 is used, it does not matter directly.

Regards, 
Tom Barr


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## BradC (Dec 22, 2010)

Thanks Hoppy and Tom! 

I knew that the drop in pH from CO2 normally would not have any effect on fish. I was just worried about putting in water of a higher pH (more than 1 unit) and then shortly after (24-48 hours) it dropping back down again. 

Now I know that since CO2 is being injected that the drop in pH has no bad effect vs if I did not have CO2 and the pH dropped.

Thanks again,
Brad


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## Hoppy (Dec 24, 2005)

I have often wondered about the "stuff" that water companies add to the water to keep the pH above 7. I have read that they might use phosphates or lime, but I'm not at all sure, nor do I know what any individual water company uses. That leads to people having high pH with low KH in their tap water. I'm assuming the amounts involved are too small to affect the fish, but I admit that I wonder at times. Does anyone know more about this?


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## barbarossa4122 (Jan 16, 2010)

My pH goes down a bit after wc from 7 to 6.6. I use a little crashed coral inside the canister. I keep goldfish and did not notice any stress.


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## Diana (Jan 14, 2010)

My local water company adds sodium hydroxide to keep the pH up. I called and asked. 
GH and KH hover around 4-5 degrees through the year, but the pH can be anywhere from 7.6 to 9. 

Fish are more concerned with the mineral and salt levels in the water. If the new water has the same GH and KH and TDS as the old water it is not a problem that the pH changes. 
I have had problems moving fish from one tank to another when the mineral levels are different. This relates to the osmoregulation that fish must do to stay alive. The contact through the gills of tank water and fish fluids allows the exchange of more things than just oxygen and carbon dioxide. 

When there are more minerals in the water than in the fishes' tissues the fish loses some of its internal water to the tank. This raises the concentration of all the things in the fishes' cells and can kill the fish. The fishes' body compensates, and the levels maintain their optimum levels. This is the situation for fish in marine conditions. They have ways of keeping the water they need and getting rid of excess salts and minerals. 

When there are less minerals in the water than in the fishes' tissues the fish gains water from the tank. This drops the concentration of all the things in the fishes' cells and can kill the fish. The fishes' body compensates, and the levels maintain their optimum level. This is the situation for fresh water fish. They hold onto most of the minerals, and get rid of excess fluid. Fresh water varies, though, so simply saying it is fresh water is not enough. Fish moved from hard water to soft, or from soft water to hard can have problems. Many years ago fish keepers had no way to test mineral levels, just pH. Often as mineral levels in the water change the pH also changes, so these fish keepers thought they had a pH problem. It is not a pH problem. 

Problems happen when the mineral and salt level in the water changes too fast. If the levels change slowly the fish can adapt. Slow changes over several weeks (within the tolerance range of the species) are not a problem. 
Fast changes (such as buying a new fish, moving fish from one tank to another, or a large water change) create too large a change in the water chemistry for the fish to be able to adapt. 
Check the GH, KH, and TDS of the water the fish are adapted to, and test the new water you want the fish to be in. If these numbers are less than 10% different the fish will probably be fine. If the waters are too different you have several options:

1) Alter the water. 
This is what bdement is doing adding things to the very tap soft water when the tank water has fertilizers and other things in it. When the levels are similar, the fish are fine.

2) Put the fish in a quarantine tank.
Make the Q-tank water match where the fish came from, and slowly change the water (take a month to do this) Then put the fish in the main tank. This is what I do when I buy new fish.


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## Herbicidal (Aug 3, 2010)

I too am concerned with pH swings or perhaps more accurately in my case, pH dropping! I'm using a (new) digital pH tester, re-calibrated this past weekend to 7.0. Water from our tap is now 9.2, a few months ago it was 8.2. I "age" the water (overnight) before doing a water change in two 35-gal plastic trash cans, that of course, have only been used for this purpose. I'm only adding 3 tsp of Amquel per trash can, adding a larger airstone to each and a separate heater set to 84 degrees.

When I test the water the following day, it is typically @ 7.2 - 7.4. (also tested with a liquid test kit) Quite a drop with just airation! A non-airated glass of water sitting on the counter may drop to 8.9 after the same period of time.

My 155 gallon planted Discus tank has 3" of Eco-Complete substrate (started in August 2010), 3 medium sized pieces of driftwood, a Rena XP3 and an XP4 canister filters just cleaned both within the past week, 3 days apart. The XP3 contains only filter pads and some bio beads/stars. The XP4 contains all of that, plus some (fresh) charcoal to help remove the tannins from the water. NO CO2. Liquid ferts twice a week, started this regime about 2 weeks ago. I tested the pH on Thursday of last week in the tank and it was like 5.6, I don't recall the exact number but in the upper 5's. I was a bit concerned to say the least! I whipped up two cans of water (~60 gallons total) Friday night and did a water change Saturday morning. I don't remember the exact numbers but it prompted me to set up another 60 gallons of water and did another change later that day. I tested the pH in the tank on Sunday and it's 5.2!!! I'm at a loss as to why the pH is dropping like this! The fish and plants all look OK, but still it concerns me that the water is becoming too acidic.

Thoughts/suggestions? Should I add something to the canister filters to help bring the pH back into the mid 6's? Water changes don't seem to be helping much. *Thanks* for reading my long description, hopefully I have provided enough detail.

*PS:* after reading the other replies, I need to test for GH and KH. I don't believe I have a way to test TDS.


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## Hoppy (Dec 24, 2005)

Sometimes a weird test result just means the test is wrong. A drop to below pH 6 suggests to me a lot of CO2 in the water, but if you aren't adding CO2, I would suspect the test results first.


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## Herbicidal (Aug 3, 2010)

Hoppy said:


> Sometimes a weird test result just means the test is wrong. A drop to below pH 6 suggests to me a lot of CO2 in the water, but if you aren't adding CO2, I would suspect the test results first.


I've tested with the digital tester and a liquid based test kit, same results. That was why I recalibrated the digital tester. I've also checked my kids aquariums, no driftwood or plants and the pH is more what I would expect in a 7.2 range, plus or minus .1. So I'm confident that my tester is OK.

I've read where some folks have added some crushed coral to the gravel or into a canister filter. Might this help buffer the pH back up to the 6's? Thoughts on that approach? Should I continue with rather large water changes until the pH comes back up?

Thanks!


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## Hoppy (Dec 24, 2005)

If you believe that the tannins from your wood in the tank are causing the pH drop, you can add baking soda to the water to raise the KH. That will buffer the water better. If you already have water with a KH above 2 degrees or so, the only effect of the baking soda will be to raise the pH, not add more buffering. Is your tank water yellowish in color, from tannins? If not, I don't see how you could have enough tannins to give that effect, unless the tank water KH is below 1.0 degrees.


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## Captivate05 (Feb 23, 2010)

Hoppy said:


> I have often wondered about the "stuff" that water companies add to the water to keep the pH above 7. I have read that they might use phosphates or lime, but I'm not at all sure, nor do I know what any individual water company uses. That leads to people having high pH with low KH in their tap water. I'm assuming the amounts involved are too small to affect the fish, but I admit that I wonder at times. Does anyone know more about this?


From what I understand, some places use lime and soda ash to bring down the hardness in ground water. I guess it bonds with calcium and magnesium and solidifies it. At the same time, it raises the pH to a more alkaline level to prevent acidic erosion on the water pipes. It also makes the water taste nasty, IMO. :icon_conf


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## Herbicidal (Aug 3, 2010)

Hoppy said:


> If you believe that the tannins from your wood in the tank are causing the pH drop, you can add baking soda to the water to raise the KH. That will buffer the water better. If you already have water with a KH above 2 degrees or so, the only effect of the baking soda will be to raise the pH, not add more buffering. Is your tank water yellowish in color, from tannins? If not, I don't see how you could have enough tannins to give that effect, unless the tank water KH is below 1.0 degrees.


I don't think the driftwood is causing it. I soaked all the pieces for several weeks before putting them in the tank, sometimes using hot water and changing the water daily. They've been in the tank now for 4 months. The water just had a slight yellow tinge. Now it is clear and I'm only running charcoal in one canister filter.

I just tested the GH and KH and both give me approximate readings of 5 degrees or 89.5 ppm. Looking back over saved data, these numbers are consistent with tank startup back in August of last year.

Just to throw in a curve ball...I have a quarantine tank (20 gallons) with a H.O.B filter that contains the Rena black bio stars and a filter pad. Nothing else in the filter. In the tank: an air stone, no substrate, no driftwood, nada. I drained it completely this past weekend (Saturday) and filled it up with 20 gallons of "aged" water. pH: 7.2, temp 82 degrees. Nothing added other than some Amquel. Sunday we picked up some new fish from several different stores, soaked the bags, acclimated the fish in the bags with water from the tank, never putting bag water in the tank, always dumping it out. Checked the pH when I came home tonight: *4.3*!!!  I immediately filled one of my water changing trash cans from the tap, added Amquel an airstone and a heater. pH right after filling: 8.4 @ 78 degrees. Let it sit in the trash can for an hour and did a 5 gallon water change. Checked the pH in the QT about 30 minutes later and it had climbed up to 6.2. I pulled out all the bio stars and left just the filter pad. The bio stars had been in use for just over a month. Waited about an hour and changed out 5 more gallons. Just checked the pH and it is: 6.8 @ 78 degrees. I sure hope the change *up* in pH won't send them into shock.  I'll check the pH again in the morning when I get up which is @ 5:30am.

The Discus tank is at a pH of 5.4 @ 82 degrees as of tonight, still way lower then I would like. Both canister filters have bio beads and the bio stars. I'm real curious to see what happens to the pH on the QT.


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## Herbicidal (Aug 3, 2010)

The pH this morning in the QT is *6.6*, down slightly from last nights 6.8. I lost one Cory in the process.  Hopefully the pH swings won't create any more casualities. I'm really beginning to suspect the bio stars. Other than a new filter pad (no charcoal in the pad) that was the only other thing that I changed for the QT. Tonight, I will remove the bio stars from both of my canister filters on the Discus tank and do another water change in the next couple of days to see if I can 'pull' the pH up out of the 5's.


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## plantbrain (Dec 15, 2003)

My tanks do a full pH unit in a few minutes, never lost a fish due to this EVER.

Regards, 
Tom Barr


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## plantbrain (Dec 15, 2003)

Bring a pH meter or borrow mine on my water change day and see for yourself.

Sort of falsifies any of this pH swing monkey business quackery I've heard for the last 20 years worth of myths in this hobby.

After keeping numerous tanks and over decades, you sort can say with fll 100% confidence what is *not* killing the fish here.


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## Herbicidal (Aug 3, 2010)

Last night I checked the QT again and it dropped into the 5's. So apparently the bio stars are NOT the culprite. This morning it was at 4.1. Just water, an air stone, heater, H.O.B filter with only a filter pad in it, plus about a half dozen small fish. The water I'm adding to QT is aged water sitting for two days now at a pH of 7.2 (heater and airstone running as well).

Tonight, I need to check all the water parameters that I can: Ammonia, nitrites, nitrates, GH, KH and phosphates. I just don't understand why the bottom is falling out on the pH side, ESPECIALLY since my source water is aged and is stable at 7.2.

Tom - with my QT's pH in the 4's, the water is getting quite acidic. From the research I've done on pH, the pH scale is logarithmic, so each step up or down is 10 times that of the previous one. As the article shows in my link below, a pH of 6 is *ten times* more acidic than a pH of 7. A pH of 5 is *100 times* more acidic than a pH of 7! (http://www.freshwater-aquarium-fish.com/index.php?option=com_content&task=view&id=26&Itemid=1). Here's a direct quote from within that link regarding pH and fish "_It affects their breathing ability. High acidity or alkalinity can cause direct physical damage to skin, gills and eyes. Prolonged exposure to sub-lethal pH levels can cause stress, increase mucus production and encourage epithelial hyperplasia (thickening of the skin or gill epithelia) with sometimes-fatal consequences._"

With all due respect, I understand swings of plus or minus 1 point may not kill your fish, but it will be causing them some stress. If they are healthy, as yours obviously are, then they are able to take the pH swings in stride.

Also tonight, I need to get those fish out of QT and slowly acclimate them to their final destination tanks before I kill any more. Then tear down the quarantine tank and do some 'fish-less' pH experimentations on it after it's refilled.


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## Herbicidal (Aug 3, 2010)

*UPDATE:* back on Wednesday of last week, I pulled all the fish out of quarantine and slowly acclimated them to their new homes. Everyone as of today is doing fine. I completely drained the QT and at the moment it remains dry. I did two water changes (total of ~ 120 gallons) on my 155 over the weekend using "aged" water with a pH of 7.2. On Sunday morning, the pH was only 5.8. I went out to a LFS and bought 4 lbs of medium size crushed coral, not the sand. I shut down my XP4, pulled the charcoal out of one of the baskets and added aprox. 2 lbs of the crushed coral (rinsed) between two filter pads. This morning before leaving for work, I checked the pH and it's now up to 6.7. So over the course of about 14 hours, the crushed coral pulled up the pH almost one full point. I'll check it again tonight to see if it's climbed any higher. If it has, I'll probably pull out about a pound and see what happens. I'll do daily pH checks probably for a week to ensure it's not bouncing. I'm cautiously optimistic that I may have it figured out AND I'm not using chemicals to alter the pH. Crushed coral is cheap and easy to replace. Honestly, with my tap water pH coming out in the mid 8's or higher, I NEVER thought I would have a low pH problem. Live and learn.


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## Hoppy (Dec 24, 2005)

I can't think of any way water can drop into the pH 4 area unless you are adding an acidic substance. CO2 won't drop it that far. I doubt that tannins from "driftwood" can drop it that far. But, not being a chemist, I can't imagine what acidic substance you could be accidentally introducing. I wish one of our chemist members would offer some suggestions.

It is always tempting when faced with an apparently impossible test reading to say that there is something wrong with the test method.


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## Herbicidal (Aug 3, 2010)

Believe me Hoppy, I've been banging my head on that one! There are two different scenarios I have been describing. I apologize if I intertwined them and caused some confusion. The first was the *20 gal. QT* and the second is the *155 gallon Discus tank*. I confirmed my pH findings with both the digital pH test meter and my API liquid pH tests. I had also recalibrated the digital tester with the supplied calibration fluid to 7.0 just to make sure I wasn't losing my mind! Testing pH is pretty darn straight forward, either digitally or chemically.

It was only the *20 gallon QT* that dropped into the 4's. Bare bottom tank, H.O.B filter, with only a filter pad, airstone and heater. Fresh water going into it was a pH of ~ 7.2. Within 24 hours, it was back into the 4's.

My *155 planted Discus tank* dropped to a low of 5.4. Through 120 gallons worth of water changes over the weekend, it came back up to 5.8. Not really much of a change and I just can't continue on that water changing pace. Which led me to adding the crushed coral to the canister filter yesterday. As mentioned previously, this appears to be working. Now I have to make sure I don't go too far the other way!


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## Hoppy (Dec 24, 2005)

One thing that would result in low pH is a KH below 1 degree, say 5 ppm, for example. That could allow the pH to change drastically with just small changes in tannins in the water. I notice your GH and KH are the same 5 degrees, which isn't the usual case. Perhaps your KH test kit is a mislabeled GH test? Or the KH kit is simply way off? Why not spend some time playing with that test kit to make sure you trust it?


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## Herbicidal (Aug 3, 2010)

Perhaps we've found a topic for our next S.A.P.S meeting! Water testing: how to do it correctly, what it means, calibrating, reliability and what should you do if something has run amuck! Just a thought... :icon_wink


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## Hoppy (Dec 24, 2005)

Herbicidal said:


> Perhaps we've found a topic for our next S.A.P.S meeting! Water testing: how to do it correctly, what it means, calibrating, reliability and what should you do if something has run amuck! Just a thought... :icon_wink


Sounds good to me. Why not email the SAPS group to see what others think?


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## Herbicidal (Aug 3, 2010)

Hoppy said:


> Sounds good to me. Why not email the SAPS group to see what others think?


Done. roud:


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## Loligo (Jan 25, 2011)

How have the tanks been doing? Anymore insight into what was causing the low pH?


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## Herbicidal (Aug 3, 2010)

Loligo said:


> How have the tanks been doing? Anymore insight into what was causing the low pH?


Hi Loligo - since adding the crushed coral to the basket in the XP4 and even adding a small amount to the HOB filter on the 20 QT, the pH has stabilized at 7.3 on my 155 and 7.1 on the 20. I've removed about 1/2 of the crushed coral from the XP4 since I started using it. So far, so good. Still no idea as to why it was plummeting like that. Continuing to monitor, but more on an every other day basis.


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## Hoppy (Dec 24, 2005)

Since crushed coral seems to have corrected the problem, that convinces me that you had very low KH, like 5-10 ppm, and that made the pH be unstable. Now the KH is up high enough, over 1 degree KH, for the pH to be stable. If this is what happened, it is the first time I have ever seen a report on this phenomena that was credible.


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## Herbicidal (Aug 3, 2010)

I checked the gh and kh during that time period and according to my test kit, they were both (tank and tap) in the 5 degrees or ~ 89 ppm range. Perhaps today I will pick up another test kit and check both the tap and tank water again. The liquid test bottles I used where purchased new in August of last year, so about 5 months old? Of course I don't know how long they sat on the shelf before I bought them. I also did some searching on the internet and found a report of the water for my area. The report was from 2009. Here's a link and the relavant info is on the last two pages if you're interested: http://www.amwater.com/files/CA_3110150_CCR.pdf. I'm in the City of Roseville, and I think getting water from the Diamond Creek Well. I will try to check with the city today and see if I can obtain a more current water report to bounce my test results off of.


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## Loligo (Jan 25, 2011)

Interesting... I'm glad the crushed coral stabilized things!


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