Ph Swings, waterchanges etc!

Hi Everyone,

Over the last couple of days I have been reading up on PH swings and I need another opinion and advice.

My water in the aging barrel has no PH swing, after 24 hours of heavy aeration and heating. The water comes directly from the tap, through a series of sediment/carbon filters and then into the barrel. The ph of this water is around 8.2-8.4. I should mention that there is about 0.25 Ammonia in the tap water, and is always treated with prime.

I have been watching my tank's PH, that swings from about 7.5 at night (lights dimmed or off) and climbs to about 8.0 during the day (lights on). I'm not sure what has changed but I don't recall the swing being this big in the past. I noticed my fish breathing heavy and a little bit stressed , so I started investigating. Currently I am doing 50% WC's daily, and have since day one.
I'd like to continue the large water changes, however my thinking is that I will have to be strict in that I will have to do it during the day when the aging barrel PH and tank PH is closer.

My other concern is the swing over night (as mentioned above), is this too large? Would removing plants be necessary in order to stabilize the PH or minimize the swing?

Any insight would be great,

Thanks,

Brendan

With plants are you running co2 at all, and have you tried aging your water longer maybe 48hr to see if you get a swing

Jeanne

Yeah that’s the plan with the current batch of water in the barrel. Nah no co2

Brendan have you checked you kH at all! The nitrogen cycle is an acidifying process, so if your kH is low or 0 the pH drop you are seeing could be related to your carbonates being consumed or depleted through the day and into the night resulting in the pH drop. If low/no kH is the problem you can add a bad of crushed coral or aragonite into your filter to mitigate the problem.
On another note, I am flying into Brissy in March to spend a week my folks on Nth Straddie. Can't wait!

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Originally Posted by danotaylor

Brendan have you checked you kH at all! The nitrogen cycle is an acidifying process, so if your kH is low or 0 the pH drop you are seeing could be related to your carbonates being consumed or depleted through the day and into the night resulting in the pH drop. If low/no kH is the problem you can add a bad of crushed coral or aragonite into your filter to mitigate the problem.
On another note, I am flying into Brissy in March to spend a week my folks on Nth Straddie. Can't wait!

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His PH increases with lights off though. At the beginning, mine had the opposite effect. It would decrease at night and increase during the day. However, there was only a .1 - .2 difference.

Mando I see your point, the pH swing is in the wrong direction for the acidifying process. Jeanne's suggestion then is what would test also, a 48 hours aging. Not sure why the pH change would take longer, but def worth checking.
Either way, kH still has a direct connection to pH stability so I would test that as welt...

My read is that the Ph drops to ~ 7.5 in the dark and comes up during the day to ~8.0. Or is that only due to the daily water change? How much of a plant burden do you have in the tank? As well, how much agitation to break the surface tension? Surface area vs volume? If you have a high tank which I have, consider aggressive aeration overnight when plants and fish are both competing for O2 and producing CO2 which, since it is reversible next AM, I would blame for the Ph drop rather than the production of nitrates and nitric acid. Regardless, the lower your Carbonate hardness the wider the ph swings so I agree, test and fix.

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Originally Posted by danotaylor

Mando I see your point, the pH swing is in the wrong direction for the acidifying process. Jeanne's suggestion then is what would test also, a 48 hours aging. Not sure why the pH change would take longer, but def worth checking.
Either way, kH still has a direct connection to pH stability so I would test that as welt...

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I read it wrong anyways! it does drop.

Quote:

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Originally Posted by danotaylor

Brendan have you checked you kH at all! The nitrogen cycle is an acidifying process, so if your kH is low or 0 the pH drop you are seeing could be related to your carbonates being consumed or depleted through the day and into the night resulting in the pH drop. If low/no kH is the problem you can add a bad of crushed coral or aragonite into your filter to mitigate the problem.
On another note, I am flying into Brissy in March to spend a week my folks on Nth Straddie. Can't wait!

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Hey mate yeah KH is 5-6. I was reading that ph will drop at night because the plants are no longer consuming the co2, and it rises during the day because the plants are removing the co2 from the water. I do have crushed coral on me that I can try. Just wanted to pick some brains first before I go doing anything.

Yeah mate if you’re around I’ve got cold beer in the fridge and we can talk discus!

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Originally Posted by dspeers

My read is that the Ph drops to ~ 7.5 in the dark and comes up during the day to ~8.0. Or is that only due to the daily water change? How much of a plant burden do you have in the tank? As well, how much agitation to break the surface tension? Surface area vs volume? If you have a high tank which I have, consider aggressive aeration overnight when plants and fish are both competing for O2 and producing CO2 which, since it is reversible next AM, I would blame for the Ph drop rather than the production of nitrates and nitric acid. Regardless, the lower your Carbonate hardness the wider the ph swings so I agree, test and fix.

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Tank is 6ftx2x2, two fx6’s outlets for surface agitation, and 3 air stones throughout the tank, running 24/7.

I’ll check the PH in the aging barrel this afternoon to see if it’s shifted after 48 hours.
I’ll also put a fist sized bag of crushed coral in one of the filters and report back with my findings. Sound ok?

Results this afternoon (3pm):

Ph -
Aging barrel (aged 48 hours) 8.5

Water straight from filter that fills aging barrel 7.5

Straight tap water, no filtering or aging etc 8.0

Fish tank 7.9

No crushed coral has been added yet, will do shortly

maybe some rock, sand make ph up. How long aquarium is started?

Kh is actually reasonable, you can bring it up to ~8 if you want but you already have adequate buffer. Hope you have a ton of plants, otherwise I am at a loss. Plants in the dark not only do not absorb CO2, they produce it, and in addition compete with the fish for O2, which sort of would explain the heavy breathing you observe (I assume first thing in the AM). But with your 3 airstones going would not expect your fish to be symptomatically hypoxic due to plants which they act like they are. Despite your 3 air stones you may actually have to increase aeration when dark, or reduce plants. My plan is to put bubble curtain walls along both sides of the my tanks to run at night to minimize this potential problem as I love planted tanks, but I have high tanks. You are always going to have some variance of ph, but I am surprised it reaches 0.5 as CO2 dissipates rapidly from liquid into atmosphere. How tightly sealed is your tank top? What kind of filter do you run that would drop your tap ph from 8 to 7.5? That it goes up to 8.5 is due to offgassing CO2. Also just to be clear, your ph recovers in the morning before your water change, or is it the water change that raises the ph from the night before?

Quote:

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Originally Posted by dspeers

Kh is actually reasonable, you can bring it up to ~8 if you want but you already have adequate buffer. Hope you have a ton of plants, otherwise I am at a loss. Plants in the dark not only do not absorb CO2, they produce it, and in addition compete with the fish for O2, which sort of would explain the heavy breathing you observe (I assume first thing in the AM). But with your 3 airstones going would not expect your fish to be symptomatically hypoxic due to plants which they act like they are. Despite your 3 air stones you may actually have to increase aeration when dark, or reduce plants. My plan is to put bubble curtain walls along both sides of the my tanks to run at night to minimize this potential problem as I love planted tanks, but I have high tanks. You are always going to have some variance of ph, but I am surprised it reaches 0.5 as CO2 dissipates rapidly from liquid into atmosphere. How tightly sealed is your tank top? What kind of filter do you run that would drop your tap ph from 8 to 7.5? That it goes up to 8.5 is due to offgassing CO2. Also just to be clear, your ph recovers in the morning before your water change, or is it the water change that raises the ph from the night before?

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Hi Don,

My top of tank has lids, but plenty of gaps to allow for gas exchange etc. The filter is just a carbon/sediment cartridge filter. No the Ph seems to follow the pattern of decrease and increase regardless of WC's.

I've been testing and documenting the water and doing some experiments this week.

I added a handful sized bag of crushed coral to the filter this week, can't say I have noticed a difference. I may add more in future, just wanting to make small changes over time to minimise stress. I removed half of the potted plants on Thursday, with no measurable difference of Ph swing pattern. I measured the PH daily at 3pm before any waterchange and it was at 8.1. I have also dropped to a 30% WC of unaged water, daily while the lights are still on. This ensures the water I am changing and adding is the same PH. Today (friday) I have removed the remainder of the potted plants, leaving only a few small java ferns, anubias and mosses/algae that is on the driftwood. I will test the PH tonight and monitor for the next few days to see if the PH stabilizes at all.

I should also note for comparison, that my outside turtle pond (about 1000L) has a consistent Ph of around 8.2, and TDS of around 800. There is about 30kg of crushed coral in the pond, with bugger all plants as they eat it. This probably gets two large water changes per month, sometimes not even that. Its never seen a siphon, and doesn't get any pre-filtered water. (I just dose prime).

One thing that confuses me here is that your ph drops with lights off generally in a planted tank or if your running co2 your ph would go up, have you tried running your lights longer say 12hr a day so that more co2 is consumed during the day which would in turn lessen the swing

Jeanne

Well more co2 is present when lights are off because plants are not consuming it, but also releasing it, as are the fish.
Then as it is consumed during the day, the PH rises. I have confirmed tonight that there is much less swing in PH with majority of plants removed from the tank. I will monitor this over the next few days for consistency.

Brendan, with CO2 users, there seems to be some debate regarding whether pH swings associated with fluctuating levels of CO2 are as harmful as lowered pH from other sources. I don't know why the nature of the conjugate base would have any impact on the effects of fluctuating pH. When I get my tanks set up I want a lot of plants but do not intend to test the effects of daily pH fluctuations. Regardless, pushing your kH up will lower the degree of pH fluctuation but the "fix" is to either reduce the number of plants, add CO2 during the day, or increase offgassing by increasing surface area either with more airstones, &/or adding a sump, &/or adding wet/dry filtration, &/or fluidized filter &/or spray bar for water return. My tank design includes all of these, I like redundancy.

Plants will not flourish in that PH. Generally a PH of 5.5 - 6.5 but can go a bit higher. Usually not higher than 7.5 and some plants even have a difficult time taking up nutrients in that PH.

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Originally Posted by bluelagoon

Plants will not flourish in that PH. Generally a PH of 5.5 - 6.5 but can go a bit higher. Usually not higher than 7.5 and some plants even have a difficult time taking up nutrients in that PH.

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No argument in re aquarium plants in general but at the same time the 0.5 ph swing indicates that whatever type of plants he has, they are metabolically active suggesting good health. Brendan, purely for my curiosity, once you pulled the plants, did your ph trend closer to 8 or 7.5?

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Originally Posted by dspeers

No argument in re aquarium plants in general but at the same time the 0.5 ph swing indicates that whatever type of plants he has, they are metabolically active suggesting good health. Brendan, purely for my curiosity, once you pulled the plants, did your ph trend closer to 8 or 7.5?

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Hi Don,

The tank only drops to about 7.9-8.0 at night, and peaks at about 8-8.1 during the day.

Quote:

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Originally Posted by bluelagoon

Plants will not flourish in that PH. Generally a PH of 5.5 - 6.5 but can go a bit higher. Usually not higher than 7.5 and some plants even have a difficult time taking up nutrients in that PH.

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What’s the theory behind that Merv? I ask because I’ve always had plants grow and flourish in that PH range, I’m currently trimming about 3ft of growth off my vallisneria each month and I recently had my swords produce about 40 pups.

So basically your ph swing was due to an accumulation of CO2 when dark rather than exuberant photosynthesis raising your ph during the day. If you are satisfied with plant growth then the first problem can be addressed by increasing the effective water surface area. Had it been the second issue, would have either required adding CO2 during the day or keeping the plant biomass way down as you have already done. My understanding of the negative effects of alkaline water on plant growth is that several important nutrients, Iron, Calcium, etc. become less soluble as ph goes up causing deficiencies.

Quote:

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Originally Posted by dspeers

So basically your ph swing was due to an accumulation of CO2 when dark rather than exuberant photosynthesis raising your ph during the day. If you are satisfied with plant growth then the first problem can be addressed by increasing the effective water surface area. Had it been the second issue, would have either required adding CO2 during the day or keeping the plant biomass way down as you have already done. My understanding of the negative effects of alkaline water on plant growth is that several important nutrients, Iron, Calcium, etc. become less soluble as ph goes up causing deficiencies.

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Ok, so increasing the effective surface water area means either a wider tank or sump? How does this affect it?

My end goal is to be able to have plants, with minimal PH swing.

Quote:

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Originally Posted by bluelagoon

Plants will not flourish in that PH. Generally a PH of 5.5 - 6.5 but can go a bit higher. Usually not higher than 7.5 and some plants even have a difficult time taking up nutrients in that PH.

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I kind of disagree with you here Merv as all of my tanks are planted my lowest ph being 6.8 and the highest being 7.2 I target feed on the initial startup of a tank but nothing afterwards I do not run co2 I run my lights 12hr a day and my plants are flourishing I think it comes down to fine tuning a tank, generally you can do a 30% water change with no adverse effects on ph

Jeanne

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Originally Posted by Sturiosoma

I kind of disagree with you here Merv as all of my tanks are planted my lowest ph being 6.8 and the highest being 7.2 I target feed on the initial startup of a tank but nothing afterwards I do not run co2 I run my lights 12hr a day and my plants are flourishing I think it comes down to fine tuning a tank, generally you can do a 30% water change with no adverse effects on ph

Jeanne

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Plants will grow in that range. Not too high. My water is soft, is similar to yours. They would do much better between 5.5-6.5. but a few degrees on side or the other and most plants will do ok (5.0-7.5). But 8, I don't think you'll find many fresh water plants that can handle that much alkalinity. I see nutrient imbalance.

oops double post

Off-gassing the excess CO2 produced by the plants overnight first requires sufficient water circulation in the tank to avoid a concentration gradient, but with any reasonable flow (which you have with two canister returns) that should not happen. Your rate limiting step for removing CO2 is the total surface area between water and air. All aeration does is increase this interface by the size and number of the bubbles, same goes with either a fluidized biofilter https://www.youtube.com/watch?v=U9ovPRxMWk8 or a wet/dry chamber https://lovefishtank.com/wet-dry-sump-filter/ Since I am using both, I have a filter pad in the base of the box and use K-1 media in the fluidized filter. Adding a spraybar to the canister or sump filter return increases surface area, drilling a bunch of holes in the top of sump chamber separators to break up flow increases area. The fastest and easiest steps for you are to increase aeration with increased stones or bubble curtains, only need to run when lights off so aesthetics not an issue and add spraybars to your cannister returns. Reintroduce all the plants and see where you are at. If that still fails then would consider adding a sump. If you like your tank, that would be the last thing I change.

Hi Don,

Thanks for your help, sorry I thought I had already replied to you. I've added some aeration, more crushed coral and just two pots of val to the tank. I'll monitor this and see what happens.

What is your rational for adding crushed coral for an already high KH and PH? Never heard of doing it on those water parameters for discus.

That may be my fault. I indicated that increasing the Kh would reduce the ph swings at night. In addition he indicated that his Kh was 5-6 which is a little low in what I understand is proper Discus range 4-8.

There are still things about this tank that confuse me or I did not ask but should have. Given that he was able to stabilize the pH I kinda backed off, I can be a little OCD and did not want to be a PITA;) The biggest puzzle is that to my understanding unless tank circulation is very low or top is tightly sealed or tank design has very small air/water interface or Kh is under ~3.5, pH should not move by ~0.5 without supplemental CO2. Unfortunately none of these situations apply and I am concerned that I am still be missing something.

1. Why does his mechanical/Carbon filter drop the tap water pH from 8 to 7.5, not particularly important, but weird.
2. The pH in the aging barrel at 48 hours is 8.5, is that also heated or still substantially colder than the aquarium temp. If colder still supersaturated with CO2. Not that important in this case but the colder the water the higher the risk of "microbubbles"
3. Did you verify your Kh test results, and more importantly when did you test relative to your water change? If just post water change you do not know if that represents a swing of as low as zero or you added new water with a Kh of 10 to tank water with a Kh of 2. Would be advantageous to test the kH of the aging barrel and tank both just prior to a water change.

The implications of a wide swing is that your Kh is being consumed by another source of acid, probably NO3. So what is your nitrate level? Given that your pH varied more with day vs night than with water change I would be surprised if your NO3 is high but as mentioned your tank is confusing. If your Kh difference between barrel and tank is low this should also be low, but better to verify. Again testing both the barrel and tank just prior to a water change would be most informative.

If your Kh variance is low and is indeed 5-6, I agree with Mervin, raising it offers no substantial benefit, but in fairness changing the Kh from 5 or 6 to only 8 should not increase pH by all that much. If your Kh has major swings you have a different problem with a different solution and the plants are a diversion. But, the fact that removing plants fixed the problem should mean this is CO2 and only CO2.

Quote:

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Originally Posted by bluelagoon

What is your rational for adding crushed coral for an already high KH and PH? Never heard of doing it on those water parameters for discus.

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Hi Merv,

Just in previous discussion with Don, it was basically just experimental to buffer PH to see if that would reduce swing, with plants back in tank.

Quote:

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Originally Posted by dspeers

That may be my fault. I indicated that increasing the Kh would reduce the ph swings at night. In addition he indicated that his Kh was 5-6 which is a little low in what I understand is proper Discus range 4-8.

There are still things about this tank that confuse me or I did not ask but should have. Given that he was able to stabilize the pH I kinda backed off, I can be a little OCD and did not want to be a PITA;) The biggest puzzle is that to my understanding unless tank circulation is very low or top is tightly sealed or tank design has very small air/water interface or Kh is under ~3.5, pH should not move by ~0.5 without supplemental CO2. Unfortunately none of these situations apply and I am concerned that I am still be missing something.

1. Why does his mechanical/Carbon filter drop the tap water pH from 8 to 7.5, not particularly important, but weird.
2. The pH in the aging barrel at 48 hours is 8.5, is that also heated or still substantially colder than the aquarium temp. If colder still supersaturated with CO2. Not that important in this case but the colder the water the higher the risk of "microbubbles"
3. Did you verify your Kh test results, and more importantly when did you test relative to your water change? If just post water change you do not know if that represents a swing of as low as zero or you added new water with a Kh of 10 to tank water with a Kh of 2. Would be advantageous to test the kH of the aging barrel and tank both just prior to a water change.

The implications of a wide swing is that your Kh is being consumed by another source of acid, probably NO3. So what is your nitrate level? Given that your pH varied more with day vs night than with water change I would be surprised if your NO3 is high but as mentioned your tank is confusing. If your Kh difference between barrel and tank is low this should also be low, but better to verify. Again testing both the barrel and tank just prior to a water change would be most informative.

If your Kh variance is low and is indeed 5-6, I agree with Mervin, raising it offers no substantial benefit, but in fairness changing the Kh from 5 or 6 to only 8 should not increase pH by all that much. If your Kh has major swings you have a different problem with a different solution and the plants are a diversion. But, the fact that removing plants fixed the problem should mean this is CO2 and only CO2.

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I've only got a fairly basic understanding of co2 in that, concentrated co2 at night will drop PH, and it will rise back up during the day as the plants consume the co2. Interestingly a few planted tank forums suggest that a swing in PH over several hours does not affect the fish and will not stress them - however this was not in relation to discus so I sort of disregarded that. (This is just from my research).

I have monitored other tanks/ponds that I have, and my turtle pond stays at a steady PH, regardless of day or night - it has little to no plants as they eat them. It gets all the same water that my discus tank does.

Hi Don, Nitrates are always at 5, never higher (at the time of testing of course)

Ok so just an update, I think I have fixed the problem! Yay!

After adding the 2 bags of crushed coral,and 4 airstones running 24/7 I've been able to add most of the plants back in, and only have around 0.1 PH swing at most in a 24 hour cycle.
For my water changes, I am filling the aging barrel about an hour or so prior to the WC (to match the PH in the tank) with vigorous aeration from a 3000 LPH powerhead. It is also filled quite fast helping to disperse some gas off. In this time I also add the prime to ensure it has locked up the ammonia in the tap water until my BB in the tank eats it. So for now, this seems to be the fix and hopefully stays that way.

Thanks to everyone for your help and input! I never thought I would learn so much about water chemistry when taking on discus. I do find it very interesting though!

cheers