Newly cycled tank PH Crash Mystery

Hi, I am looking for some advice on a mystery (to me) going on with my newly cycled, 75-gallon, planted tank. Apologies for the long post, but it should provide the pertinent information to describe the situation.

Typical tank parameters:
77.8 degrees
GH: 10
KH: 6-7
PH: 7.6

Tap Water:
GH: 10-11
KH: 7
PH: 7.6

I dose about 4 mL ThriveC once a week for my plants.

Fishless tank cycle completed (2 days at 0 Ammonia; 0 Nitrite; w/Nitrates present) on 11/17/2019. I do my testing in the morning, so I was able to do a water change (75%), add fish, and maintain plants on that same Sunday evening.

Added the following livestock:
3 Green Swordtails
6 Neon Tetras
2 Speckled Catfish
2 Nerite Snails

I also added a piece of mopanI driftwood with my existing java ferns replanted from the same tank. Nitrates post-water change was less than 5 ppm. Everything looked great.

Note:
MopanI was soaked and boiled until tannins were light tea-clored prior to placing in the tank.
Also, I ordered plants scheduled to arrive Saturday, but due to weather concerns, they did not arrive until Tuesday. I decided not to wait for them before stocking as trips to the LFS are easiest on the weekend.

A PH crash occurred overnight. Monday morning PH was 6.6. During the crash, GH was 10, but KH dropped to 4. Over the next 24 hours I lost 4 neons. The tank PH re-stabilized at 7.6. Ammonia, Nitrites, and Nitrates continue to look normal.

Received and added the plants on 11/19/2019.

Corkscrew vallisneria, leopard vallisneria, flame sword, and cryptocoryne wendtiI green. My tank is between 35-40% planted at this point.

Although I suspected the mopanI may have caused the PH crash, I really have no idea. But, not great news over the next week.

My current best guess is the PH crash may have killed off some/most of my beneficial bacteria. Ammonia has been climbing for a few days with no Nitrites and unchanged Nitrates around 10 ppm. I did a water change on Sunday (11/24) to bring ammonia down. Post-water change nitrates was 5 ppm.

I began treating this situation like a fish-in cycle. I dose with ammolock and do water changes as needed. I decided not to dose ThriveC until the tank is stable. The other tank parameters appeared to be stable. PH--7.6 for six days. Other parameters: GH:10/KH:5-6 (reasonably close to tap water).

Then, yesterday, I had another PH crash. PH was 6.6. I am really stumped now. The only thing I have done since I did the water change on Sunday is add Ammolock to detoxify ammonia.

11/26/2019 parameters:
Ammonia: 1 ppm
Nitrite: 0 ppm
NItrate: 10 ppm
PH: 6.6

I also tested GH/KH once I realized the PH crashed:
KH: 3-4
GH: 11

One of my fish had a red gill on her left side and she was racing up and down the side of the tank. Because of the sick fish, I changed out 10 gallons before work. Post water change readings were:

Ammonia: .5 ppm
PH: 7.0

That evening, I checked parameters again.
Ammonia: 2 ppm
Nitrite: Trace
Nitrates: 10-20 ppm
PH: 6.6

I did a 25 gallon water change. I will check tank parameters again once the tank settles.
Note: Fish were a little lethargic, but perked up after the water change. I have no idea if it is the PH or the Ammonia or both.

Post water change parameters:
Ammonia: 1-2 ppm
Nitrates: 5 ppm
PH: 6.8

Added Ammolock.

This morning the test parameters were:
Ammonia: 4 ppm
Nitrite: .25 ppm
Nitrate: 10 ppm
PH: 6.6

Did an 18-gallon water change before work. Checked parameters about 30 minutes later:

Ammonia: 2 ppm
Nitrite: .25 ppm
Nitrate: 5 ppm
PH: 6.8

Added Ammolock to reduce toxicity. I plan to do another water change tonight.

May or may not be relevant:
Very notable plant growth the last few days. The flame swords I planted last week have new submerged leaf growth and my ludwigia repens is visibly taller/lusher in a couple of areas. Not sure what, if any, impact the plants may have on the situation--this is my first planted tank.

Any thoughts on why my PH is crashing?
Thus far, I have not lost any additional fish, but I did lose 1 Nerite snail a few days ago--right as the ammonia started to creep up.

 

What is your substrate?

 

Eco-Complete 60%
Black gravel 25%
Black Sand 15%

If helpful, I took this picture this morning right after the water change.

 

Do you use CO2 on the tank?

 

No CO2.

 

Ph change at night and day of a growing planted tank is normal.

 

I don't understand what causes something like this but you may want to consider adding crushed coral to your filter. Put some in a media bag and place it in your filter. If there is no room in the filter, hang the bag so that water is running through it. It should stabilize your PH up to the same as your source water. It isn't going to happen instantly so give it a few days. If the PH is still dropping add more CC.

 

Your PH now really isn't swinging that wildly. When you have a planted tank their is a natural co2 and oxygen exchange going on from the plants which will swing your PH mildly. If you're going from 6.6 to 7.6, then that's a problem....but 6.6 to 6.8 to 7 is nothing crazy. I actually inject c02 and I had gotten a digital PH thermometer and my PH changes from night to day. The distress your fish are showing are more likely from the ammonia. I would focus on water changes to keep your ammonia under control and just make sure your KH doesn't get too low because that will fluctuate PH...but your KH is in a normal range right now.

 

If you will switch your water conditioner from ammo-lock to prime you should be able to get your ammonia back down to zero. Some claim that ammo-lock and prime do the same thing. Ammo-lock locks up ammonia. Prime detoxes ammonia. Both products protect your fish from the damaging affects of ammonia but when using prime the bacteria soon clears up the ammonia whereas the ammonia reading while adding ammo-lock just keeps rising.

I base this on reading so many reports from folks right here on this forum who are seeing what you are seeing right now.

 

MissPanda (quoter is not working )
My stable PH (for the 5 week fishless cycle period) prior to this incident is 7.6. Between the two crashes, it was 7.6 for six days. The recent 6.6 to 6.8/7.0 fluctuations during the PH crash are just due to the water changes I am doing to reduce ammonia and nitrite. Does your advice still hold? It is the drastic nature (and lack of pattern) of the swing that worries me.

I am staying on top of water changes as much as possible. These fish are great fun and I would be bummed to lose them.

mattgirl
I ordered Prime to replace my API maintenance products. I had already purchased the Ammolock as a holdover from my fishkeeping 10,000 years ago before reading the more recent great Prime recommendations. It arrives Friday.

 

MissPanda (quoter is not working )
My stable PH (for the 5 week fishless cycle period) prior to this incident is 7.6. Between the two crashes, it was 7.6 for six days. The recent 6.6 to 6.8/7.0 fluctuations during the PH crash are just due to the water changes I am doing to reduce ammonia and nitrite. Does your advice still hold? It is the drastic nature (and lack of pattern) of the swing that worries me.

I am staying on top of water changes as much as possible. These fish are great fun and I would be bummed to lose them.

Plants will lower kh, although I'm not sure if they lower KH super fast like in your case. KH affects PH so you want to keep your KH 4-8 is good. Your water changes are already doing that. Your PH right now is neutral. Are you trying to get it back up to 7.6? My Ph goes from 6.8 to 7.2 all the time with no visible distress to my fish. You changed your chemistry with adding all the fish and plants so now everything is in a process of stabilizing. Help it along with the water changes to stabilize your cycle. Your PH should stabilize along with it.

 

Plants will lower kh, although I'm not sure if they lower KH super fast like in your case. KH affects PH so you want to keep your KH 4-8 is good. Your water changes are already doing that. Your PH right now is neutral. Are you trying to get it back up to 7.6? My Ph goes from 6.8 to 7.2 all the time with no visible distress to my fish. You changed your chemistry with adding all the fish and plants so now everything is in a process of stabilizing. Help it along with the water changes to stabilize your cycle. Your PH should stabilize along with it.

I am not trying to change my stable tank PH. My tap PH is 7.6, so when I do the water changes (depending on how large), it is bringing up the PH a couple of tenths. Fingers crossed, it stabilizes. Better for me if it stabilizes near my tap PH, but I'll cross that bridge when I get there. Hopefully, the water changes will do their thing and it will level out soon.

 

mattgirl
I ordered Prime to replace my API maintenance products. I had already purchased the Ammolock as a holdover from my fishkeeping 10,000 years ago before reading the more recent great Prime recommendations. It arrives Friday.

Good job Once you switch to Prime you should start seeing your ammonia going to and staying at 0. You may have missed my post about the crushed coral. It may not be necessary longterm but it should help now. It should stabilize your PH long enough for whatever is causing the drastic drop to stabilize. I do consider the drop from 7.6 to 6.6 too drastic a drop. Right now you are controlling it somewhat with water changes but if you will add the crushed coral it should stay close to the same as your source water.

 

I have a follow up specific question. My tank was cycled. What happened to my beneficial bacteria? Did the initial PH crash kill them? My tank was processing 1-2 (conservatively) ppm of ammonia prior to adding the fish. Nothing I can do now, but I would like to understand to avoid the situation in the future. Right now, I am essentially managing a fish-in cycle, but I never intended to place this stress on my fish.

Good job Once you switch to Prime you should start seeing your ammonia going to and staying at 0. You may have missed my post about the crushed coral. It may not be necessary longterm but it should help now. It should stabilize your PH long enough for whatever is causing the drastic drop to stabilize. I do consider the drop from 7.6 to 6.6 too drastic a drop. Right now you are controlling it somewhat with water changes but if you will add the crushed coral it should stay close to the same as your source water.

I have a canister filter. I am a little scared to open it up and dislodge the beneficial bacteria colony. Do you recommend doing that during the current crisis? Given the BB die-off, I experienced, I am really concerned about killing my bacteria accidentally....

 

I have a follow up specific question. My tank was cycled. What happened to my beneficial bacteria? Did the initial PH crash kill them? My tank was processing 1-2 (conservatively) ppm of ammonia prior to adding the fish. Nothing I can do now, but I would like to understand to avoid the situation in the future. Right now, I am essentially managing a fish-in cycle, but I never intended to place this stress on my fish.

You added too many fish at once so your cycle couldn't keep up. Did you clean your filter at all? If you didnt touch your filter, whatever you had is still there.

 

I have a canister filter. I am a little scared to open it up and dislodge the beneficial bacteria colony. Do you recommend doing that during the current crisis? Given the BB die-off, I experienced, I am really concerned about killing my bacteria accidentally....

I am not sure it was a die off. It is possible that you didn't grow enough bacteria to handle the bio-load of the fish you added. More bacteria had to grow to keep up with the amount of ammonia they were producing.

Opening the filter isn't going to dislodge the bacteria. It is growing on every surface in the filter and on everything in your tank. If you still aren't comfortable opening it just put some crushed coral in a media bag and hang it so the water going back in your tank runs through it or where the filter pulls water out of the tank. You want water circulating through it so it disperses throughout the tank.

There are products designed to adjust the PH but I've never used any of them so am not at all comfortable recommending something I don't have first hand experience with. I both use and recommend crushed coral.

 

You added too many fish at once so your cycle couldn't keep up. Did you clean your filter at all? If you didnt touch your filter, whatever you had is still there.

I did not touch my filter. Canister filters are new to me, so I wanted to leave that until the tank is well-established before I clean it for the first time if possible. If needed, I will of course, clean it. It is a Penn-Plax 1200.

How many should I have added for future reference? Any rough guide is fine. I get they all have different bioloads. I have seen recommendations all over the map. I have a 75 gallon tank. Specifically, I added:

3 swordtails
2 pepper corys
6 small neons (4 of which died in 24 hours during the PH crash)
2 Nerite snails

That was a large load and I am not surprised the ammonia spiked a little. I just figured it would be a gentler swing...

 

MissPanda (quoter is not working )
My stable PH (for the 5 week fishless cycle period) prior to this incident is 7.6. Between the two crashes, it was 7.6 for six days. The recent 6.6 to 6.8/7.0 fluctuations during the PH crash are just due to the water changes I am doing to reduce ammonia and nitrite. Does your advice still hold? It is the drastic nature (and lack of pattern) of the swing that worries me.

I am staying on top of water changes as much as possible. These fish are great fun and I would be bummed to lose them.

Your pH swings may be because of the Ammolock. There are acidic byproducts when using Ammolock and it will lower pH slightly because of the chemical composition of the product. I agree with mattgirl about switching from Ammolock to Prime. Although Ammolock does the same thing to ammonia (converts it to ammonium temporarily) the chemicals it uses result in ammonium that isn't as bioavailable to bacteria as the ammonia/ammonium conversion that occurs with Prime and ammonia is more persistent in cycling tanks using Ammolock. It's fine for protecting fish in a well cycled tank with a sudden ammonia/nitrite spike but not that great for a cycling tank IMO. Try switching to Prime first. Your pH/KH may stabilize on its own in the absence of Ammolock and you may not need the crushed coral.

 

BTW, thank you all for sharing your expertise. Super helpful and I really appreciate it (as do my fish!).

 

I did not touch my filter. Canister filters are new to me, so I wanted to leave that until the tank is well-established before I clean it for the first time if possible. If needed, I will of course, clean it. It is a Penn-Plax 1200.

How many should I have added for future reference? Any rough guide is fine. I get they all have different bioloads. I have seen recommendations all over the map. I have a 75 gallon tank. Specifically, I added:

3 swordtails
2 pepper corys
6 small neons (4 of which died in 24 hours during the PH crash)
2 Nerite snails

That was a large load and I am not surprised the ammonia spiked a little. I just figured it would be a gentler swing...

Yeah everyone does it different, for me I add each species at a time, unless I was going to put a lot of one species then I'd break it up.

 

I am not sure it was a die off. It is possible that you didn't grow enough bacteria to handle the bio-load of the fish you added. More bacteria had to grow to keep up with the amount of ammonia they were producing.

Opening the filter isn't going to dislodge the bacteria. It is growing on every surface in the filter and on everything in your tank. If you still aren't comfortable opening it just put some crushed coral in a media bag and hang it so the water going back in your tank runs through it or where the filter pulls water out of the tank. You want water circulating through it so it disperses throughout the tank.

There are products designed to adjust the PH but I've never used any of them so am not at all comfortable recommending something I don't have first hand experience with. I both use and recommend crushed coral.

Okay, I will find some crushed coral and get that rolling.

Your pH swings may be because of the Ammolock. There are acidic byproducts when using Ammolock and it will lower pH slightly because of the chemical composition of the product. I agree with mattgirl about switching from Ammolock to Prime. Although Ammolock does the same thing to ammonia (converts it to ammonium temporarily) the chemicals it uses result in ammonium that isn't as bioavailable to bacteria as the ammonia/ammonium conversion that occurs with Prime and ammonia is more persistent in cycling tanks using Ammolock. It's fine for protecting fish in a well cycled tank with a sudden ammonia/nitrite spike but not that great for a cycling tank IMO. Try switching to Prime first. Your pH/KH may stabilize on its own in the absence of Ammolock and you may not need the crushed coral.

Wow, I had no idea. I will ditch the Ammolock as soon as the Prime arrives. Thank you!

 

Okay, I will find some crushed coral and get that rolling.



Wow, I had no idea. I will ditch the Ammolock as soon as the Prime arrives. Thank you!

Let us know how your pH/KH/ammonia behave after you ditch the Ammo and start using the Prime okay?

 

Check in:
Ammonia is still spiking daily. Nitrites is appearing too. I have been doing 60+% water changes daily to keep ammonia down. Received the Prime yesterday evening. Dosed the tank last night and completely ditched API products this morning when I did a 65% water change. Hopefully, it is Prime for the win.

Slightly new development. The tank has gone from slightly cloudy to extremely cloudy the last 2 days. Water changes clear it up temporarily, but the water gets cloudy again quickly. Ignoring the cloudiness for now--just trying to keep ammonia under control, but putting it in the record for future reference.

Current parameters (post water change today):
Ammonia 1-2 ppm
Nitrite < .25
Nitrate < 5 ppm
PH: 7.6

Minor PH variations are still present, but these can probably be attributed to frequent water changes. Fingers crossed the tank is on the road to stability. Will keep all of you posted. I truly appreciate your help!

 

It is almost like your cycle didn't get started until you added fish. Strange that happened since it was processing 2ppm ammonia before adding them.

I am hoping now that you have stopped adding the ammo-lock your bacteria will be getting well fed and will soon get in high gear. It sounds like you are experiencing a bacterial bloom. Not a problem but just looks bad until it clears up.

 

It is almost like your cycle didn't get started until you added fish. Strange that happened since it was processing 2ppm ammonia before adding them.

Right? That is what initially had me scratching my head. I like to think I did my homework, but part science and part art I guess? You all have me back on track, so this too will pass.

I am hoping now that you have stopped adding the ammo-lock your bacteria will be getting well fed and will soon get in high gear. It sounds like you are experiencing a bacterial bloom. Not a problem but just looks bad until it clears up.

Thanks for the reassurance. As long as it is mainly harmless, I can address when the main issue is resolved. It makes snail hunting an adventure. He is good at hide and seek the way it is. LOL

 

Latest check-in: Ammonia is 0 ppm. Spiked Nitrites for a couple of days, but I think it is leveled off/falling (will know for sure tomorrow). The tank cloudiness is clearing up...still a little cloudy, but far better than the impenetrable fog from a few days ago.

PH has been stable at 7.6 for a few days now. Not sure if I will need the crushed coral, but if anyone still thinks otherwise, I will still consider.

Hoping the next time I report I will have a stable tank.

 

Latest check-in: Ammonia is 0 ppm. Spiked Nitrites for a couple of days, but I think it is leveled off/falling (will know for sure tomorrow). The tank cloudiness is clearing up...still a little cloudy, but far better than the impenetrable fog from a few days ago.

PH has been stable at 7.6 for a few days now. Not sure if I will need the crushed coral, but if anyone still thinks otherwise, I will still consider.

Hoping the next time I report I will have a stable tank.

Great news As long as your PH is staying stable at 7.6 I don't think you will need the crushed coral.

 

Good news! Today is Day 2 with no ammonia or nitrite and day 7 with stable PH. My tank is mostly clear and the fish all appear healthy! I am now part of the Prime cult.

Appreciate the forum members who offered advice. Thank you!!! A couple gratuitous pictures attached.

 

Fantastic news. Just let your numbers be your guide as to how much water needs to be changed weekly and above all else--Have fun now that the stressful part is behind you.