Mysterious Fish Deaths and Rising pH

[Chris C.]

Hey all,

I'm a High School, Special Education, Biology teacher. There's a LOT of backstory to my tank, but I'm gonna skip most of it (brief description at the end of these paragraphs), since it's not relevant to the current set up.

I started the tank back in EARLY November, 2022. I put the plants in shortly after set up. I put an Amano Shrimp in roughly 2 weeks later, because ammonia/nitrite/nitrate levels were consistent. The shrimp disappeared (never found a body, and there was JUST enough space between the lid and the filter that it could have climbed out). I continued to allow the tank to cycle, then put fish in in EARLY January, after we returned from Winter Break and things were still testing fine.

I had to miss 3 weeks of work shortly after putting in the fish because of a family emergency that took me 400+ miles away from my classroom (my Dad was suddenly very sick, then passed away). I came back and things were still fine (I had another teacher do feedings and send me occasional pictures/videos), other than 1 tetra that looked off, but I couldn't identify what was wrong before it passed away. NONE of the other tetra looked to be in a similar state and they're all fine now. Also saw no similar signs on the guppies. I figured I just got 1 older tetra in the bag, and it was their time.

Then, about a week and a half after I got back the female fry that had snuck into the bag when I got the guppies disappeared. I figured she was getting bullied by the males. I was out on Friday, 2/24, and had put some towels around the tank in case of a power outage due to expected terrible weather on 2/23, just in case (to provide some extra insulation). When I got back on Monday, 2/27, the 2 males had disappeared.

Over time, the water level in the tank had been dropping, so I set up some water to add to the tank to do a small water change (after my extended absence, it hadn't seemed necessary, since there was no sign of disease in the tank). This seems to be where the pH problem started. I treated the water I was planning to add, got it to a 7.2 pH and matching temperature and then ran out of time before having to leave the room for my next class, so I added the water after taking just a bit more out. That was Monday, 2/27.

Starting 2/28, the tank pH spiked to 8.2. Every day (except today, & over the weekend when I don't have access to the tank), since then I have had to repeatedly bring the tank pH back down to 7.4, but it keeps spiking back up. I've used extra water from the change the day before to try to lower the pH, then, when I was out of that, I took water out of the tank to treat to bring the pH back down slowly/carefully.

Now I have a 3rd dead male guppy (found the body this time). 1 of the 2 remaining males appears bloated, but is swimming fine. The other male looks fine and so do all the tetra. I can't figure out WHY the pH is still spiking. 

When I had the tank at home during Distance Learning, it NEVER had a pH spike. After an incident last year where a student in another class (same room, different teacher) poured soap into the tank, I stopped and then restarted the tank (with locks on the lid) this year. No one but me and 2 other teachers have the lock codes (gave them the codes when I was out for 3 weeks). All chemicals for tank maintenance are in a LOCKED filing cabinet.

I don't know if this is a disease or if this is something I'm doing wrong.

Tank Plants:

• 1 Java Fern
• 2 Dwarf Saggitaria
• 1 plant that came from an LFS with a shrimp that I had in there a while ago, but that disappeared over Fall Break. Thought it was elodea, but it's way smaller.

Tank Inhabitants:

• 2 (formerly 3, and before that 5) Male Guppies (previously also had 1 female fry)
• 9 Neon Tetra (formerly 10)

Test Results

• pH: 8.4 (used to be stable at 7.4, keeps jumping to 8.4 after I get it back down to around 7.4 again). Tetra Test Strip gives consistent reading.
• Nitrates: 10ppm (stable) Tetra Test Strip gives consistent reading.
• Hardness: 8 drops/143.2. Tetra Test Strip reads between Hard and Very Hard
• Nitrite: 0ppm (stable) Tetra Test Strip gives consistent reading.
• Ammonia: 0ppm (stable) Tetra Test Strip gives consistent reading.
• KH/Buffer:  Off the API test chart. Tetra Test Strip indicates Very High (300+)
• Water Temperature: 78-79°F (stable)

[Guppysnail]

I’m sorry for your losses 

May I ask why you are adjusting ph?  Most fish readily adapt to almost any ph. The constant fluctuations are much more harmful than simply living in an “incorrect” ph. 

My ph runs 7.8-8.4 after it’s aerated (aerating raises ph as it knocks the carbon dioxide out of the water). Most of my fish are “supposed” to be 6.8-7.2 ph. They thrive and their babies thrive. I add only dechlorinator to my tap water. 
 

[Chris C.]

I'm adjusting pH because it randomly spiked after the water change. My understanding is that a pH that is too high can mess up fish slime coats and make it so they get sick more easily. I wasn't doing anything to adjust the pH prior to the spike and would VERY much prefer NOT to keep messing with it.

[Colu]

What I would do is test your tap waters pH by putting it in a bucket with an air stone for 24hr to allow it to off gas that will give you an accurate reading for your pH @Chris C.

[Chris C.]

I'll try that! What I'm confused about is the pH continuing to spike up in the tank from a 7.4 to an 8.4 overnight when I haven't added any new water from the tap. Anyone know what could be causing that?

[Colu]

On 3/6/2023 at 8:52 PM, Chris C. said:

I'll try that! What I'm confused about is the pH continuing to spike up in the tank from a 7.4 to an 8.4 overnight when I haven't added any new water from the tap. Anyone know what could be causing that?

What substrate are you using and did your add any rocks that could be releasing mineral that could be raising your pH 

[Chris C.]

Substrate is the old substrate from my previous set up (before the tank got soaped last year). There have been no changes to the substrate since I set the tank up fresh again this year (I did THOROUGHLY wash it before setting the tank up with the old substrate). I'd had some crushed coral mixed in with the substrate, but, again, there were no changes to the substrate made. No new anything in the tank, other than the water I'd added, which should've been at a pH of 7.2 (which is what the new water was at when I tested it before adding it to the tank).

[Colu]

On 3/6/2023 at 9:26 PM, Chris C. said:

Substrate is the old substrate from my previous set up (before the tank got soaped last year). There have been no changes to the substrate since I set the tank up fresh again this year (I did THOROUGHLY wash it before setting the tank up with the old substrate). I'd had some crushed coral mixed in with the substrate, but, again, there were no changes to the substrate made. No new anything in the tank, other than the water I'd added, which should've been at a pH of 7.2 (which is what the new water was at when I tested it before adding it to the tank).

How much crushed coral did you add 

[Chris C.]

On 3/6/2023 at 3:05 PM, Colu said:

How much crushed coral did you add 

I don't remember. My partner and I added it back when the tank was at our home when the school was shut down due to COVID. This is year 2 of us being back at the school. 

[Colu]

On 3/7/2023 at 2:34 AM, Chris C. said:

I don't remember. My partner and I added it back when the tank was at our home when the school was shut down due to COVID. This is year 2 of us being back at the school. 

Looking at your water parameters as you have very high KH I would expect you to have a high pH what could be happening is that your tap water could have a lower pH when you do a water it temporarily lowers your pH before it shoots back up again or you have some hardscrape that raising your pH I think the large swings in your pH are more than likely what has been killing some of your fish 

[Lennie]

On 3/6/2023 at 9:56 PM, Chris C. said:

pH: 8.4 (used to be stable at 7.4, keeps jumping to 8.4 after I get it back down to around 7.4 again). Tetra Test Strip gives consistent reading.

Well, I am not sure about that one, especially if you are using the app. The colors are really hard to tell in those ranges on test strips too, in my opinion.

I've tried it multiple times both in a row and in different times. Tetra test strip ph readings were not consistent in my case, not even once. Once it has shown that I have 9.3 ph. Meanwhile I only had 8.0. It showed me between 0-3 gh all the time when I had a consistent 6. This goes for majority of the readings from my own experience. I have realised these when I had a chance to compare the inconsistent stats to liquid test kit readings.

If you have a chance, I would advice to try it with a reliable liquid test kit just in case. I'm using sera one, and I'm pretty happy about it. I guess API is more common in US.

[Chris C.]

On 3/7/2023 at 3:14 AM, Lennie said:

Well, I am not sure about that one, especially if you are using the app. The colors are really hard to tell in those ranges on test strips too, in my opinion.

I've tried it multiple times both in a row and in different times. Tetra test strip ph readings were not consistent in my case, not even once. Once it has shown that I have 9.3 ph. Meanwhile I only had 8.0. It showed me between 0-3 gh all the time when I had a consistent 6. This goes for majority of the readings from my own experience. I have realised these when I had a chance to compare the inconsistent stats to liquid test kit readings.

If you have a chance, I would advice to try it with a reliable liquid test kit just in case. I'm using sera one, and I'm pretty happy about it. I guess API is more common in US.

I usually only use the API liquid tests, the test strips are back up. 

On 3/7/2023 at 2:56 AM, Colu said:

Looking at your water parameters as you have very high KH I would expect you to have a high pH what could be happening is that your tap water could have a lower pH when you do a water it temporarily lowers your pH before it shoots back up again or you have some hardscrape that raising your pH I think the large swings in your pH are more than likely what has been killing some of your fish 

Water straight from the tap is an 8.2pH according to API liquid tests.

[Colu]

On 3/7/2023 at 4:55 PM, Chris C. said:

I usually only use the API liquid tests, the test strips are back up. 

Water straight from the tap is an 8.2pH according to API liquid tests.

Are you adding a buffer to lower your pH to 7.4 during water changes if you are that is only a temporary solution with your water hardness off the charts your  pH will go back to what tap waters pH is fairly quickly 

Edited March 8, 2023 by Colu

[Chris C.]

On 3/8/2023 at 4:15 AM, Colu said:

Are you adding a buffer to lower your pH to 7.4 during water changes if you are that is only a temporary solution with your water hardness off the charts your  pH will go back to what tap waters pH is fairly quickly 

What I don't get is that the pH has been stable in the mid 7s for months. The last time the pH was above 7.anything was 12/16/22 and 1/3/23 (last day of fall semester and 1st day of spring semester), and even then, it was only at an 8.0, then I got it back down to the 7s and it has stayed 7.4 consistently since then.

 

If it being at 8.4 isn't bad for the fish or the plants, I guess it doesn't matter. I just wish I knew why it suddenly spiked with no apparent cause (since it hadn't spiked like this before).

[Chris C.]

We lost the male guppy that had been looking bloated overnight.