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Discussion Starter · #1 ·
75 gallon tank
3 discus cichlids, 2 ghost knife fish, 5 bottom feeders, 5 zebra nerite snails
aquarium has been set up since Jan 1, 2011 and had been cycled
temperature is held at 82 but I raised it to 84
ammonia, nitrite and nitrate are all 0
pH was off the chart <5
I have had all the fish since May 2010 (except the snails), and have never had an issue.

Saturday, I bought the 5 zebra snails and introduced them slowly into the tank.
Sunday, I did a 50% water change as per my schedule (50% every other weekend, and 30% the weekends in between..). By this point, all the fish were normal and eating well.
Monday morning, I thought I saw bubbles on the knife fish (which happens after a large water change sometimes as my tap water is filled with air bubbles).
Monday evening, the 'bubbles' were still there so I decided to take a better look.. It almost looked as if the knife fish was peeling. I added more neutralizer hoping that would solve the issue.
Tuesday, the knife fish were 'peeling' in several areas along it's sides and parts of it's face. I tested the water and the only parameter that was off was the pH (<5). I thought the pH might have been like that for a while since I had just completed a 50% water change so I decided to hold off on any treatment.
Wednesday, both knife fish are dead, 5 bottom feeders dead, and two snails seem to be dead.. Every dead fish seems to have a light coloured film on them. My discus are struggling, huddled in the corner, dark in colour, and very scared..
I did a 30% water change, followed by a 50% water change. And I added a couple spoons of baking soda to raise the pH to 6.5. All other water parameters are perfect now. I have covered the aquarium with a blanket, and plan to not feed them or disturb them for 3-4 days.
Wise decision?
What else should I do?
Is it possible that the snails introduced a disease to my tank? Could it be fluke?
One of my discus has this odd white patch on his side behind his pectoral fin - parasitic?
I don't have a small tank to transfer the fish in to treat them. Is there anything I can do to treat my fish in the 75 gallon?

Thank you in advance!
 

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It's odd that your nitrates are reading 0, but you mentioned you just did a 50% water change.
What are you treating the water with, Prime, Aquasafe, etc?
Actually, you have a pretty rigorous water changing schedule; any particular reason why?
Did you test the water for ammonia and nitrites while the fish were dying off?
How are you getting oxygen into the tank? Where the fish gasping for breath?

It's possible that your pH crashed, thus killing all the inhabitants.
What is your pH straight out of the tap? What is your kH? If you don't have a proper buffering system, the pH can crash and can possibly kill fish. You mentioned that you added baking soda. Did you add it all at once? -If so, that could kill the remaining fish; a scale raise of 1.5 is pretty substantial. -If you need to raise the pH do so gradually, as in a few days. Obviously too late now.

You mentioned you added some new inhabitants. -Try to avoid adding any new additions in the future. I know you mentioned you don't have one but in the future, get a quarantine tank set up and place any new additions into the holding tank for a couple weeks. -If they are infected with anything, they will not introduce it into the community tank.

Due to the quick die-off, my best guess either water quality or stress. Check the water: ammonia, nitrites, nitrates, pH and kH. -If everything is okay then I suggest leaving the water alone and I would go another route and treat for a possible contagion or bacterial infection.
 

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While I don't think your water change schedule is out of the ordinary ( I try to do 50% each week in my tanks), pH less than 5 is pretty extreme even for discus. I wonder what is in your tank to make the pH plummet.

What is your tap water pH?

What do you use for dechlorinator?

Is there any chance a chemical containment (from a bucket, eg) could have gotten in the tank?
 

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Discussion Starter · #4 ·
All water parameters were in check before the fish started to die off, with the exception of the pH being less then 5.
I use Chloram-X to neutalize the tap water while doing my water changes.
I prefer this changing schedule as it keeps the algae in check. I had a lot of fish in the aquarium and one Fluval filtering the system. This schedule just seemed to work.. It has been working for almost a year.
I never had to test the ammonia and nitrites before as my water change schedule seemed to always keep it in check before..
I have an air stone. The fish never gasp.

pH out of the tap is around 8, and I treated a bit of water with the Chloram-X and that was also sitting around 8. I never tested my kH/GH..
Can the pH still crash if my water change schedule remains the same? I never had this problem before..
I did add all the baking soda at once. I understand this was a bold move, however I figured everything was under stress because of the sudden drop, and if anything, bringing the pH back to normal would help. Based on the sudden symptoms and die off of all the fish, I figured a sudden rise in pH would only help the situation.
Thursday morning - my last 3 discus were dead.. :(
I got the water tested. pH was back down to <5, ammonia was 0, and nitrates and nitrites were through the roof (probably due to the dead fish sitting in the aquarium over night)..

I thought of the chemical contamination possibility, but I never did anything different then my normal routine. It makes no sense to me.

Could the sudden spikes in pH be due to something in the city water? Maybe this recent spring meltdown has something to do with water GH/KH, thereby affecting the pH?
 

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City water treatment facilities will sometimes add extra chemicals to the water during different
weather conditions...it has happened here before.
So sorry for your loss, I had something similar happen to me a few years ago..
 

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Discussion Starter · #6 ·
I emailed the city water treatment facility, and they told me they haven't changed any of their treatments in the recent weeks.. So most likely, that is ruled out.
Any other thoughts?
My fish are already dead so I guess it doesn't really matter, but I would like to know exactly what happened..
 

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Yeah the water treatment here will tend to get more ammonia (1-2ppm) in the spring. Only by the oceanfront is what I noticed. Sorry for your losses. I have never kept discus because they seem like way too much work for my area due to ph out the tap and R/O is a long drive to go get.
 

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Test your tap water again, pH and get yourself something to test KH, GH as well if you can.
I'm guessing your KH is super low.
Leave some tap water in a container overnight and test pH over the next couple of days.
 

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I can't say what caused your pH to crash, but I'm guessing it's related to the cause of death for your fish.

To clarify- ammonia and nitrites are toxic and are at zero concentration in a healthy aquarium. Nitrates are expected, and should read at least 5 ppm in any non-planted aquarium. In my tanks, nitrate hovers between 10-20 ppm, and I know I've gotten behind on my water changes when it gets to 20 or more.

The most common acidifying substance in aquaria is organic matter from decaying poo and food. The pKa (a measure of how acidifying a compound is) for dissolved organic matter (DOM) varies, but it's considered a weak acid. If there was no buffering capacity, a large input of DOM could drop the pH to 5, easily.

Did you stir the substrate a lot during your last water change? Has it been a long time since you vacuumed the substrate? When was the last time you had a normal pH measurement in the tank?

Unfortunately, we can do all this sleuthing, and still not know for sure what killed your fish. I'm sorry for your losses, and I hope we can get it figured out.
 

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Discussion Starter · #11 ·
I have been testing the water.
pH straight out of the tap is around 9.
pH of tap water after sitting 3 days in a bowl is around 7.
pH of tap water after sitting a week in a bowl is still around 7.
The fact that the pH dropped like this.. Is this normal?
KH straight out of the tap is 3dKH.
KH out of the aquarium is 1dKH. >What does this mean?
I don't have the means to test GH yet.

As for the dissolved organic matter theory - I have no substrate in my aquarium for that very reason. I have had trouble in the past keeping my water clean when I have substrate. The bottom of the tank was always nearly spotless. The bottom feeders could easily find all the residual food and poo.
The last time I had a normal pH measurement - Good question. I never had to measure it before because my water changes were frequent, and the fish never showed any symptoms that would push me to test it.

As for what the city water facility told me:
-The city's water is normally between a pH of 9.2-9.4.
-The Hardness of the water does change throughout the year but not in response to melt down.
-Total Hardness(GH) as CaCO3 ranges from 24mg/L to 47mg/L and the calcium Hardness (KH) as CaCO3 ranges from 17 mg/L to 35 mg/L. Our plant does not adjust the process for these changes.
-The changes do not happen with run-off and usually happen with the temperature of the water. ie getting softer in the summer months when the water is warmer and therefore more limestone is dissolving in the water.
-We often get a spike in our alkalinity during Spring run-off events but looking at our data we haven’t seen a change as of yet even with all the melting.

It seems to be leaning towards alkalinity, but I'm not overly convinced based on what the city told me.
 

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It sounds like your tap water is similar in mine- high pH and zero buffering capacity. Municipalities often add NaOH, a strong base, to raise pH to avoid dissolving the lead in pipes. However, with no buffering, and degassing of CO2 when exposed to the atmosphere, the pH will plummet.

My best guess to how we got from pH 7 to 5 is still DOC, since we know that it is present in an aquarium and can lower pH. With no substrate though, I would guess that your tank pH has been at ~5 for awhile. You don't have peat in the filter, do you?

The long term fix for you is likely not baking soda- which will bring pH to 8.2 For circumneutral ranges, phosphate buffers are common. That's a little harder to do at home, so you'll probably end up buying a discus buffer.

pH itself is a proxy measurement. Different compounds dissolve and precipitate depending on pH, and fish have evolved their gill and osmoregulatory functions to particular pH ranges. So pH isn't a direct cause of death, but can weaken the fish and effect organ function. In this case, it may have been an accumulative effect of pH stress combined with disease.

Did you lose all the fish in the tank? If so, empty and sterilize it (bleach works) before adding new stock. Rinse everything really well several times, and then use a good dose of dechlorinator when refilling. I don't mean to be insensitive, but your tap water chemistry would be very easy to adjust for hardwater species, if you decide to try something else when you restock.
 

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brian226 said:
could it be columaris?
Possibly, but the reason the fish got sick is linked to water quality (lowered immune response due to stress). Since snails are not hosts for many diseases that can transfer to fish, we don't really have a source for new contagions. Unless- when you bought the snails, did you dump in the bag water as well?
 
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