60 Gallon Tank Mystery illness killing everyone


What is the water volume of the tank? 60gal
How long has the tank been running? 11 months
Does it have a filter? Yes (biomax and small bag of crushed coral)
Does it have a heater? Yes
What is the water temperature? 74-76
What is the entire stocking of this tank?
5 cherry barbs
8 Neon tetras
2 long fin tiger barbs
1 mystery snail
7 bronze cory cat
1 kuhli loache
4 otocinclus

How often do you change the water? 2-3 weeks pretty much when plants and water lettuce gets out of control
How much of the water do you change? However much it takes to get my floor clean, generally about 10-15%
What do you use to treat your water? Water conditioner (water has no chlorine, but I’m paranoid)
Do you vacuum the substrate or just the water? Substrate only

*Parameters - Very Important
Did you cycle your tank before adding fish? Yes
What do you use to test the water? Mix of test strips and API liquid tests (Gh,Kh, Ammonia)
What are your parameters?
Ammonia: 0
Nitrite: 0
Nitrate: 0
pH: 7.3
Gh: 6 degrees
Kh: 4 degrees

I bought a completely different brand test kit and retested because I thought for sure something had to be wrong here

How often do you feed your fish? Once a day
How much do you feed your fish? Whatever they can eat in about 2 to 3 minutes
What brand of food do you feed your fish? Hikari, tetramin, api
Do you feed frozen or freeze-dried foods?
Dried only

Illness & Symptoms
How long have you had this fish? Various lengths of time, most for well over 6 months

How long ago did you first notice these
symptoms? Few months ago, just got worse in the last week

In a few words, can you explain the symptoms? For a few months ive been having a fish die here and there. At first I chalked it up to they are old fish that do not really live all that long, but this last week or so has gotten outta control. All breeds of my fish are dying with no symptoms except from my loaches. I watched two of them zoom around the bottom of the tank abruptly stop, sit on the substrate for a moment, flail all around appear to struggle and gasp, then abruptly die. In the last few months I’ve lost a handful of otos, a Cory cat, mystery snail, cherry barb, 3 loaches, a few Pygmy Cory cats. Everyone is fine swimming around and eating, and then the next day I come home from work and find someone dead. Help me?

Have you started any treatment for the illness? No
Was your fish physically ill or injured upon purchase? No
How has its behavior and appearance changed, if at all?No


If you are doing water changes every 2-3 weeks, i think you would have better luck either changing the same amount every week or changing a bigger amount every 2-3 weeks, like closer to 50%.
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I can give it a try! I’m just not sure why everything is abruptly dying if nothing is parameter wise or visually off
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It sounds like you have "old tank syndrome." Basically, this means that most of the trace minerals in your tank have been depleted and there aren't enough water changes to replenish them. I would highly recommend you do a tank flush as described in this link:

Once you replenish depleted minerals, I suspect your fish will start to do much better! And please keep up with weekly water changes of about 25% to prevent this from happening again.

Hope this helps and please feel free to ask any additional questions you may have!
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As that link says, I don’t think it would be a bad idea to be doing my once or twice a year anyhow. Thanks for the info!

I do have some more questions actually. I would love to look into all of this further and get some more info. Do you happen to know what minerals are depleted? I have an absolutely ton of plants that grow pretty darn quick, is it possible their uptake of minerals is more than what would normally be turned over leaving little for the rest of the tank to operate on? Would something need to be supplemented?
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One of the primary things that happens with old tank syndrome, is that buffers in the tank get used up. Carbonate and bicarbonate are important in stabilizing pH, so when they get depleted, the pH can start to drop. Other trace elements that get depleted include calcium, iron, magnesium, sodium, manganese and more. All of these are crucial in proper osmoregulation, immune function, enzymatic function, muscle function, chemoregulation and so much more. Fish become much more susceptible to disease when they have a deficiency in trace elements, and their bodies simply don't work the same. Sudden and unexpected death of fish for seemingly no apparent reason is a telltale sign of old tank syndrome. I haven't heard of plants taking in so many micronutrients that the fish start to suffer, but it may be wise to increase water changes anyways, to replenish lost minerals. You could also consider getting fertilizer for your plants to supplement trace elements they normally take in from the water.
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Just the response I’m looking for! Thank you so much!
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So glad to help! I'm always here to answer any questions you may have!
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Are you on city water? Sometime cities like to load their water in the spring with chloramine. This will kill your bottom dwellers first if the water that goes in is cooler than the tank. If you water conditioner takes care of chloramine as well as chlorine this is probably not your issue. City water can be fine for years until someone says "Hey, we can save money with chloramine!"

I'm guessing you are running 0s because the water lettuce is eating all the nitrates.

I do not think you have "old tank syndrome". Your tank is 11 months old and you have a sack of coral in your filter. The coral is leaching minerals into the water. I'm guessing your tap PH is lower than your tank PH?
Also 2-3 weeks for 10-15% of your tank should have it plenty recovered due to feeding by the next change.
I have never personally encountered a tank with old tank syndrome, though I have heard tales of people tearing tanks down and throwing away everything old to fix the issue.

Now if you are only changing the water with RO without remineralization, you can have issues. Your PH looks too high for me to guess this is the case. For this to be the case I'd expect bigger changes that are far more regular.
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So funny story I actually switched water conditioners about the time this started. The new one claims to take care of cholramine but who knows how true that really is. I am on city water, I called around ( bout 10 calls) and my city and county refused to answer about chloramine and the water reports are years old.... so that’s odd to say the least.

I think you’re on to something though. I really wasn’t so sure about OTS since my plants are so healthy and I’m having fish successfully reproduce... but I was willing to grab onto anything to try to explain this. I’ll have to grab some of the other brand of conditioner and see if that’s the secret sauce, and may have to see about a FOIA request to my city.
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