3 1/2 year old orandas suddenly dying

[Andalons]

I have/had 5 Orandas in a 75gal with a PennPlex canister and a 75 gal hob
I suffered the usual screw ups in the early days about 5-6 years ago. But after extensive reading feel I have a pretty good grip on things. For the last 3 1/2 years I have had the same 5 Orandas with no issues.
I do regular water changes, I test my water.
My parameters are always good. Suddenly without any sign of illness.
My fish are dying. Help?

 

[Aiken Drum]

Can you give some more information? There isnt anything there that gives any clue as to why your fish are dying. With no symptoms its very difficult to make any kind diagnosis and all anyone can do is guess what might be the cause.

How many of your 5 fish have died? Did they die at the same time or did they die over a period of time?

How big where your fish? Have they always been in the 75g?

Can you confirm your water parameters? Actual numbers, not just "they are good"?

What is your usual water change schedule? How much? How often? When did you last do this?

Have you changed anything from your usual routine? A different dechlorinator? Different food? Or anything new gone in the tank? Or some new equipment?

Might something have got in the tank? Soap, perfume, hand sanitiser? Might you have forgotten to use dechlorinator? Might your water company have done something unusual to your water supply? Like chemically clean out the pipes and you then did a water change?

 

[Andalons]

3 1/2 old orandas dying help

Im going to give you the answers to all your questions. I just didn’t want to ramble at 1st.
2 of my 5 have now died. The 1st died about 2weeks ago and the 2nd earlier today.
My fish are about 5” including tails. ( One is only about 3 inches he is the offspring of the others)
They were in a 55 gal until last year when I upgraded to a 75gal.
Water parameters- pH 7.6, Ammonia 0.0, Nitrite 0.0, Nitrate 5.0-10.0
Water changes are once a week, usually about 30-35%. I am not perfect i may go a few days beyond here and there but I do try to stick to once a week.
I have well water on my property. I have lived here for 8 years. I have always used my water from the tap and added Seachem Prime and Seachem Stability.
I do have 3 Nerites snails just to mention. I have had them in there almost as long as I have had the fish. There have been no new additions to the tank including no plants, critters, decorations.
It’s has been a awhile since I opened my filters to clean out but not super long.
I feed Repashy Super Gold gel. Omega one goldfish pellets in a pinch. And the occasional peas or spinach
I can’t think of anything. Other than doing some bottom sitting for a few days before they are not exhibiting any signs of anything. For all outward appearances they look healthy. No buggy eyes, no ratty tails, no white spots or any kind of spots, their bodies are smooth are free of any blemishes. They are not bloated looking. They are not swimming erratically or scratching on things.
I have some brown algae right now that has creeped up unexpectedly. We did disconnect a water softener last summer and our water started tasting different.
I just don’t know. I am planning on taking my water to be analyzed ASAP. Any guesses in the mean time?

 

[Aiken Drum]

There is nothing obvious that leaps out as a cause of death.

Could be an internal parasite that isnt causing any visible signs of infection until the fish dies. Could be a genetic thing and you just got unlucky that it effected 2 fish in a short space of time. Sometimes fish just die.

Im not really sure that analysing your water will achieve much unless you have done this regularly in the past and have something to compare your new analysis with. It may throw up something though.

Unless you plan to start randomly trying treatments for what may be healthy fish im not sure what else you can do except keep an eye on things. Consult with a vet? Have an autopsy undertaken? Completely break down everything and start over? Install an RO filter?