Life Expectancy

[LookoutTrout]

In the last year about half of my fish have died for no apparent reason, no obvious signs of disease or cycle issues. They are all standard small community fish - Guppy-Platty hybrids, Panda Cory, Black Skirt/Widow Tetras, Indian Glass Fish, Nerite snail.
They have been dropping individually, no mass extinction event and no one species wiped out.
9 out 10 glass fish are gone, 2 out of 5 Platty things, 1 out of 6 snails, 5 out of 8 Tetras (I got 4 of them about 3 years ago that had no issues in a nano tank) and 2 out of 5 Panda Cory.
I had a problem with old tank syndrome when I lost a new SAE and a Bamboo shrimp, that was when I found my 25% weekly water changes weren't enough so I've been doing 50% since then and cut feeding to every other day.
My remaining SAE will go glass surfing at the drop of a hat and it seems relaxed most of the time, just occasionally upset during water changes.
What is a normal(ish) mortality rate and is there something I maybe haven't considered that could have changed in my water?

[BigBen]

Is it possible you lost a fish and not known about it? That could quickly foul the water.

The life expectancy varies in your fish. Cory's can get 15 years, whereas as live bearers are often a little weak from over/in breeding unfortunately.

[Gingerlove05]

Guppies 2-3 years, maybe 4 at a push. Platys are around 3-4years.
Tetras can vary, and Indian Glass fish are known for being sensitive.
I would say with the mix of fish you could be looking at a hard water/soft water species issue or soft water/hard water species issue. Especially over the longterm this can cause more issues.

[black ghost]

I’d say about 4-5 years on average for fish this size.

What were the parameters, eg pH and nitrates, when you were doing 25%?

[LookoutTrout]

Nitrates went off the chart before, it took several 50% changes to see any change in the test kit colour. Since that happened about 8 months ago it has been between 0 and 30 depending on how the plants are growing.
Nitrates are currently about 20 which is what the water company say the supply is, no surprise as I did a water change at the weekend.

PH is consistently 7.6 from the tap and 7.2-7.6 in the tank.
dKH is 3-4 from the tap, this has reduced over time in the tank and has been 2 for the last couple of weeks though I don't check often.
dGH is 7 from the tap and 9 in the tank.

My PH test only goes up to 7.6, I'm wondering if it's higher than that.

[black ghost]

The nitrates were probably the cause of the deaths. Exhaustive studies are yet to be done for nitrate toxicity in ‘aquarium fish’ species, but the growing consensus is that nitrates should be kept below 50 for the more ‘nitrate-tolerant’ species, and 20 for less tolerant species such as cichlids.
High nitrates cause chronic stress (it’s not clear yet whether it’s actually the nitrates that are the problem or the other things that accumulate with it). Chronic stress can cause all manner of issues, some of which are not seen, but a shortening of lifespan can be expected, often with no obvious symptoms.

[LookoutTrout]

Guppies 2-3 years, maybe 4 at a push. Platys are around 3-4years.
Tetras can vary, and Indian Glass fish are known for being sensitive.
I would say with the mix of fish you could be looking at a hard water/soft water species issue or soft water/hard water species issue. Especially over the longterm this can cause more issues.

I discovered the livebearers weren't a great idea after the LFS at the end of my road told me local water was absolutely fine for them. To be fair to him they seem to have coped just as well as the others but I have learnt I should always take his advice with a big pinch of salt.

I think the Indian Glass fish went in after I'd corrected the nitrate problem but they were very small and it could just be they are fragile.
I'll chalk it up to the nitrate issue and think carefully about restocking, I feel some cherry shrimp coming on whilst there aren't too many hungry mouths in there.