Dead Cory

[IcQb]

So yesterday evening one of my trilineatus cory's snuffed it...

Over the last two years i've kept those fish in a well established, well planted tank with Neons and otto's.
neons have tetra disease (boooh!) and the otto's are fat and healthy.

I've bought 5 tris 2 years ago. 3 snuffed it in the months afterwards.
THen i got the two survivors 4 new friends. Again those four snuffed it in the next months.
2 months ago i bought them 4 new playmates. Guess what. Two died a few days after transport, and one snuffed it just yesterday.

I saw it swimming happily across my tank, went to watch some tv and when i came back a few hours later it was lying on it's side barely 'breathing'...

Water values are all right. I use RO water mixed with tap water (4-1) to get soft water and use a little black water extract to get that nice amazone feel.
I feed them the normal granular food, some wafers for the otto's and live food every week (or more) (artemia, blackworm, bloodworm, mosquito larvae, etc...)


Does anyone have some clues as to why my established corys seem to snuff it for no apparent reason and only the two old ones survive?

 

[N0body Of The Goat]

Could a shortened lifespan through heightened metabolism be a factor? Corydoras trilineatus are sub-tropical just like C, paleatus [Peppered] (they have been recorded in 16C water) , unlike the tropical and similar C. julii.

 

[IcQb]

I'm fairly certain that could be so!

But it does not explain why the two oldest ones still swim around and it's the new ones that snuff it.
In the LFS they do alright in the same watertemp for ages

 

[N0body Of The Goat]

All I'm saying is that if they have been kept permenantly at >20C, it will shorten their lifespan, just like other sub-tropical fish like Redline Torpedo Barbs. If the LFS kept them at say 25C too, that does not make it right.

Another possibility is that your RO/tap water mixing is a factor, lowering the kH and gH (and pH) of the water too quickly for the newcomers.

 

[Inchworm]

I have no idea if Old Tank Syndrome is a possibility for you, but whenever I hear of new fish dying and old ones living, I suggest that it might be something to consider. Check out this explanation:

http/www.bestfish.com/oldtank.html

 

[IcQb]

That all makes sense, never new there was a 'term' for it.

But I don't thinkt that's my problem.

I clean the sponge of my filtre every 2 weeks (there's citrax in there to hold bacteria).

New water is added and changed bi-weekly (it's heavily planted)
Tropol is added for some blackwater-goodness.

And the plants receive a dose of ferts regularly.

I'm very busy with this aquarium as i wanted to cory's to mate. (remove some water, put in fridge, add to aquarium).

Water values have ever been constant (ph = 6,5; KH = 3, GH = 12, no NO2, NO3 or NH4...)
(KH is prob. a little higher, but tank has bogwood and many plants)...