Cory's are swimming strange and get distorted

[Geppy]

Hi,

I got lucky and on 29 october my cory's (aeneus) laid over 570 eggs.
I managed to keep over 460 alive.
After a month I saw that my nitrate level was way too high.
I correted the situation but noticed that some were starting to swim in half circles and a bit upside down.
Also they got a bit darker at the start of the tail and some got distortions. Tail in an angle of 80 degrees compared to their body or and S shape from head to tail.
till now none were cured and they slowely die.
Now my water is fine and I gave them an eSHa 2000 + Exit treatement. But I still notice new cases.
Already 200 were given to a club and they are now around 1 inch big.

Does anyone know what is wrong and how I can correct this situation?

Thanks a lot for any valuable advice.
Geppy

[Silurus]

The high nitrate levels the eggs were exposed to were teratogenic (i.e. caused developmental abnormalities). There's not much you can do except to start over and watch the nitrate levels this time.

[Geppy]

Wow,

This is a speedy reply.
Thanks a lot already for the info.
At the moment I get around 15 new eggs once a week.
So this is looking good.
Now for the others, is it normal that these symptons occur even only a month later, when things are back to normal.
Will they all get this?
Note as well that the nitrate level only became too high after 3 weeks. They were in a seperate tank with only an air filter. I think the problem was that I changed the water too often and got 'dead' water.
I removed to the big tanks with an external filter. and the nitrate stays well under control here.

Geppy

[Silurus]

Are you monitoring your nitrite levels also? Nitrite is also teratogenic.