Ph Down, Ammonia Up !

[jimmyringo]

i added 4 cories to my tank yesterday.By this morning they were all dead.All my other fish seem fine.Anyway ,i got the water tested at the LFS and Ph is down to 6 and ammonia is sitting at 0.5.Nitrite is 0 and Nitrate is 10.

Is 50% water changes the way to go?

And what caused this?I have been a bit lax with water changes the last few weeks due to illness(been attached to heart machines after a bit of a scare ) so i've only managed two 15% changes in the last 3 weeks or so.I'll be doing a good bit of maintenance this evening.

 

[WILDER]

Need more info.
Size of tank in gallons or litres.
How many fish and which type
How long has the tank been set up
Whats your tap ph.
Any bogwood in the tank.
What substrate do you have in the tank.
.Just tell us everything you have in the tank as something altering your ph in the tank if its a big drop from tap ph.
How long did you climatise the corys for.
Corys are very sensitive fish they need matured tanks,