need a bit of advice please

[mitcore]

my 3ft com tank has gone bad
i have doen water testing and here are the results
nitrates - 20ppm
nitrites - 0.0
ammonia - 0.0
and ph - 7.0 ( good for this tank)

but i had 3 dead today and 2 that were that sick they had to do the dunny run, yes and i hated doing it too

i have no idea whats up with the tank, my bristle noses are still breeding and none of the 150 fry are dead, but yet i am losing fish

any ideas
would be awesome thanks all

 

[neilanh]

have you done anything recently to the tank? New filter media, water changes, etc? Check the temperature in the tank, has it shifted significantly?

 

[mitcore]

nope absolutely nothing,
the tank hasnt had anything added to it nor have i changed any cleaning