Keyhole Cichlids

[stooshy89]

is it just me i have been keeping keyholes for just about a year now but in the past 8 months i have lost a few of them and there have been fine nothing wrong still them normal selves then next day i turn the light on to a dead one does anyone have any suggestions if i may be doing summat wrong or if the shops have some bad batches?

 

[WILDER]

Size of tank in gallons or litres.
How many fish and which type.
Water stats in ammonia, nitrite, nitrate, and ph.

Any symtoms to go on.