oscar fish with white slime killing them

Question
hi tina was just wondering if u could help me with a fish tank problem i have just set up a tropical tank for oscars i put new gravel in hav 2 under gravel filters and one canister filter. i waited 2 to 3 weeks after starting got ph level checked at a aquarium shop in my area the man said was ok to start putting fish. so i put 2 oscars in the the tank they were fine 4 the first 3 months but just a few days ago they got the white slime on them and died have u any idea what would cause this to happen. i do a water change every 3 weeks we use filterd water from our special tap for this .regards SHANE MC DONALD

Answer
Shane,   When you have two cichlids that wat meat like them your new tank really should've been cycled out with a live bacteria for at leasr 6 weeks. This would have you gotten past the new tank sydrome. When a tank cycles down it of couse has a bacteria bloom and you get the foggy eater but it settles. Thne you get your high ammonia levels This bacteria is what keeps your tank clean, your undergravel is a form of biological filtration to speed yp this process.Your canisters are mechanical filtration and should be perfect for you tank. Then your bacteria reprocesses the water turns your ammonia to nitrites....then again to nitrates. You should have used cycle a live bacteria ot put a cuoule feeder goldfish they prob would have eaten later in there to get this process out of the way. Without adding the bacteria or the bacteria from the wastes of the fish I can't even imagine cycling down a large tank. So, what I think was something was getting high numbers I believe it was probably you ammonia level was to high it ate their slime coats and sets just say stressed them to death,,,,,,,,I am sorry you lost you babies , cycle tank out with a couple fish in there or live bacteria and you should avoid this happening again.....Good Luck , Tina