Water Levels Gone Crazy. Please Help (:

[ninjacheesefish]

So, I've come home to 5 dead fish. I went into panic mode and did a 80% water change. I did a water test and the levels are soooo high. How did this happen??
Other details below:

Tank size: 80 liters
ammonia: 4ppm
nitrite: +5ppm
nitrate: 80ppm

How did they get so high? The tank was set up in April, and has been going since then. No recent addition of fish, added pimafix last night to treat a molly. Weekly water changes done (20%), on sunday the water was within good levels (Ammonia 0ppm, nitrate 20ppm, nitrite 0ppm).

The dead fish so far:
- Harvey the Panda Garra
- Madame Dropsy the Columbian Tetra (she had dropsy)
- Travis the Columbian Tetra
- Cashew the Columbian Tetra
- Texas the Blind Cave fish
- Ohio the Blind Cave fish

RIP darlings.

 

[thereverendturtle]

Did someone possibly over feed your fish while you weren't around?