Fish kill... what next?

[marthared]

I need to know what to do next: OK, all my fish have died over the past 4 days... angel fish, 2 gouramis, 2 pleccos, 1 catfish. Sumo loach is only one remaining. Here are stats:

36 gal fresh water aquarium
nitrates 40-80
ammonia 0
nitrite 0
ph normal

Bio Wheel filter system

About 6 days ago I washed the bio wheel, cause it wasn't turning, and this is what the local aquarium store said to do. But I washed it in chlorinated water, not thinking it would do anything. I also replace one of the 2 carbon fiber filters.
About 3 days later fish started acting sick... angel fish first, then others quickly died, with gouramis the last ones last night. Sumo loach is left. Gouramis had white spots/ich. Nitrate was 40-80 range. I did a 50% water change 2 days ago, and nitrate was still high last night. Put de-nitrate rocks in the filter box last night.

What should my next steps be? Should I go ahead and put ich treatment in the water as if there were sick fish? Do water changes every day (how much?), and just wait for the nitrate to go down. I can't start from 0 again, as I still have the loach.
Many thanks for any advice you can give!

 

[Hara]

Do water changes to bring the nitrates down and to keep any ammonia that will surely show up, in check. Do not add anything to the tank. You pretty well have killed off the biological filtration and it needs time to repopulate. Biowheels not turning is not a bad thing. The most that ever needs to be done is to swish them around in a bucket of tank water when you do water changes. Do you do water changes?

 

[neilanh]

What test kit are you using? I agree, most likely you killed off a large portion of your bacteria colony.

 

[marthared]

Yea, that's what I figured. Live and learn (or die and learn, depending on what you are!). Nitrate is still btwn 40-80. I have the API test kit.
Should I do water changes every day? 50%? Thanks so much, guys. I'll not buy any ich stuff.

 

[neilanh]

I'd do a few PWCs to get the nitrates down. Below 40 is preferred, but you're nowhere near unsafe levels, so don't panic.