thoughts on these testing parameters

[wilsonriverfish]

thoughts on these ? ive had a mass fish die off white eyes then death



[GALLERY=media, 816]IMG_1530 by wilsonriverfish posted Nov 2, 2017 at 9:02 PM[/GALLERY][GALLERY=media, 815]IMG_1531 by wilsonriverfish posted Nov 2, 2017 at 9:02 PM[/GALLERY][GALLERY=media, 814]IMG_1532 by wilsonriverfish posted Nov 2, 2017 at 9:02 PM[/GALLERY][GALLERY=media, 813]IMG_1533 by wilsonriverfish posted Nov 2, 2017 at 9:02 PM[/GALLERY]

 

[wilsonriverfish]

so basically havent had any issues in ten years which was my last post! recently has some issues pop up that have pissed me off. forst off my 12 year old raphael catfish whiskers started rotting off and his eyes turned white a day or two after i brought home a new fish. brought home a new oscar from the fish shop as well as removed the carbon and added cotton like stuff that was recommended and cleaned the foam filters after a long time.well wouldnt you know it the oscar has died about 24 hours or less when when i got it and after going in my tank his eyes turned white too. so i bought anothee mature 5" oscar from the coolest fish shop ever in Portland oregon called the wet spot.middle of the night after i turn off the lights he was periodically thrashing about the aquarium. i came home from work the next day and he was floating in his side with yup you guessed it !...white eyes ..he looked dead so i got the net and after a second or two near the net he came back to life so i went back to work. came home and he was dead and i realized i got a problem going on which is rare for me.i also have a large school of convicts that have died off recently as well.12 yesr old catfish has recovered and is doing awesome as well as the remainder of the convicts which appear happy and healthy.

backstory:
1.70 gallon
2.fluval 405 filter ( 2 trays ceramic filter media and two trays cotton like media)
3.85 degrees roughty
4.inch or two of gravel
5. 6-7 convicts amall ans one raphael catfish
6.
amonia .25
ph 6
nitrate 7.5
nitrite .25

any help to stop the fish death?