Almost over night some thing happened to water. After work I checked on fishes, at first I though they where all gone. I got a flashlight and did find 2 that have white markings. I placed a fence panel over top of pond in case it was a predator. Panel was not moved during the night, if fish died would their bodies float ? Can a handful of a rotted plant turn 300 gallons murky ? I ordered a hornwort from ebay when I opened package it smelled really bad, not knowing what hornwort smelled like I put it in pond. I do not have a filter, but one is coming. Should I wait till filter comes empty pond, hope fish still alive and start over?