Okay, so in August I put plants in the greenhouse AP system and they have been growing like crazy. About 2-3 weeks later I introduced some Tilapia that I had in the garage (6-12") and for the last two months things were going fantastic. About six weeks after the Tilapia were put in, I introduced some trapped Bluegill fry and a few gold fish into the other fish tank (330 gall ibc totes). My thought was to have one tank for bluegill and catfish, and one tank for tilapia (seasonal). Both tanks are on a common system with 2 ibc totes buried in the ground as sumps with 300 gallons worth of media filled grow beds and 300 gallons worth of raft tank. Still everything went fine. About 3 weeks ago, I bought 60 4-6" channel cats from a hatchery and I was so excited. Up till this point every thing had been going great with no fish deaths at all. The fish were delivered on Friday and that weekend I installed two auto feeders. Within a few days I noticed a few catfish died (2-3 daily). Then all of a sudden gross amounts of fish died daily both catfish and Mature Tilapia for about 3 days till they were almost all gone. The fish turned whitish in color and seemed like they may have been bleeding from their gills. The gills were a grayish color. While netting dead fish I noticed excess feed on the bottom of the tanks that had a clear gelatinous coating around it. I cleaned the tanks and did a half water change for the system, added Ich medicine and still the fish continued to die. After the fish died off, I let the system keep running for a couple of days and tried reintroducing comet gold fish. Within a week they were all gone. I am new at this, but I am learning. How can I nail down the cause of death? I tested the water and nitrites, nitrates, and ammonia were within normal range. PH was 8.0. I can attribute overfeeding to some cause of death, I used an herbal anti fungal spray on some cucumbers (pet safe), and the catfish may have had a disease coming into the system. Any thoughts?

With thriving plants in my system, how can I kill or eliminate what is killing the fish? Do I need to do a complete water change and scrub the tanks and filter barrels (radical flow flowing into a vortex)? What will clorox (chlorine) do to the plants?

Any input will be appreciated. I still have blue nile and golden brood stock in my garage to start again this winter. Thanks for listening.
Tom