Don't run really high concentrated chlorine through your pumps, it might damage them. I would scrub with the high concentrate then siphon or bail out the water then run the pumps with a milder solution to make sure you get all the virus or whatever killed your Koi. then get some feeders to re establish your bio system.
You have to sterilize everything or it may come back to haunt you. This includes nets, hoses, air lines, airstones, sponges used for cleaning, everything.
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments. After that, you can post your question and our members will help you out.