Bassersdorf Novice ask for help! Would you please help me see if the koi is congested?

Bassersdorf Pure novice rookie, the fish was bought home and put in the fish pond for a week and two were killed in battle. I was tired to ask for help.The newly built fish pond has about 60 square meters of water, and the purification system has been done. Last week, I bought the first batch of fish, killed insects and sterilized them before putting them down, and put 150 kilograms of salt.About 5 days ago, it was found that the white part of a red and white koi was congested and powdered. Then the next day it was found that the fish had been swimming near the surface of the water, its head sticking out while breathing and swimming. It won't work if you look at this fish on the third day. (for the video, please see the next article)Originally thought that this fish may not adapt, but then another fish appeared the same situation, this morning seems to be dying, the fish out of the pond is like this in the picture below. Then there was a red and white part of the pool that began to turn red. At present, except for red and white varieties, there is no problem for the time being.Ask God to help me see what's going on?
Bassersdorf Brother Tianmen commented: I fish pond, fish tank, never dead fish. Your pond is definitely not so easy to die fish, the big one can be called a pond. Change the water again, put one kilogram of salt in each side of the water (flake, 200 tablets), nothing else, absolutely no dead fish.
Bassersdorf Brother Tianmen Diguizi commented: salt should be in the shape of a tablet, the kind that costs 80 yuan for ten jin, what kind of insecticidal and germicidal medicine should be put in the new pool, nothing, one kilogram of salt should be put in each side of the water. Fish farming, if you don't take fish seriously, you can live, the more you toss, the faster you die. (the main reason for putting salt is waterproof mildew)
Comments on turning gas into demons: it's obviously a stress reaction.
331915888 comment: I come to study
0 continuous self-improvement 0 comment: the buttocks are red and may be enteritis
Honey stomp comment: three more were killed today.
Only 1.8/1000 of the salt was tested yesterday. Try adding some salt today. I hope it works! Please also give us some valuable advice.
Honey stomp comments:

Doesn't anyone know what to do? Rivers and lakes are in an emergency.
