Need help with Koi please

[sissy]

do you have an aerator hooked up to the stock tank Like Dave said they need the air in the water and get a liquid test kit .I think most of us use API .For a filter in my stock tank I use a small container with my pump inside it with lava rock around the pump in the container .If you don't have anything this will work for a quick fix .I use it all the time in my stock tanks and just pull it out hose it off and put it back in .