I am have removed all other fishes except the loacH. Yesterday I did a complete 90% water change and removed the gravels and other stuff from the tan. Today also I have done 25% water change with adding meds and some salt in the tank...I was more going for the heavy bioload on that tank. That is a lot of bigger fish in a small tank. In addition to separating the fish I would monitor water conditions closely. I imagine nitrates are fairly high unless water changes are being done daily. An injured fish with less than pristine water parameters can lead to other issues.
I seriously want it to survive. It keeps swimming in the tank but keeps spinning it's body upside down at times, then goes down to a place and sits for a while. Sometimei see it upside down at the bottom and then again hegeyd staying and will swim a little