i have 6 oscar and have had my share of problems ....i would do some water changes like 20% at a time 3 times a week and add a tblspn of salt per 10 g of water,.....also turn the temp up to about 82-84f....good luck this has worked for me
im no pro but ive tried this with my boys even cure hthd after time.......
have fun with your friend