I have aquired water test strips this past week and the nitrate level was extremely high. The ammonia and nitrite levels were safe at best. The alkalinity was very low, and ph was lower than strip indicated(acidic). The past 4 days, I treated with 2 doses of "General Cure" containing Metronidazole. recommended for the "Hole in Head" disease. This cleared up the ick on his side mostly. Today I removed about 15 gallons, and replaced with 10 gallons (which I had at room temp) . And will add the 5 more gallons tomorrow, keeping temperature consistent. I previously only changed water every few months, but have learned that needs to be about monthly. I use a double carbon filter, I believe rated a little higher than needed, and have lately been adding additional "Ammo/Carb" to filter which seems to be helping with Ammonia. I will check water and change again shortly to try and bring nitrates down, and ph up. I also added 2 Tbsp of salt when water was added today.
Larger tank at this time is not practical, but trying to bring him back to healthy. He hasn't eaten last few days, but am going to try something other than pellets, that I usually feed.
Thanks for feedback
HITH/LLE is generally caused by poor water conditions. Using medications like metro won't stop the HITH if the water conditions are not improved. If you want to bring him back healthy, get a water changer and start doing 50-75% water changes everyday for the next 3 months. Clean water will heal over 90% cases of HITH.