HLLE-Koran Angel? I've done all i can for him

[proteomicsplayer]

OK, I've read all the internet posts on HLLE and koran angels. I've been doing all the things required, which are
1) clean water- Nitrates at <15ppm (was 200ppm 4 months ago - probably cause), water changes 20% every 2 weeks now.
2) food- Mr Koran angel has been given the best diet money can buy. Live brime shrimp, flakes, formula 1, Dainichi marine, Green Marine Algae, with foods soaked in Zoe.
3) Stress- Since Korans like rocks, I've built him a rock cove. He loves it and sleeps in there and swims through it all day long. He is the boss of the tank, noone dares to mess with him and he is a good king as he rarely uses his massive size and strength against the smaller fish

Other notes:
tank 120 gallons, other fish - tang, trigger, bicolor blenny (spelling?), hawk fish, puffer. All other fish are doing perfect with bright colors.

I am currently trying the broccoli idea and he's chomping away at it, so we will see. Only other possible causes is the stray voltage theory or maybe I have to much bacteria in the water and need a UV, but that kills all bacteria, even the good so I'm shying away from adding a UV cleaner

Just so you know, I'm willing to goto the end of the world to solve this problem and may try to get him an invite into the Mandalay Bay tank in Las Vegas (which is a small ocean, although my players club needs a few more hundred points imo..)

Thoughts????

[Ninong]

Hi proteomicsplayer, welcome to Reefland!

People have reported success feeding broccoli. I would continue that plus Spirulina based flake foods soaked in vitamins.

Good luck!