Need Help - Discus turned dark

Hello, I have the "boss" (dominant fish) of my tank - a solid turquoise in color discus - turned dark a couple of months ago.
I have in total 4 discus now. 2 of them formed a pair around the time that the symptoms of the darkened discus (boss) started and the male used to fight a lot with the boss so I separeted the pair and the other two 20 days ago in the same tank. During that time and until now the same discus has fin rot that comes and goes but i still haven't managed to get rid of it. He was eating relatively well and comes in front of the tank when he sees me but a couple of days ago started not to be able to eat as he tries to nip the food but he "misses" or when sometimes that manages to take a bite he spits it most of the time. I am afraid he is becoming more and more thin, his color sometimes gets better (less dark) but he used to be a solid turquoise.

He already took a bath a week ago in methylene blue due to fin rot with little improvent but it shocked him more


Tank size: 400 lt (120x80x80 cm)and 70 lt sump, I have the fish around 8 months now but the sick boss fish was from a previous "batch" of discus that I bought a year ago.

Is anything I can do to help him regain his health and color? I am afraid he will stop eating at all and eventually die. Thank you in advance for your help!


5. Water changes: 50% once a week - I am afraid due to family and job this is the best I can do for now...


6. The tank is running for 12 months and is bare bottomed with a big wood and two small anubias


7. Do you age your water? If you do for how long and what is the ph swing: I used to use tap water but after fin rot i switched to RO water (gradually) and now i only use 100% RO water during WCs aged in a barel for around 2 days. Only the automatic top up uses tap water declorinated and aged in a smaller barell. Unfortunatelly Ph is still around 8 (as tap water) with KH 3 and GH 2


8. What type/brand water conditioner do you use? Prime in the top up barel for the total capacity of the container


9. Parameters and water source;

- temp 30oC

- ph 8

- ammonia reading 0

- nitrite reading 0.05

- nitrate reading 5

10. Any new fish, plants or inverts added recently. NO


11. Please tell us what you feed your fish and how often. 3-4 times a day a variety of comercially available foods (pellets, flakes) such as: Tropical D-50 PLUS flakes, sera ImmunPro, Tetra Discus and Prodac Bloodworms chironomus) usually dipped in Seachem Discus Trace

PS: The second foto is one month ago, he had already started turning grey-ish and the first one is today (very dark-colored)
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Everytime I've ever had a discus, previously healthy and not being bullied, turn dark and not eat well - metronidazole is usually around the corner.

Quote:

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Originally Posted by captainandy

Everytime I've ever had a discus, previously healthy and not being bullied, turn dark and not eat well - metronidazole is usually around the corner.

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I guess I 'll give it a try, i will mix some in his bloodworms and i hope he'll eat them...

There's a lot in your first post I can't totally get a handle on, like your pH reading first off. Why is it 8 when you are using so much RO. It would be nice if you could fill in the questionnaire in the emergency section.

Quote:

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Originally Posted by LizStreithorst

There's a lot in your first post I can't totally get a handle on, like your pH reading first off. Why is it 8 when you are using so much RO. It would be nice if you could fill in the questionnaire in the emergency section.

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I have already filled it, it is just in the original post, I just didn't keep the format.
Concerning the PH, I had the same question and i even tested the PH of RO water today (which is 5). My guess is that GH and KH still act like buffer and keep it steady at 8 for now (as I started gradually changing tap water with RO water during WCs). Eventually I think it will drop...

Update: The discus is hardly eating the metronidazole bloodworms and sometimes he spits them out. The fin rot worsens though it has appeared now in 3-4 new spots. I don't think this is a good sign... Any treatment suggestions? Should i move him to a hospital tank or will this stress him more? Thank you guys for your help