Identifying why a fish doesn't eat

[Branch]

Not sure if this is the right forum for this question as it may not be a question of sickness.

Since introducing 6 2.5" discus a fortnight ago one has refused to eat whilst the others gorge themselves 4 times a day. At first I believed that it was a case of bullying but the others don't bother the fish. Even when it's not lurking in the top corner of the tank it circles the food but doesn't take any of it despite being left alone by the other discus. There is no evidence of illness, fins are down and not clamped, albeit stress bars are up, but it is so thin and almost 1/2" smaller in those two weeks than the others. Tank parameters are near perfect i.e. Ammonia 0, Nitrites 0, Nitrates <10mg/l, temp 84C, PH 6.8 (RO). Food is a mixture of dry food and discus diet which the others eat within a couple of minutes of it being put in the tank. Any ideas, I don't want it suffering indefinitely?

[jeep]

It's hard to say why they quit eating. Hex, worms, water quality, stress, etc... can affect different fish in different ways.

A good first line of defense is to raise the temp to 93 and add 2 TBS salt per 10g for 10-14 days. Recovery can take another week or two after.

If the cause is an internal parasite, the only way to be 100% sure is by examining the feces under a microscope and not just throw different meds at it, like many people do.

[Iminit]

Every time I’ve had 2.5” discus this has happened. Always 1 or 2 get left behind for no apparent reason. What I found was if I removed the laggers and added them to a qt tank with water from the main tank and slowly changed that water out over a few days most of these fish came to life and started eating and growing. When this didn’t work I would than add the salt to the qt.

[Branch]

Lagging is an understatement, the other 5 have almost doubled in size. There are no signs of stress and as I said fins are down and haven't seen any faeces so difficult to diagnose. Unfortunately I had to get rid of my QT and so, having quarantined them at a friends, who now has other fish in that tank, I'm restricted to the one tank. The fish in question isn't bullied as first thought and actively goes towards the food but doesn't appear to eat. Raising the temp will impact on the other tankmates, it is a vibrant tank.

[jwcarlson]

I had the same thing and asking here and on Simply Discus Facebook page several people said raise temp and separate. While separated my little lagger went from eating a couple bites every couple days to eating nothing. I had other issues going on and every discus ended up in QT tank with little dude. He started eating as soon as I dropped the first fish in with him. It was weird. When the main tank was cleared I moved him back over with the main pack, both tanks were at 90*. Slowly he started to eat more and he's now just about the most aggressive feeder. He's almost always the first on on the beef heart cube now. Drastic change. I'm dropping temp a degree every 4-5 days and I have down to 88 now and he's still fine. I think I'm going to stop at 86 as long as nothing changes for his eating. He's growing quickly now.

[Branch]

Interesting, I recall reading your posts and the problems you went through almost overnight.