German discus

I got 4 new German discus, I have one that will not eat. I’ve tried almost everything. Please help. I don’t want it to die.

Try raising the water temperature to 90 degree Fahrenheit.
Higher temperatures also increase the fish's metabolism and appetite.

Hm, interesting. This is the first I have heard of it.

I agree w Francis...how long have you had the discus? How many days since it last ate anything?
Hexatemia is a common pathogen present in all aquatic environments and in fishes gut...when fish get stressed from shipping, relocation, bullying, etc, the immune system can depress and the hex parasite load increases causing fish to lose appetite and stop eating, eventually will have white stringy poop...90 degrees will not only increase metabolism and appetite, it will also disrupt the life cycle of the hex parasite...if you notice stringy white poop or the higher temp alone does not cause your discus to eat then then you can assume it's hex infestation and need to add metronidazole at 400mg/10 gallons daily for 8-10 days with a 50% daily water change before redosing each time.

I assume by German discus you're referring to Stendkers? If so, that's a fairly common occurrence for me. The Flachens I got from Hans took 5 - 7 days before they started eating regularly. Two weeks later, they eat like refugees.