Make sure there is no ammonia, nitrite or nitrate in the aquarium water, and make sure the pH is similar to whatever the water is where they came from.
Increase aeration/ surface turbulence to maximise oxygen levels.
Photograph the fish and send an email with pictures to the supplier.
Turn the tank lights off for today and see how the fish look tomorrow.
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TURNING LIGHTS ON AND OFF
Stress from tank lights coming on when the room is dark can be an issue. Fish don't have eyelids and don't tolerate going from complete dark to bright light (or vice versa) instantly.
In the morning open the curtains or turn the room light on at least 30 minutes (or more) before turning the tank light on. This will reduce the stress on the fish and they won't go from a dark tank to a bright tank instantly.
At night turn the room light on and then turn the tank light off. Wait at least 30 minutes (or more) before turning the room light out. This allows the fish to settle down for the night instead of going from a brightly lit tank to complete darkness instantly.
Try to have the lights on at the same time each day. Use a timer if possible.
If the light unit is programmable, have it on a low setting for the first 30-60 minutes and increase the brightness over time. Do the opposite in the evening and gradually reduce the light for the last 30-60 minutes before lights out.
If you don't have live plants in the tank, you only need the light on for a few hours in the evening. You might turn them on at 4 or 5pm and off at 9pm.
If you do have live plants in the tank, you can have the lights on for 8-16 hours a day but the fish and plants need 8 hours of darkness to rest. Most people with live plants in their aquarium will have the lights on for 8-12 hours a day.
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The following link has information on wild discus and is worth a read if you want long term success with the fish.
Dec 22, 2008 - of the lake hosting more than a thousand discus. Only 16 of the 41 ..... ing free-swimming B. cichlae wit...
m.moam.info