Newbie needs help

[joe1225us]

Had two Discus in a 110 tank. Only fish there. One just died. Turned black and died. No visible symptoms other than than clamping and turning blackish. Happened quickly. Second, which was looking fine is still looking fine most of the time. Swims around looking fine. Then will suddenly dart about frantically. And will then sulk in the corner for a little. And then will swim around looking regular. No visible signs of anything. What can it be, and what should I do.

[two utes]

It could be a number of things Joe, but the first thing that i would suggest is keeping a larger number of discus in your tank than 2

[captainandy]

try switching out your heater

[fljones3]

As Joe said, it could be anything. Discus are schooling fish. At 10g per fish, if its a 110 gallon (not 110 liters) you would want something around 12 adult discus.

[joe1225us]

try switching out your heater

Do you mind explaining that? Because I have an expensive one, with a digital controller. temperature is an even 84

[Iminit]

May be the heater has a grounding problem. Do you ground your tank? Also as said these fish are schooling fish. So by being alone it’s stressed and looking for another. May be time to visit discus madness .