Silver Shark with discolouration

[monterey girl]

Hi

We have new 3 silver sharks in our tank, we received them on Sunday.

At first the 3 of them swam together then one of them is often by itself. Is with the others in the mornings.

Have noticed it has discolouration of its body (a white patch, not bubbles like white spot) and a lot of the time it is sitting at the bottom of the tank.

The water was tested at the aquarium shop where we got the fish on Tuesday and it was fine.

Any suggestions as what is wrong with it. We are new to the fish world.

I have a picture but not sure how to upload.

 

[Thyra]

Welcome to the forum! Are there other fish in the aquarium and what size is it? Also anytime you get the water tested you want actual numbers - not just "fine". Many LFS don't understand this. Do you know about cycling?? Your goal is Ammonia and nitrite zero and nitrate about 20ppm. Buying your own liquid test kit is important. API is highly recommended by most members.