Bala (silver) shark not well

[Puffin]

Hi

We got a couple of silver sharks at the weekend. 1 is definitely not well. He's not swimming much at all, mostly sort if twitching behind the plants or filter. Sometimes he's upside down.
The other we have is fine & looks happy.
We have taken the poorly one out & put on his own as dont want to make any other fish I'll.
As we have only just got him is it acceptable to return to the shop we got him from?

 

[mfdrookie516]

What size tank do you have them in? If it's anything short of a 6' tank, I'd recommend taking them all back.

Other than that, what are your water parameters? Tankmates? Any physical signs of sickness on the one actine weird?

 

[Esoteric Backbone]

Yeah, you should be able to return it, and they will either refund you.

 

[Puffin]

All our water tests are at 0. We also have the water double checked at our lfs before getting any fish.
We are aware of the size our fish will grow & prepared for this.
At the moment we have the silver sharks in with guppies. Plants & drift wood.

The poorly fish we have isolated to treat but he doesn't look like he's going to get better. Right now he's at the bottom still on his side.