Columbian Shark rubbing other fish?

[kraiz]

Hey,

i have a columbian shark that always swims directly under the other fish, actually touching them... he always does it to all the fish. Any ideas why?

 

[Tony]

What are your water parameters?

The aragonite sand in your tank is probably making the water pretty hard, which the shark (along with the Dempsey and the eels and the barbs) is not liking all too much.

 

[Prince]

it probably nothing however you should read this: http://badmanstropicalfish.com/profiles/profile63.html

You are going to have problems in the future.