silvertip shark

Question
Ok I have a silvertip shark catfish and he used to go to the top of my 15 gallon tank and swim back and forth, but since i put my aqua frog and this blue fish in he goes to the top then at random swims with his belly up at the surface of the water. i just noticed him doing it today on June 2 and it worry's me a little. i also noticed that my frog has been trying to eat him and my two bottom feeders, but the blue fish is biting my shark and my bottom feeders hard because you can see missing part of there fins. should i get rid of my blue fish and frog so they don't kill my shark? and is my shark still acting normal? someone please help i don't want my shark to die.

Answer
Danii,

The first problem is the tank size. You will need a 125 gallon tank minimum. He will soon outgrow that tank as well. 175 gallons would be perfect for him. He also needs brackish water. That means he needs salt. I would remove the shark from the tank immediately and put him in the right conditions or he will die.