|
Several problems with your tank.
a 200 liter is what, like... 75 gallons or so?
Goldfish are temperate water fish, which means they require lower temperatures than tropical fish such as the silver shark and angelfish.
Your tank sounds overstocked to me. The goldfish (even if it didn't require different temperatures, which it does) would need 30 gallons for the first fish and atleast 20 gallons for each other one, but most goldfish get 8-12 inches and need quite a wide tank to turn around comfortably in. The sharks get to about a foot in length, which requires a wide tank to navigate. I would try getting the goldfish into another tank to start with.
Also, could you post the ammonia, nitrite, and nitrate numbers. The temperature you keep your tank's water also is needed. What foods do you offer other than the pellets? What kind of hiding areas and/or plants do you have in the tank?
|