Isn't the Tropiquarium88, 130 litres? 2 silver sharks (bala)? That doesn't seem wise to me - My original tank had one silver shark and 3 silver dollars and that was 180 litres (I bought the tank with the fish). I ended up giving the silver shark to my friend who had a 300 litre tank. They grow up to 13 inches or 33cm as adult fish.
It is said that 1 bala shark as an adult should have about 50-55 gallons or around 250 litres.
Also, you asked for tips etc... It's a myth that fish grow to the size of the tank. Also, don't overfeed as it will affect the water quality. Feed two times a day about two small pinches of food.
Get to know the fish, and the species in the tank and what they require and try to provide them with a good environment in the tank. Unhappy fish are stressed fish, and it can lead to disease and illness.
