No salt needed... tropical just means you will need to have a heater to help keep the water at a warmer temperature...
Make sure that the water is properly treated...
Do not overfeed...
Do not overstock... A good rule of thumb is 1 gallon of water per 1 inch of fish (at adult size)...
The most important thing is to make sure that the tank does not leak. If the price is right and it does have a small leak at the seam (no cracks in the glass) you can buy silicone to help reseal the edges from most pet stores.
Do not buy the silicone that is used for household chores. It would...
