There are many misconceptions floating around (get it?) about fish and fishkeeping.
Fish only grow to the size of their tank
Each fish grows to the size that it is meant to be. In order for a fish to be healthy and lead a long life, it needs sufficient room in its tank.
You need to add salt to keep your fish healthy
Freshwater fish do not need any salt in their water. Keeping salt in the water will result in stressed fish who will be more likely to contract diseases.
Fish require a pH of exactly 7.0 to live
The water in nature is almost never 7.0. Some fish do better in water that is more acidic and some do better in water that is more basic. Almost all fish can live in water as long as it has an acceptable pH range between 5.5 and 8.5.
Algae eaters and scavengers are necessary in an aquarium
This myth may be perpetuated by pet store owners who want to sell the scavengers. It is tempting to believe that there are creatures which will clean the tank for you, but unfortunately this is not true.
Your tank needs to sit before you add fish
Some people think you need to let your tank sit for a specific period of time before you add any fish. This is false; you can add your fish immediately.
The smaller the tank, the easier it is to keep
There is the same amount of maintenance necessary in a small tank as a big tank. In fact, in a small tank, a problem such as disease or algae need to be taken care of much quicker.