Anyone can keep fishes , no matter how small their home , and they are particularly suitable for apartment-dwellers , especially those in highrise blocks where the keeping of other pets may be impractical or even prohibited . There are other advantages too ; Fish won’t need exercising , They do not disturb your home with messy fur or feathers , They can not escape like other pet reptiles , They can not make noises . All you need is a space to put your aquarium . Aquariums require a few minutes of your attention daily . Although it depends on which aquarium type you choose , it won’t cost so much money . Piranhas are tropical freshwater fishes , you don’t need to buy so many complex machines . As you start your aquarium hobby you will acquire new knowledge and skills . For example the fishes behaviour , biology , their nature , ecology and so . Piranha.org will help your knowledge about Piranhas . Also don’t forget fish keeping is an ideal way to introduce a young person to animal care . When you are selecting your aquarium for your piranhas you will meet three major criteria to consider . Shape , Size And Construction . Fish require oxygen for respiration , while selecting your aquarium tanks let the surface larger this helps the carbon dioxide leave from the tank . Fish produce carbon dioxide as a waste product of their metabolism , you should rapidly get rid off carbon dioxide . There are 2 main ways to get rid off carbondioxide one is larger surface and the other is air stones . There is a kind of stone which you can find in every aqua hobby shop , and also there is a pumping device this pumps the air , when you connect this two devices together and put the airstone part in the aquarium they will produce enough oxygen for your fish and will make bubbles . This bubbles makes oxygen in the water and kills carbondioxide . We will review this later on the step by step aquarium making part later . The shape of your aquarium is too important . When selecting an aquarium , always take into consideration the number , size and behavior of the fishes you wish to keep . Larger fishes require more water and more bigger aquarium . Although piranhas are not usually active fish many are quite territorial and tend to persecute each other when not given adequate room to disperse . Do not choose tall tanks or drum bowls kind tanks.