The short answer is anything from 5 to 15 years. Acrylic tanks don't last as long as glass aquariums. However, this is not necessarily true. If the structure is sound and you maintain your acrylic tank well, you should be able to get up to 15 years of use from one. As with glass aquariums, you will not get long service from your acrylic tank if you don’t maintain it effectively. Treasure your aquarium and you will get many years of joy from your acrylic tank.