There are two types of costs to think about when you decide to build a system, construction costs and maintenance costs. You only have to pay construction costs once - when you build the system. Maintenance costs include things like food, electricity, and repairs. These are paid for as long as you have the system. Estimates for construction costs (below) and maintenance costs (opposite page) for the two different systems are shown. By 'crop' I mean the time to raise and harvest a group of fish from fingerling to eating size.