Small fantail goldfish are about 3.00
Do not buy the comet goldfish! Though they are the cheapest, they require the largest tank. They will get up to a foot in length, and are really only suitable for ponds.
~Okay, I'm sorry but that tank is not suitable for even a single goldfish. A pair of goldfish require a twenty-nine gallon tank minimum, and a very efficient filter.
~Goldfish are very large fish. The common or comet goldfish reach about a foot in length, while the fancy varieties reach 6-8 inches. Nitrates build up easily in such a small tank, and inhibit growth. This stunting leads to an early death.
~The general lifespan of a common goldfish is 12-20 years. When kept in a small tank with insufficient filtration, they commonly live about four years. That is disgraceful for a goldfish.
~All types of goldfish are very dirty. They produce more waste than other types of fish. The waste they are constantly giving off becomes ammonia. In any amount ammonia is lethal to fish. The only way to avoid a problem with ammonia, is to have a very large tank, and an extremely efficient filter.
That size tank is perfect for a single betta. The tank should run for a minimum of three days before adding fish. Don't forget water conditioner.