Goldfish grow to the environment in which they are kept and have growth spurts all year round when kept in an indoor aquarium. They grow to 8+ inches for the fancies and 12+inches for the normal single tailed (shubukins, comets, albino and golden commons). 40l is not enough for any goldifish so that wiki article is wrong if it states that, the minimum for a goldy is 30 gallons and 15 gallons extra for every additional goldfish. They are big fish if kept in the proper environment and will live for 20+ years. Filtration should be triple the tank capacity due to their inefficient digestive system they are messy.
albino frogs can be kept with goldfish and any tank which is fit for an adult goldfish is fine for the ACF (african clawed frog)