In an aquarium, bi-weekly water changes are a good idea as a goldfish tank is hard to keep clean.
(bi-weekly water changes; are; a good idea as a goldfish tank is hard to keep clean; L:In an aquarium) (a goldfish tank; is; hard to keep clean)
bi-weekly water changes a goldfish tank
are is
a good idea as a goldfish tank is hard to keep clean L:In an aquarium
hard to keep clean