Do you actually have these fish yet? 40l is only about 10gals- this is too small for even a single goldfish. I would do some searching on here for suggested fish that are appropriate to stock a 10gal tank. If you would like to stock goldies, you will need a much bigger tank. Fancies need atleast 20g for one fish, 10gal for each fish after. Commons/comets/shubunkins are realitically pond fish & really should not be kept in an aquarium unless its very large (50g per fish). They can grow to be up to 18inches. Ill post a link fo
strating a fw
aquarium. In it are also links to fishless cycling & fish-in cycling. Good luck & please dont hesitate to ask any questions!!!