depends what fish. gold fish are easy. just simple gold fish flakes from you supermarket or pet store. once a day.
to clean their cage, scoop out 1/4 of their water and put it in another bowl or container. then use a net or sieve to put them into the container. then pour out the rest of the water through a sieve (to stop the pebbles falling into the sink) and replace the water. you will need to add chemicals so the water is ok for the fish. then once the water has settled and the chemicals have done their stuff (usually takes a day i think) you can ut the fish back in. this will only need to be done once a month or so.
but every week take out a quarter of the water and replace it with water that has been sitting outside for 3 days or water with chemicals added to it.
keep the tank out of sunlight so not too much algae grows and a couple of snails cant hurt. they help keep the tank clean.
talk to the people in the pet shops they will know more than me. its been a while since ive had fish.
tropical fish will need more care and you would need to talk to pet shop owners to find out more or someone else that has tropical fish.
