Right i just bought 2 small goldfish yesturday and placed them in my tank, im not really an expert on cleaning it out though..

I have seen that you replace the filter cartridge every month or so.. which is easy, but what do i do about the cleaning of the tank? I saw that you replace about 10-20% of the water each week.. do i need to take the fish out of the water when doing this?

Also, when am i meant to get rid of all the water and replace it all?

thanks

There is NO NEED to replace the filter cartridges. These cartridges (which are usually made of foam) form the bulk of the aquarium's biological filtration, which breaks down harmful waste substances which are a by-product of fish metabolism. By replacing the filter media all in one go, you will destroy all of the beneficial bacteria that colonize its surface.

There is also no need to remove the fish during maintenance, the fish will be perfectly fine whilst water changes are carried out. To carry out water changes, you will need a gravel siphon to remove the aquarium water and remove any trapped detritus and uneaten food from the substrate. I recommend a weekly 15-25% water change. Smaller, yet more frequent water changes are much better than one large water change every month or so.

It is generally inadvisable to remove more than 50% of the aquarium water, the exception being during a period of poor water quality where you need to perform a large water change to bring harmful ammonia and nitrite down to safe levels and to remove any harmful chemicals that may have entered the aquarium. Very few nitrifying bacteria actually live in the water column, however performing large water changes when they simply aren't necessary will only upset the ecological balance within the aquarium.

Every year or so, I perform one 60-75% water change as part of a 'spring clean'. The other 25-40% of the aquarium water is kept, however. Now is also the correct time to start replacing the filter media. Filter media loses its elasticity with age and as such its available surface for biological filtration starts to diminish after a year or so. The filter media should be replaced at a rate of 25% every six weeks, to allow the new media to become biologically established. In planted aquariums, specialist plant substrates that have lost most of their nutriment and mineral content can also be replaced.