Introducing a new filter to an establish tank

[P1nkielady]

Hi

I've just 'inherited', for want of a better word, a 50l fresh water tank, with 3 small goldfish in it, there is a pump and about 3 live plants in it! I've read that it would definitely need a filter which I don't mind buying, however, I've also read about using old filters alongside new ones, which obviously isn't an option, is there any advice on introducing a brand new filter to this tank.

 

[Mebbid]

If you have a fish tank that's established you can just move some of the media over. If not then you are doing a fish in cycle.

Take a look at I just learned about cycling but I already have fish. What now?! - Aquarium Advice