Hi Joza and Welcome to our "new freshwater tank" section!
Twinklecaz is right and you are one of the super-lucky ones who has stumbled on this subforum prior to the LFS (local fish shop) sending you home with a big load of fish prior to you having a working filter to care for them!
The story of what gets a tank ready for fish turns out to be two wildly different stories, depending on whether you hear the one in the LFS or the one in a serious hobby forum like this one
. Which story you want to take to heart is your own choice of course but we can try to tell you both stories if you're interested. The story at the store is carefully tailored to try and not lose you as a customer during the 1.5 minutes average they have your attention. The story we have to tell is tailored around the long hot lazy days of spring that mother nature actually uses in the "real" environment where baby fish begin their lives in streams and ponds, lol.
Believe it or not, one of the core aspects of the hobby is growing and learning about two particular species of bacteria that we grow in our filters to transform the filter from being a near-worthless piece of hardware into a living, working key part of our tank system called a "biofilter!" The "food" (if you will (actually its not food in the traditional sense, as its not really ingested, but processed by the bacteria)) for these bacteria comes from simple ammonia. Ammonia is a Nitrogen source (formula for ammonia is NH3.)
We provide this "bacteria food" source, along with fresh water that has oxygen and a few trace things that tap water has and we supply them steadily by having the filter pump them constantly past a nice "surface area" provided by stuff in our filter like sponges and other things. It turns out that our two bacterial species are so "everywhere" on the planet that some of them will be in our tap water and these can be our tiny supply of "starter bacteria." (The LFS often try to sell "starter bacteria" but this depends on the customer not understanding that bacteria need fresh oxygen and ammonia each day or they will be dead!)
Given the right conditions, these very few starter bacteria will (slowly) multiply and grow to be the two large colonies of millions and millions of bacteria and reach a point where they are able to clean the water of the waste products that can cause our fish to become ill or die.
~~waterdrop~~
