As another newbie, I will tell you in a nut shell what I think will help you (anyone out there correct me if I'm wrong, I have some background knowledge on this since I'm a chemist but most I've picked up from reading and 3month experience with my aquarium)
Cycling your tank means growing the bacterial colonies that turn ammonia (fish waste and toxic to fish) into nitrites (also toxic to fish) and nitrites into nitrates (much less toxic to fish). These bacteria live in your filter/subtrates and decorations but they grow fairly slowly so cycling takes anywhere between 4-6 weeks. (You can shorten this if you add some media from an established tank)
Don't believe the stores when they tell you to set up your tank and add fish after 72 hrs (that's what happened to me) they just want to sell you fish. Likewise don't believe they will know what kind of fish can go in your tank given your tank size and occupants again, they just want to sell you fish.
Since you already have the fish in there you can cycle with fish but this will require A LOT more work on your part to keep the fish happy and healthy. Basically you want to do as many partial water changes (PWCs) as necessary to keep your ammonia and nitrites below 0.25ppm. Your nitrates will not accumulate significantly until your tank cycles but once it does most people keep nitrates below 40ppm. In a cycled tank that is not overstocked a weekly 25% PWC
should be enough.
While your tank is cycling you will need to test your ammonia/nitrite/nitrate/pH at least daily to make sure the water is safe for your fish, so get that test kit, liquid is more accurate than strips. I had to do 50-75% PWCs every day for 3 weeks in my 20gal tank because I was cycling with fish.
You should use tap water conditioner to get rid of ammonia/chlorine and chloramines in your tap water, if you don't the ammonia can stress/kill your fish and the chlorine and chloramines will kill the bacteria in your tank. I personally like Seachem Prime, but there are lots of other products out there that work well too. (On a side note the products only bind the ammonia so that it is not toxic to fish, but it will still test positive in the liquid test kits until the bacteria in your tank consume it). Also, the water that goes into your tank should match your tank's water in pH and termperature, for pH not more than a 0.2 difference at most.
Another side note on PWCs, a PWC
dilutes what is your tank by the fraction of the PWC
. For example, if your ammonia is at 2ppm and you did a 50%PWC
it would bring it down to 1ppm, a 75% PWC
would bring 2ppm down to 0.50ppm. So if you had 2ppm and wanted to bring the level down to below 0.25ppm you could do either 3 succesive 50%PWC
, 2 succesive 75%PWC
(level would be 0.125ppm by the end) or a combination.
Since the bacteria live in your filter and subtrate don't vacuum your substrate and change your filter cartridge on the same day EVER, this will take too much your good bacteria out and your tank would have to cycle again (though it would probably not take as long as the first time). Also, you don't need to change your filter cartridge every month like the manufacturers say (they just want to sell you filters), just take it out and rinse it in old TANK WATER (like what you take out during PWC
), don't rinse it in tap water because the chlorine will kill the bacteria.
Finally, I read that those ammonia reducing products (like the tabs and API ammo-lock) can stall the cycle but I am not 100% sure on this. My experience is that my tank did not cycle at all while I was using ammo-lock.
Sorry for the novel but hope this helps =)