The way to judge whether the end of your fish-in cycling situation has been reached is as follows: if you can go for a week of testing ammonia and nitrite(NO2) morning and evening and getting readings of zero ppm for both without having to change any water then you can consider your filter to be cycled. If you get a day where you see traces of either poison then you restart your "qualifying week" and go forward. It can take a while for a biofilter to settle in to full operation but once it does it can remain maintainable for years and give good service.
Once your filter has passed its "qualifying week" you can consider your first fish addition. Ideally you want to add the equivalent of 2 or 3 small tropicals at a time but this varies by species. With fish as small as neons you might add a bunch of 5 at a time, whereas with small cichlids you might do a single or pair. Ideally they should be observed in your quarantine tank for 6 weeks prior to introduction to the display tank community but some will go shorter than this if they have experience trusting their LFS and are willing to take the risk. If you are a beginner without a Q-tank then of course you have to take the risk of direct introduction. Always leave at least two weeks after an introduction when your filter is under a year old as a way to let the bacteria grow to match the new bioload (the new level of fish stocking.) After your filter has a year or more of maturity it would probably easily respond in a week, but the better habit in this hobby is to learn to relax and give things time (after all, the soul of this hobby is to go in the opposite direction of forever production orientation of our busy selves, lol!)
The two major maintenance habits you will now want to establish for yourself are the weekly gravel-clean-water-change and the monthly (or so) filter maintenance session performed within one of the weekly water changes. There should be good writeups of both of these within the BRC. Nitrate(NO3) can serve as a tool to help you know whether these two maintenance habits are working for your tank. You'd like NO3 to be no more than about 15 to 20ppm -above- whatever your tap water NO3 level is but the thing you're really watching for over the weeks is whether it remains stable or drops or whether it wants to rise on you. If it were to rise you'd want to increase your maintenance actions. It is also good for a beginner to determine all the details of filter maintenance that will help the filter stay in good working order for a long time. This may involve odd sized brushes to clean the impeller and its parts and vasoline type gels to protect silicone parts.. all this in addition to the proper squeezing and light rinsing of the media in tank water that is the core action of filter maintenance.
~~waterdrop~~
