The tank is now completely cycled and can be stocked with fish.
There is a lot more work load because of the frequent partial water change required to sustain the fish through the tank cycle.
Often, when cycling a tank without fish, you lose the between when youthink the filter is ready and when you get fish, meaning after goingthrough several weeks without fish in the tank to get the tank cycledwithout fish, you introduce fish to an uncycled tank anyway, resultingin stress and losses.
Cycling the tank with fish always results in a cycled tank (assumingthe tank is large enough to cycle), but cycling without fish may ormay not leave you with a cycled tank, and the only way to tell is toadd fish.
Community fish used to cycle saltwater tanks:
How to Cycle a Fish Tank (with Pictures) - wikiHow
Your tank is fully cycled once nitrates are being produced (andammonia and nitrite levels are zero). To determine when the cycle hascompleted, buy appropriate test kits (see ) and measure the levelsyourself, or bring water samples to your fish store and let themperform the test for you (perhaps for a small fee). This processnormally takes anywhere from 2-6 weeks. At temperatures below 70F, ittakes even longer to cycle a tank. In comparison to other types ofbacteria, Nitrifying bacteria grow slowly. Under optimal conditions,it takes fully 15 hours for a colony to double in size!I would encourage all fish keepers to gain an understanding of the nitrogen cycle as this will help you understand exactly what is going on inside your tank and how you can deal with water quality problems should they arise.The simple answer is yes, an aquarium must be cycled properly before you can safely add your fish. It doesn't matter whether the tank is 15 gallons or 500 gallons, it's still got to be cycled. If you were to simply fill your tank with water and then add all your fish at once then there would be such a massive buildup of ammonia, the chances are your fish would be dead within a few days.Traditionally, there are two ways to cycle a fish tank. Both methods will involve introducing ammonia into the tank which will be the food the bacteria need to survive. The most common method of cycling an aquarium is to use small community fish that produce the ammonia themselves. A kinder, more acceptable way to cycle a fish tank is to use a method called the "fishless" cycle. This also involves adding ammonia to the aquarium, but as a name suggests you do not use live fish. In this article, we are going to use fish as it's probably easier for a beginner to undertake, and we wouldn't be happy with youngsters handling pure ammonia as it can be dangerous. If you would prefer not to use live fish then read this article on how to carry out a fishless cycle.We would recommend that you use small community fish like the Barb. The Tiger and Cherry Barb are absolutely ideal as they are quite a hardy species of freshwater fish and unlike some more sensitive species, won't turn belly up as soon as they are exposed to ammonia. If you are cycling a very small tank less than 20 gallons then you are probably better off using much smaller fish like guppies or neon tetra. Your fish store should be able to give you advice based on what fish they sell.It's important not to add too many fish as this will create a large ammonia spike very quickly which will probably just kill the fish within a few days. For a 55 gallon tank, 10 barbs would be appropriate. For a 75 gallon tank, you could go up to 15, for 100 gallons plus, you're looking around 20 upwards.It's become quite popular to kick start the cycling process by seeding your new aquarium with biological media that already contains live nitrifying bacteria.