Cycling-next step

Question
Hi,

I have had a Biorb Life 45 (12 gallon) tank for 4 weeks. After setup, left for 1 week before adding 3 small guppies. After 2 weeks all the fish died suddenly overnight. I tested the water to find pH fine, ammonia 0, but nitrites over 3. I am assuming cycling process progressing ok but not sure what to do now. Will the cycling process stop as there are no fish? Should I leave the tank and keep testing until nitrites are 0?

Your help would be much appreciated.

Answer
Martin,
It is always best to do the cycling without fish. Here is how I cycle my tanks.

Set up the tank with everything that will go into it except the fish. Gravel, water that has been conditioned, filter, decorations, and a heater if the tank is going to be tropical. Once everything is in the tank plug in the filter and the heater. In a few days you will see that water starting to cloud up. That is ok, it is natural. After the tank has been running for about a week or so, the first of two bacteria blooms with begin. This first one is the bad stuff that is not healthy for fish to be in. At this time you will start to "seed" the tank by adding fish food. The food will then start to rot bringing in the ammonia. Feed the tank for a week.  When the feeding is done, the second bacteria bloom will set in. This is the bacteria the gravel and filter need to keep the fish healthy. after 1 to 2 weeks after you stop the feeding of the tank, you will start to test your water for ammonia, nitrites, and nitrates every day. The readings will be high to start with. After testing, do a 30% water change. You will test daily. IF, while testing, you get no readings for ammonia, or nitrite for 5 days in a row, the tank is cycled and you can start adding fish in small numbers. But, if during the 5 days of testing, there is still a reading, the 5 day testing cycle starts over. For example, say you are on your 5 day testing cycle. The first 2 days the readings were at zero. On the third day, you are registering ammonia/and or nitrites. You will do a water change, and the 5 day testing cycle start all over.

Do not add anymore fish to the tank until it is completely cycled. The whole process can take 3 to 6 weeks.