Yup, good to know! So 12 hours past your testing point(the "24 hour mark" I like to call it), will be where you will know if your tank is cycled or not. If at 12 hours past the 24 hour mark your ammonia and nitrite are at 0 ppm, then you are cycled!
After this happens, continue cycling the tank for one more week. This is called the qualifying week where nitrite is sometimes prone to fluctuate; for unknown reasons. It is best to have this happen without fish in the tank.
After the qualifying week is up, go ahead with a 90% water change, re-add dechlorinated, hand-temp-matched water and and fish!
Here is the fishless article I wrote taken from the book I am writing:
Fishless cycling:
Since fish produce ammonia and since ammonia is what the Autotrophic bacteria need to start the nitrogen cycle, why can we not just buy a bottle of ammonia to simulate fish?
*It is a really good idea to start a log of your tank for a fishless cycle.* So for each day you take a reading of ammonia, nitrite, nitrate and pH, you can then put that in your log so you can see how the cycle is coming along.
Step 1: Buy a bottle of ammonia, usually ammonia comes in bottles with 9.5% or 10% diluted ammonia, both will work. Ammonia like this can usually be found at your local hardware store. What is very important about what ammonia you select is that it must only contain ammonia and water. Other additives will hinder the ammonia useless and will not allow the bacteria to grow. If the bottle of ammonia does not list ingredients, then that bottle of ammonia is most likely okay to use, but to make sure give the bottle a good shake. If the ammonia foams up, it is no good. If there are a few air bubbles, then that is nothing to worry about.
Step 2: Add up to 5 ppm of ammonia to your tank by looking at the table below. It is very important that you add the ammonia on a 24 hour schedule.
Step 3: Check the ammonia level by using your test kit to make sure you have added the correct amount of ammonia.
Step 4: Check the ammonia level every day at the 24 hour mark. If the ammonia at the 24 hour mark starts to go down, this means that you are starting to colonize bacteria that process ammonia. At which point the nitrite level will begin to rise. You can then use your nitrite test kit to monitor your nitrite level.
Step 5: At the 24 hour mark, if your ammonia level is nearing 0 ppm, add ammonia back up to 5 ppm. You will soon see that your ammonia level is dropping faster and faster and that your nitrite level is rising. Over time, after adding ammonia back up to 5 ppm at the 24 hour mark for a couple weeks, you will begin to see your ammonia level will soon go down and hit 0 ppm at every 24 hour mark and your nitrite will be either rising, or starting to fall. At this point your nitrate will start to rise.
Step 6: If your ammonia and nitrite are at 0 ppm every 24 hours, then it is time to start taking ammonia and nitrite readings every 12 hours. So let’s say you add ammonia back up to 5 ppm at the 24 hour mark, and then 12 hours later you test your ammonia and nitrite, this is where you will be able to tell if your tank is cycled or not. At this point, your nitrate level will be at a pretty high level, but do not worry about this yet.
NOTE: It is VERY important to ONLY add ammonia at the original 24 hour mark! Not the 12 hour mark! If you are reading 0 ppm of ammonia at 12 hours, then wait until the 24 hour mark (12 hours later) to add ammonia back up to 5 ppm.
Step 7: Once your tank is reading 0 ppm of ammonia and 0 ppm of nitrite at 12 hours, (12 hours after the 24 hour mark) you are nearly there! At this point, continue dosing ammonia up to 5 ppm at the 24 hour mark for one more week! This last week is called the “qualification week.” During this week you may have a slight nitrite spike; this is why you should always perform the “qualifying week.” Once the week is over, and you are getting both 0 ppm of ammonia and 0 ppm of nitrite (double 0’s) then you are cycled!
Step 8: Now do a 90% water change, this is to lower the level of nitrate. Add water back up to full in your tank and add the proper amount of water conditioner. Then you are ready to add your full stocking of fish!
Here is a little example on what I mean about the 24 and 12 hour marks.
Let’s say you start your fishless cycle at 8:00 pm. This means you add your first batch of ammonia up to 5 ppm. The next time you check your ammonia level then would be the following day at 8:00 pm (24 hour later, hence the “24 hour mark”). When your ammonia level starts to drop near 0 ppm at the 24 hour mark (8:00 pm) then go ahead and dose the ammonia back up to 5 ppm. If you are consistently getting a reading of 0 ppm of ammonia every 24 hours after you have added the ammonia back up to 5 ppm the following day, then go ahead and start test for ammonia at 12 hours. EX. Add ammonia up to 5 ppm at 8:00 pm, then at 8:00 am check the level of ammonia. If the level of ammonia is at 0 ppm at 8:00 am, DO NOT add ammonia until the 24 hour mark (8:00 pm).
-FHM
