You’ve chosen well, young Padawan.

Fishless cycling has become more popular over the years, as fish keepers have become more aware of the dangers involved with fish-in cycling (to their fish), the inhumanity of it all, in addition to the speed at which cycling an aquarium can be obtained with the fishless method. Whereas fish-in cycling can take months to colonize with beneficial bacteria (BB), fishless cycling can take approximately 2-3 weeks (sometimes longer, depending on the size of the aquarium).

There are several ways to fishless cycle a tank. You can use pure ammonia (my preferred method), drop some flakes of fish food in the tank, or drop one raw shrimp in the tank (usually in a media bag or even an unwashed stocking to keep it from getting too messy). For purposes of keeping things simple, I’ll be discussing the pure ammonia method below. If you’d like to attempt the other methods for some silly reason, please click here for Cycling With Flakes and here for Cycling With Shrimp.

Ok, so get on with it!

Very well. I’ll list the method via numerical steps, so as to make this as simplistic a process as I can possibly make it. Let’s get started.

*Please note that throughout this entire process you should not change any of the water. Doing so will hinder your BB colonization and WILL delay your cycle. Please be patient throughout the process. I know how eager you probably are to add fish, change things around, etc. Also, you CAN add plants to your aquarium while cycling, BUT some plants can delay your cycle, because they’ll consume Ammonia, as well, and will compete with your Nitrosomonas marina bacteria.

Step 1: Purchase your aquarium, filter, heater, thermometer, substrate, any decorations you’d want (including plants), dechlorinator (ie – Flourish Prime), API’s Freshwater (or Saltwater – depends on your needs) Master Test Kit and pure, plain, additive-free Ammonia.
– The purest ammonia you can find can probably be found at the Dollar Store or a smaller hardware store, like Ace (not Home Depot or Lowes – they both have ammonia with additives). You can buy about a liter or so at the Dollar Store, you guessed it… for $1.
– You will need the Test Kit to make certain your adding the correct amount of ammonia, in addition to testing your water’s parameters (checking for ammonia, nitrites and nitrates).

Step 2: Rinse your filter out with cold running tap water and fill it with sponge media (which is the mechanical filtration) and bio-media (which is your biological filtration – this is where your BB colony will grow). Your sponge can, however, hold a good amount of BB, as well. This media is all you’ll need. You won’t need anything else, including carbon (which is chemical filtration), ammonia-eating filtration that can be purchased (this defeats the purpose and won’t last forever), or anything else that isn’t a sponge or bio-media.

Step 3: Fill your aquarium with tap water, add dechlorinator, and add your substrate and decor.

Step 4: Raise the temperature of your heater to 82’F. You can keep it at your regular temp for your fish, but raising the temperature will create an optimal environment for growing your BB colony. They enjoy warmer temps.

Step 5: For fish tanks less than 40 gallons, add approximately 2ppm of pure Ammonia to the tank. Anything bigger and you should add about 4ppm. You can add this drop by drop or fill the cap up, using the threads as measurement and pour it in, or using your best judgement, just pour a little bit from the jug. From this point forward, I will be referencing dosing requirements for tanks less than 40 gallons. The same calculations (not numbers) apply to larger tanks. If you have questions, just ask.

Step 6: After about an hour, allowing your filter to move the ammonia around, use your Test Kit to check the Ammonia. If it reads 2ppm, you’re ready to go. If it’s less, continue to add more until you’ve reached 2ppm Ammonia.

Step 7: After 24hrs, test your Ammonia params to see if they’ve dropped. If they have, you’re on your way to colonizing Nitrosomonas marina (the Ammonia eating bacteria). The amount of time this takes differs from tank to tank.

Step 8: Now that your Ammonia is dropping, you can begin testing for Nitrites. This may take one, two and sometimes three ore more days (again, this depends on the tank). Your Nitrosomonas marina bacteria requires time to grow – enough time to eat all of the ammonia you’ve added to the tank.

Step 9: Continue to test, once per day, until your Ammonia reading has dropped to 0ppm (while still testing for Nitrites). If you have 0 Nitrites and your Ammonia has dropped to 0ppm, then dose the same amount of Ammonia you dosed before, depending on the size of your tank (2ppm). If Ammonia hasn’t dropped to 0 yet, or Nitrites aren’t present yet, don’t get discouraged. Every tank is different and not one tank will cycle as fast or slow as another. Be patient.

Step 10: Continue to test your parameters every 24 hours. Once you’ve reached a reading of 0ppm Ammonia and you have a reading for Nitrites, cut your dosing in half to 1ppm. If Nitrites are present, you have a nice colony of Nitrosomonas marina building, and you’re about to start building a colony of Nitrospira (the Nitrite eating bacteria).

Step 11: Continue dosing 1ppm Ammonia per day (when Ammonia drops to 0ppm – usually 24hrs will do it) and continue testing for Ammonia, Nitrites and begin testing for Nitrates. The forming of Nitrospira typically is the longest portion of the cycle, so it may take some time (possibly a week or two) to see Nitrites begin dropping and to start seeing Nitrates.

Step 12: Once you have a reading of 0ppm Ammonia, 0ppm Nitrites and 20+ppm Nitrates (more likely 60+ppm) you’re cycled!

Step 13: Do a 50-75% water change to decrease your Nitrates. You want a Nitrate reading of <= 20ppm (preferably <= 10ppm). Since the BB is in your filter, you can conduct as many water changes after your cycle, that you need to, until you've reached 0ppm Ammonia, 0ppm Nitrites and 10ppm Nitrates. Just be sure to use dechlorinator before adding the new water (for every water change). Chlorine CAN and WILL kill your newly grown BB… and after all of this work, you wouldn’t want to do that, would you?!

Finally: That’s it! You’re done and you’re ready to add fish, invertebrates and whatever else your big heart desires.

If you know what you’re doing and this isn’t the first time you’ve cycled a tank, you can fully stock the tank at this point, depending on if you can surmise how much biological bacteria you’ve grown in the tank. Your bio-load should provide your BB with enough food to live on a daily basis. If you grew enough for a full bio-load in a 75gal tank, then do your BB a favor and stock accordingly.

If you’re new to the game or you like to take your time in adding fish, only add as many as you’re comfortable adding. Keep in mind, however, that if you do add only a few fish in the beginning, you’re killing a good portion of the BB that you grew and you’ll only be able to add about three fish at a time, within a week or two of each other (ie – Week 1 = add 3 fish, week 3 = add 3 more fish, etc).

If, for some reason, you don’t have the stock you want yet, but don’t want your BB to die, just continue to dose 1ppm of Ammonia every 24hrs. This will keep your BB alive, but it will also end in raising your Nitrates. So, once you’re ready to add fish, you’ll need to do another large water change to take care of those Trates.

If you have questions, feel free to ask!