Fishless Cycling

by Fish Tank on July 2, 2007

When I first entered the hobby, I did a lot of research. One aspect of starting an aquarium, deals with the fish cycle, or nitrogen cycle. Fish stores and pet shops will usually give you the advice that it's best to slowly introduce fish into your tank. They'll sell you fish that are "tough", and can make it through that first period. I have never used that method. When cycling a new fish tank, I believe the best way is to use the fishless cycling method. You're now saying to yourself... The fishless what?! Yes. The fishless cycling method.

First, it will help to explain what cycling your tank actually is. Fish waste is fully of deadly ammonia. Fortunately, bacteria grow that eat the ammonia, and turn it into nitrite. This bacteria is called Nitrosomonas. It grows within a matter of days in the proper conditions, and eliminates the ammonia from your aquarium. It's waste product, nitrite, is also deadly to fish though. Another bacteria comes along, Nitrobacter, and eats the nitrite. Nitrobacter produces a waste product, nitrate. In small quantities, nitrate is safe for your fish. So instead of slowly building up these good bacteria by slowly introducing fish, fishless cycling prepares the aquarium for many fish at once. Benefits include:

  • Less stress on your fish.
  • Fish are never exposed to deadly ammonia and nitrite.
  • Ability to add many fish at once. (I've added 7 neon tetras, and 2 gouramis at once. The gouramis don't view the tetras as food, because they were all added when small in size.)
  • Fishless cycling is closer to a "natural environment" than adding fish to plain dechlorinated water.

So how do you do fishless cycling?

You add pure ammonia to your aquarium before adding fish. Now this method requires the same amount of patience as cycling your tank with fish. It took 4 weeks for me to cycle my 37 gallon eclipse aquarium. The nice thing was that I didn't lose a single fish, when I put them in all at once!

I'm not a scientist, nor do I play one on tv, but here's how I perform fishless cycling for a freshwater aquarium. I use ammonium chloride NH4CL, which I bought at a local store that sells chemistry supplies. You want to be careful about adding ammonia you find in some stores. They may contain perfume, or other unwanted additives.

First, I spike the ammonia level in my fish tank by adding the ammonia. You want it to reach 1 - 2ppm. It took 15 drops in my 37 gallon Eclipse tank to get the spike I needed. Test ammonia levels, and nitrite levels daily, before adding ammonia. I used a water testing kit.

I kept adding 15 drops, once a day. On the fourth day, I checked my ammonia level before adding any drops. The test was showing no ammonia was present. The Nitrosomonas bacteria was growing, and doing it's job. I had been checking nitrite levels every time too, and saw an expected nitrite spike.

Cut the drops you use daily, in half, when the nitrite spikes. In my case, I went to 7 drops a day. After 4 weeks of adding 7 drops daily, enough Nitrobacter had grown. Ammonia and nitrite levels were 0.

At this point you'll want to do a water change. Empty half the aquarium, and add dechlorinated water. The reason for this, is you want to clear an excess of nitrates that have formed. Add ammonia for a day or two more, to make sure ammonia, and nitrite levels are ok.

Add as many fish as you want, based on the 1 inch of fish/gallon method. Remember to add compatible fish. Then enjoy watching fish that are safe from deadly ammonia and nitrite, because you used the fishless cycling method.

{ 4 comments… read them below or add one }

Paul Byrley September 17, 2007 at 9:15 pm

I sucessfully used fishless cycling with regular household ammonia from Food Lion supermarket. The various bottles were clearly marked when they had perfume or cleaning materials so I could avoid those and get plain ammonia. I already had test kits for ammonia and for nitrite & nitrate. I thought it was pretty neat. BTW, when I started, I put a plastic plant in from my existing 30 gal tank. It had some algae on it so I assumed it also had cultures of the bacteria I needed. I think that’s better than just new water and ammonia and hope the right bacteria happen to blow into your new tank. I put some guppies in after about 3 weeks and they did fine with no fatalities and soon I had too many guppies.

Fish Tank September 19, 2007 at 2:08 pm

Hey Paul,

Don’t tell anyone, but I’ve used household ammonia successfully too 🙂 I just wanted to make it clear in the article that combined perfumes wouldn’t be good. We may enjoy a lemony fresh scent, but I doubt the fish do.

Fishless cycling is pretty cool. When I first tried the method, I did use some water from an established tank. I don’t anymore. The bacteria seem to grow with no problem. I am using a biowheel on an Eclipse canopy… which I really like. That may help with bacteria growth.

Good luck with the guppies.


Fishman Jack October 30, 2008 at 3:18 pm

Fishless cycling is nothing new, but there is a quicker way to do it. First of all, add some old gravel from an already cycled tak that has been set up with a standard undergravel filter. Next add your ammonia source and then neutralize it with ClorAm-X and sit back and monitor the nitrite and nitrate. Once the nitrite has gone and nitrate starts to accumulate then add the first fishes from the quarantine tank.

Fishman Jack

Fish Tank November 3, 2008 at 5:51 pm

Hi Fisherman Jack,

Yes, a person can add some gravel from an established to to help the process along. I’d guess it still takes some time for the new bacteria to grow though?


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