Fishless Cycling Guide

How to Cycle an Aquarium with Ammonia

You can start your fishless cycle 24 hours after you have set up your aquarium, filled with dechlorinated water and turned on the heater and filter.

Shopping List For Fishless Cycling

There are a few things you’ll need to buy to carry out your cycle. This looks like an expensive list, but most of the items listed will be needed irrespective of how the tank is cycled. The only extra is the purchase of a bottle of ammonia and the cost of that will be less than you would spend on extra dechlorinator when doing daily water change for a fish-in cycle, or a LOT less than the cost of treating fish for ammonia burns, nitrite poisoning, bacterial infections and so on that may well arise in fish introduced to an uncycled tank. Here is what you will need, apart, obviously, from the aquarium itself:

  • Bottle of household ammonia with no additives. This may be available at a local hardware store or is usually available on eBay or Amazon. The Kleenoff brand is suitable.
  • A liquid type aquarium water testing master kit including tests for ammonia, nitrite, nitrate and pH. Kits by API and Nutrafin are recommended. Paper test strips are not suitable as they are too inaccurate.
  • A syringe for dosing the ammonia, available from any chemist
  • A bottle of tap water dechlorinator/water conditioner
  • A small pot of fish food – preferably flakes
Getting Started

Fishless cycles are usually conducted using between 2 and 5 ppm of ammonia, dependent on how many and what types of fish you will be stocking. Choose your cycling level and stick to it throughout the fishless cycle. Don’t exceed 5 ppm as dosing higher than that will probably prevent the beneficial bacteria from growing. To get your fishless cycle underway, calculate how much water is in your tank. This will be the actual tank volume minus 10-20%  for the space taken up by sand, and decor. Underestimating volume is safer than overestimating because an overdose may stall the cycle. You can use the calculator below to work out how much ammonia to add to the tank.

Ammonia Dosing Calculator
Current ammonia level (ppm):
Desired ammonia level (ppm):
Water volume (litres):
Ammonia to add (ml):

Use your ammonia test to check the level is correct; thereafter test the ammonia level daily. After approximately 10 days bacteria should be growing and as a result, the ammonia level will be beginning to fall. The bacteria which “eat” ammonia consequently produce nitrite hence as the ammonia level falls, nitrite rises. You can use the calculator again to work out how much ammonia to add to bring ammonia  back up to your starting level whenever it falls to less than 1 ppm,

Ammonia will reduce faster as the cycle progresses and the level of nitrite will rise more quickly. Nitrite may appear to stick at the highest level on your test kit’s scale for a considerable time, but this is an illusion due to the test kit’s limited range. The reality is that nitrite may climb beyond the limit of the test thus, as a result, you may be unaware of nitrite starting to fall as the cycle progresses. Testing for nitrate from this point on will guide you because as nitrite reduces nitrate will rise.

fishless cycle aquarium illustrationFurthermore, when nitrite starts to be fall, you can add a few flakes of fish food in addition to continued ammonia dosing. This can help during this stage of the fishless cycle, probably because fish food contains additional nutrients which nitrite munchers seem to like.

How do you know when a fishless cycle is complete?

The cycle is complete when you can add a dose of ammonia and test results 12 hours later show 0 for ammonia and nitrite. At this stage nitrate will have risen to a very high level, therefore, you’ll need to do a large water change (maybe more than one) to reduce nitrates to an acceptable level for fish. It’s advisable to continue dosing ammonia once a day for a further few days just to be sure, then do a final water change and you’re ready for your first fish.

Every fishless cycle is different, but typically, an initial cycle on a new set up will take around about 4 weeks. Some take longer, some less time than that, especially if you can get hold of some filter media from a mature tank to kick things off. In conclusion, if you encounter any problems with your fishless cycle why not ask a question?

Questions about this? Click here.

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