Fishless cycling

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What is "Nitrogen Cycle"?[edit]

Before we get into fishless cycling, we need to understand what "cycling" or "nitrogen cycle" is. Click to read more on the nitrogen cycle. In brief, the cycle can be explained as:

Fish produce waste in the form of ammonia. Also uneaten food adds to the ammonia. Ammonia is extremely poisonous to fish. There is a set of (good) bacteria which convert the ammonia into nitrites. Nitrites are also slightly less poisonous to fish. There is another set of (good) bacteria which convert nitrites to nitrates.It takes considerable amount of time to develop these bacteria (and start the cycle). Nitrates are not very good to fish either but can be removed from the water by regular water changes.

What is "cycling"?[edit]

When the tank is newly setup there is no bacteria establishment to convert ammonia to nitrites and then to nitrates as explained above. Cycling is the process of establishing the bacteria colonies which will mostly be in the filter media.

There are several ways to cycle a new aquarium.

  1. Fishless cycling with pure ammonia;
  2. Fishless cycling with fish food or a piece of dead shrimp/fish;
  3. Cycle with fish.

What is "fishless cycling"?[edit]

Historically the way to start the cycle was to introduce a few "hardy" fish to the new tank. The fish would produce ammonia which would help start the bacteria colony. These supposedly "starter" fish were hardy enough to tackle the ammonia and nitrites before the bacteria colony establishment. Though this works in most cases , it is definitely not humane since these starter fish may survive but they may have permanent long term organ damages. Fishless cycling as the name suggested is the process of bacteria establishment or "cycling" without any starter fish.

All it takes to some kind of an ammonia source. This can be a raw shrimp (or prawn) bought from a fishmonger, or your local supermarket, thrown in the tank or some fish food added to the tank to kick-start the ammonia generation. Both these options can foul the tank water and helps to breed unwanted bacteria. Another option is to use pure ammonia available in most home improvement stores (Kleen Off) or Garden shops. If using this option, make sure the ammonia is free of any surfactants as they may hurt the fish in long term. To test for surfactants, just shake the ammonia bottle before purchasing and if it fizzles or gives bubbles then there are surfactants present. Also use only pure ammonia — that is one which is not scented.

To start the cycling, keep adding one drop of ammonia per gallon of the tank, to the tank water. Keep adding that amount of ammonia till there is an ammonia spike in the tank (5ppm). After the spike, keep adding half that amount daily. Soon enough you will see a nitrite spike which will lead to a nitrate spike.

Finally ammonia (NH3) and nitrite (NO2) will reduce to 0 even after adding the ammonia and there will be a large amount of nitrates (NO3) in the tank. Make a 50-60% water change and the tank is ready for the fish.

The big advantages of the fishless cycling are :

  1. It is a humane process as no fish is involved
  2. You can fully stock your tank at once if you have completed the cycle with high concentration of ammonia. (remember not to overstock though)

It is very important to have a reliable water testing kit that lets you test ammonia, nitrItes and nitrAtes present in the water.

Special notes[edit]

  • Ensure your water in your tank at the start of this fishless cycle has a reasonable level of GH and KH, say above 5d (89.3ppm) and a pH above 7. That is, it is at least medium hard water. Some species of nitrifying bacteria have trouble growing in soft water. You can add a quantity of Lime, Coral sand and/or Bicarbonate of soda to address this issue.
  • High levels of ammonia are known to inhibit the growth of NitroSpira (the nitrite to nitrate bacteria) so keep levels of ammonia no more than 5~6ppm)
  • Extreme low PH will slow or stall the bacteria growth. When nitrate is produced, it will make the water acidic. Once the water buffer is gone, PH will crash. Do partial water changes to restore water buffer and water PH when the nitrate is too high.