Axolotl Expert

The Nitrogen Cycle: The Most Critical Step

Before you ever purchase an axolotl, you must establish a colony of beneficial bacteria in your aquarium filter. This process takes 4 to 8 weeks.

Nitrogen Cycle Diagram

The Danger of "New Tank Syndrome"

If you place an axolotl in a brand-new, uncycled tank, their waste (ammonia) will rapidly build up to toxic levels within days. This burns their gills, damages their internal organs, and is frequently fatal. You must cycle the tank before adding the animal.

What is the Nitrogen Cycle?

The nitrogen cycle is the biological process that converts highly toxic waste into less harmful compounds. It relies on two distinct types of beneficial bacteria that live primarily in your filter media (sponges, ceramic rings), not in the water itself.

Step 1: Ammonia (Highly Toxic)

Axolotls produce waste, and uneaten food decays, creating Ammonia (NH3). Even trace amounts (0.25 ppm) are dangerous.

Step 2: Nitrite (Highly Toxic)

The first type of beneficial bacteria (Nitrosomonas) consumes the Ammonia and converts it into Nitrite (NO2-). Nitrite prevents the axolotl's blood from carrying oxygen.

Step 3: Nitrate (Less Toxic)

The second type of beneficial bacteria (Nitrobacter) consumes the Nitrite and converts it into Nitrate (NO3-). Nitrates are only toxic in high concentrations (above 40 ppm) and are removed through your weekly water changes.

How to Cycle Your Tank (Fishless Cycling)

You will need an API Freshwater Master Test Kit and a source of pure liquid ammonia (like Dr. Tim's Aquatics Ammonium Chloride).

  1. Setup: Fill your tank, add dechlorinator (Seachem Prime), and turn on your filter and heater (set to 80°F/26°C to speed up bacteria growth during cycling only).
  2. Dose Ammonia: Add liquid ammonia until your test kit reads 2.0 ppm.
  3. Test Daily: Test for Ammonia and Nitrite every 24 hours.
  4. The Spike: After 1-2 weeks, Ammonia will start dropping, and Nitrite will spike high. This means the first bacteria colony is growing.
  5. Re-dose: Whenever Ammonia drops below 0.5 ppm, dose it back up to 2.0 ppm to keep feeding the bacteria.
  6. The Second Spike: After 3-5 weeks, Nitrites will start dropping, and Nitrates will appear. The second bacteria colony is establishing.

How Do I Know It's Done?

Your tank is fully cycled when you can dose 2.0 ppm of ammonia, and exactly 24 hours later, your test results show: 0 Ammonia, 0 Nitrite, and some Nitrates. Once this happens, do a large (80%) water change to lower the nitrates, turn off the heater, let the water cool to 60-64°F, and you are ready for your axolotl!