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Axolotl Care · Essential Guide
What Your Pet Shop Didn't Tell You About Setting Up an Axolotl Tank
Thousands of axolotls are slowly being poisoned in brand new tanks right now. Their owners have no idea. Here is what is actually happening — and how to fix it.
Quick Answer
Fishless cycling means building a colony of beneficial bacteria in your filter before adding your axolotl. Dose your tank to 4ppm ammonia, test daily, and wait for both ammonia and nitrite to drop to zero within 24 hours on three consecutive days. The process takes 4 to 10 weeks. Never add your axolotl to an uncycled tank.
Jump to a section What is cycling? The nitrogen cycle Symptoms Emergency steps How to fishless cycle Water parameters FAQ
The thing no one tells you when you buy an axolotl
You bought an axolotl. You set up the tank, filled it with water, maybe let it sit for a day or two, and added your new pet. Exactly what the pet shop told you to do — if they told you anything at all.
Here is the problem. That tank is not ready. The water looks clean. It smells fine. But it is slowly building up a level of toxic ammonia that your axolotl's body cannot handle — and without a cycled tank, there is nothing in that water to break it down.
This is not a rare edge case. This is what happens to the majority of axolotls sold in pet shops across the UK. The staff either do not know about cycling, do not have time to explain it, or assume you already know. Most new owners do not find out until their axolotl starts showing symptoms — by which point real damage may already be done.
This page exists to give you what you should have been told on day one.
What does "cycling a tank" actually mean?
Every time your axolotl breathes, eats, and produces waste, it releases ammonia into the water. Ammonia is highly toxic. In an uncycled tank, it has nowhere to go — it just builds up.
Cycling a tank means establishing a colony of beneficial bacteria in your filter that can process that ammonia before it reaches dangerous levels. These bacteria convert ammonia into nitrite — also toxic — and then a second group converts nitrite into nitrate, which is relatively harmless at low levels and removed through regular water changes.
This process — the nitrogen cycle — happens naturally. But it takes time. Usually four to eight weeks. And until it is fully established, your tank water is not safe for your axolotl.
Fishless cycling means going through this process before adding your axolotl — using ammonia to feed the bacteria without putting a living animal in harm's way. It is the right way to do it. And it is what this guide is going to walk you through.
The nitrogen cycle, simply explained
Axolotl waste produces
Ammonia (NH₃)
→
Bacteria convert to
Nitrite (NO₂)
→
Bacteria convert to
Nitrate (NO₃)
→
Removed by
Water Changes
Ammonia and nitrite are both acutely toxic to axolotls. Nitrate is tolerable at low levels — under 20ppm is your target — and kept in check with regular partial water changes. The goal of cycling is to have enough bacteria in your filter to process ammonia and nitrite as fast as they are produced.
In a brand new tank, those bacteria do not exist yet. They take weeks to colonise your filter media. That is the window during which your axolotl is at serious risk.
Symptoms of an uncycled or poorly cycled tank
These are the signs that ammonia or nitrite is building up in your water. If your axolotl is showing any of these, test your water immediately.
Refusing to eat
Unexplained weight loss
Pale or ragged gills
White fluffy fungal growth
Limb deterioration
Lethargy or floating oddly
Important
These symptoms can have other causes — temperature, disease, stress. But if your tank is new or has not been properly cycled, water quality should be the very first thing you check. Test before you treat anything else.
Emergency: your axolotl is already in an uncycled tank
If your axolotl is already in the tank and you suspect the water is the problem, do not wait until you have finished reading this page.
🚨 Emergency steps — do these first
- Test your water. You need an API Master Test Kit — not strips, which are inaccurate. Test for ammonia, nitrite, nitrate, and pH. If you do not have one, get one today.
- Do a 30–50% water change immediately using dechlorinated water at the same temperature as the tank. This dilutes ammonia and buys your axolotl time.
- Do not feed your axolotl while ammonia is elevated. Feeding produces more waste and makes things worse.
- Add a dechlorinator that neutralises ammonia — Seachem Prime will temporarily detoxify ammonia and nitrite, giving you a short window to stabilise the tank.
- Repeat daily water changes of 30–50% until ammonia and nitrite both read zero on two consecutive tests.
- Do not add treatments or medications until you know exactly what the water parameters are.
Once your axolotl is stable, work through the fishless cycling process below to establish your filter bacteria properly. Daily water changes are a sticking plaster — proper cycling is the fix.
How to fishless cycle your axolotl tank
This is the method we recommend for anyone setting up a new tank — or anyone whose tank has not been properly cycled yet. It takes anywhere from four to ten weeks. It requires patience. It is absolutely worth it.
Check your water hardness first
Before you start, check whether your area has hard or soft water using the UK hard water map. Hard water? You are lucky — the process is straightforward. Soft water causes problems during cycling that you need to know about before you begin. If in doubt, get in touch and we can help.
What you will need
- Dr Timms Liquid Ammonia (or Knockout Ammonia) — 1ml per 20L of tank water to reach 4ppm
- NT Labs Aquarium Axo-Safe — dechlorinator, essential for every water change
- API Liquid Freshwater Master Test Kit — liquid tests only, strips are not accurate enough
- Bottled bacteria such as Seachem Stability — optional but can help speed things up
- A heater — optional but recommended (bacteria grow much faster at 28°C)
- Sodium bicarbonate (baking soda) — for managing pH if it drops
1
Set up your tank, dechlorinate, and run the filter
Fill your tank and dechlorinate using NT Labs Axo-Safe following the bottle instructions. If you are using a heater, set it to 28°C — bacteria grow significantly faster in warmer water, which shortens the whole process. Run the filter continuously from this point. Never switch it off during cycling or you will kill the bacteria colonising the media.
2
Dose ammonia to 4ppm
Add Dr Timms ammonia at roughly 1ml per 20L of tank water — so 5ml for a 100L tank. Test after an hour to confirm you are sitting at 4ppm. This level is the nearest equivalent to the waste an axolotl produces, which means your filter has to be strong enough to eliminate it — exactly what you need to prove before adding your animal. Use the ammonia calculator (10% concentration) to get your starting dose right. If you are using bottled bacteria, add it directly into the filter rather than the tank water.
3
Test pH and ammonia daily — and keep pH above 7
Using your API Master Test Kit, test pH and ammonia every single day. Aim to keep pH at 7.6 throughout. If it drops below 7 at any point, add a small spoon of bicarbonate of soda and retest in 30–60 minutes. Repeat until pH is back above 7.6. Low pH stalls the cycle — do not ignore it. It may take 2–5 weeks before you see ammonia starting to come down. That is normal. Keep going.
4
When ammonia starts falling, add nitrite to your daily tests
Once ammonia begins dropping, start testing for nitrite daily as well. Top ammonia back up to 4ppm any time it falls below that. Getting into a daily dosing routine makes it much easier — you will quickly learn exactly how much your tank needs. Keep a simple log if it helps.
5
When nitrite hits 5ppm, reduce ammonia dose to 2ppm
This step is important and often missed. Once nitrites spike to 5ppm, reduce your ammonia dose to keep it at 2ppm rather than 4ppm. Letting nitrites go off the chart at this stage will stall the cycle. Even if ammonia is dropping to 0ppm on its own, keep dosing to 2ppm — the bacteria still need something to feed on.
6
When nitrites start falling, dose ammonia back to 4ppm
Once nitrite begins coming down, increase your ammonia dose back to 4ppm. Continue until both ammonia and nitrite drop to 0ppm within a 24-hour period from your last ammonia dose.
7
Cool the tank down slowly
If you used a heater, turn it off now and let the water cool gradually to 15–18°C. Do not rush this — a rapid temperature drop can shock the bacteria and stall the cycle at the last hurdle. Once at temperature, dose ammonia to 4ppm and test after 24 hours.
8
The 3-day confirmation test
This is how you know the cycle is genuinely complete — not just nearly there.
- Day 1: Did ammonia and nitrite both drop to 0ppm? Yes — dose back to 4ppm. No — go back to step 6.
- Day 2: Same question. Yes — dose back to 4ppm. No — go back to step 6.
- Day 3: Both at 0ppm again? Your tank is cycled. Test your nitrates — they will likely be very high. Dose a small amount of ammonia to keep the bacteria fed, then begin daily 50% water changes (dechlorinating each time with NT Labs Axo-Safe) until nitrates are down to 5–10ppm. At that point, your tank is ready for your axolotl.
Speed up the process with seeding
You can significantly shorten cycling time by adding filter media from an already-cycled tank directly into your filter. Even a small piece of established sponge carries millions of the bacteria you need. Ask in axolotl keeping communities — many experienced keepers will share media. You still need to go through all the steps above, but the timeline can shrink considerably.
Safe water parameters for an axolotl tank
You cannot manage what you cannot measure. Liquid test kits are non-negotiable — strips are not accurate enough. The API Freshwater Master Test Kit covers everything you need. If you are having ongoing pH trouble, the API KH & GH liquid tests are worth adding — they help diagnose why pH is shifting and how to correct it properly.
| Parameter | Safe level | Danger level | Action |
|---|---|---|---|
| Ammonia (NH₃) | 0 ppm | Above 0 ppm | Immediate water change; dechlorinate with NT Labs Axo-Safe |
| Nitrite (NO₂) | 0 ppm | Above 0 ppm | Immediate water change; dechlorinate with NT Labs Axo-Safe |
| Nitrate (NO₃) | 5–20 ppm | Above 20 ppm | Partial water change to dilute |
| pH | 7.4 – 7.6 ideal (7.0–8.0 acceptable) | Below 7.0 | Add small spoon of bicarbonate of soda; retest in 30–60 mins |
| Temperature | 15°C – 18°C | Above 20°C | Cooling fan, frozen water bottles, tank chiller |
Test weekly once your tank is established. If anything reads outside the safe zone, switch to daily testing until it resolves. Water problems are invisible until they are serious — do not wait for symptoms.
Frequently Asked Questions
How long does fishless cycling take?
Anywhere from four to ten weeks from scratch depending on your water hardness, temperature during cycling, and whether you use seeding media. With a heater at 28°C and established filter media it can be considerably faster. Without either, expect the longer end of that range. Do not rush it — an incomplete cycle is worse than a longer wait.
Can I add my axolotl before the cycle is complete?
Only if you have no choice and are prepared to do daily 30–50% water changes to keep ammonia and nitrite from reaching dangerous levels. Dechlorinate every change with NT Labs Axo-Safe. It is stressful for the animal and exhausting for you. The right answer is to wait.
Why does my pH keep dropping during cycling?
This is common, especially in soft water areas. The cycling process itself can drive pH down. Add a small spoonful of bicarbonate soda, wait 30–60 minutes, and retest. Repeat until the pH returns to 7.6. If you are in a soft water area and struggling, get in touch — it gets complicated, and there are specific steps to follow.
My ammonia won't drop to zero — what's wrong?
Either the bacterial colony is not large enough yet, your pH has dropped below 7 (which stalls bacterial activity — check it), the temperature is too low, or you have been doing large water changes and removing the ammonia before the bacteria can process it. Check pH first, then temperature, then keep the filter running and be patient.
My nitrites went off the chart — what do I do?
Reduce your ammonia dose to 2ppm and hold it there. Very high nitrite stalls the cycle. Do not do large water changes to try to bring it down — just reduce the ammonia input and let the bacteria catch up. This is exactly why you drop to 2 ppm when nitrite hits 5 ppm during step 5.
Do I need to do water changes during cycling?
Generally no — the ammonia and nitrite are feeding your developing bacteria. The exception is if nitrite rises significantly above 5 ppm for several days, at which point it can stall things. Otherwise resist the urge. Patience is the main ingredient here.
My tank was cycled but now ammonia is spiking again — why?
Most common causes: the filter was switched off even briefly, filter media was rinsed in tap water rather than tank water (chlorine kills the bacteria instantly — always use tank water to rinse media), too many new animals added at once, or something has died and is decomposing in the tank. Test, do a water change with Axo-Safe, and find the cause.
Do I need to dechlorinate tap water every time?
Every single time, without exception. Chlorine and chloramine kill your filter bacteria instantly. NT Labs Axo-Safe is specifically formulated for axolotls and treats tap water safely before each water change.
What temperature should my axolotl tank be once cycling is done?
15–18°C is the target range for a cycled axolotl tank. Cool the tank down slowly after cycling — a rapid temperature drop can shock the bacteria. Above 20°C axolotls become stressed and stop eating. Above 22°C it is a serious health risk. UK summers can be problematic — a fan over the tank surface or a purpose-built aquarium chiller are your options.
Ready to sort your axolotl's diet too?
Once your tank is cycled and your axolotl is settled, the next question is feeding. Our complete feeding guide covers every life stage — from hatchling to adult.
Read the feeding guide →