How to Cycle a Reef Tank: The Complete Brisbane Guide to the Nitrogen Cycle
Posted by Gallery Aquatica on
Every new reef tank in Brisbane goes through the same invisible process before it can hold a single fish. Bacteria have to build up inside your rock, sand and filter media to process fish waste. Skip this step or rush it, and you'll watch ammonia spike, corals bleach, and fish gasp at the surface within days. This guide walks through exactly how the cycle works, how long it actually takes with our local tap water and climate, and which test kits will tell you the truth rather than a guess.
Table of Contents
- What the nitrogen cycle actually does
- Live rock vs dry rock cycling
- Step by step: cycling a reef tank in Brisbane
- How long does a reef tank take to cycle
- Testing methods compared
- Good, better, best cycling setups
- FAQ
What the nitrogen cycle actually does
Fish, coral and leftover food produce ammonia. Ammonia is toxic even at tiny concentrations, so the tank needs bacteria that convert it into nitrite, then a second group of bacteria that convert nitrite into nitrate. Nitrate is far less harmful and gets exported through water changes or a refugium. This whole chain is called the nitrogen cycle, and it has to establish itself on hard surfaces inside the tank, mainly the rock, sand bed and filter media, before you can safely stock livestock.
In a brand new setup there are no bacteria colonies at all. You're building an entire ecosystem from nothing, using Brisbane tap water (which is chloraminated, by the way, so it needs conditioning or an RO/DI unit before use) and whatever rock or sand you choose to start with.
Live rock vs dry rock cycling
This is the first fork in the road for anyone learning how to cycle a reef tank. Live rock arrives already colonised with bacteria, plus hitchhiking pods, worms and sometimes coralline algae. It shortens the cycle considerably, often to two or three weeks, but it carries a higher risk of pests like Aiptasia or bristle worms hitching a ride, and it costs more per kilo.
Dry rock is cheaper, pest free, and lets you aquascape without rushing, but it starts completely sterile. You're relying entirely on bottled bacteria and an ammonia source to seed it, which usually stretches the process to four to eight weeks. Most Brisbane reefers now go with a dry rock base plus a small amount of live rock or live sand mixed in, getting some of the seeding benefit without the full pest risk.
Step by step: cycling a reef tank in Brisbane
1. Prepare your water
Use RO/DI water or well conditioned tap water mixed with a reef salt to the correct specific gravity, generally 1.025 to 1.026. Brisbane Council water quality is decent but chloramine and phosphate levels vary through the year, so a decent test kit from our test kits range at setup is worth the ten minutes it takes.
2. Add your rock and sand
Arrange your aquascape now rather than later. Moving rock once bacteria have established disturbs the biofilm and can restart parts of the cycle.
3. Introduce an ammonia source
Dose pure ammonia to around 2 to 4 ppm, or use a small piece of raw prawn, or dose a bacterial starter with a food source built in. Products like those in our Dr Tim's range are a reliable way to seed bacteria quickly without guessing dosages.
4. Test daily
Track ammonia, nitrite and nitrate every day or two. You'll see ammonia climb first, then drop as nitrite rises, then nitrite drops as nitrate rises. Once ammonia and nitrite both read zero and nitrate is present, the cycle is functionally complete.
5. Confirm with a second ammonia dose
Don't stop at one clean reading. Dose ammonia again to 2 ppm and see how fast the tank processes it. If ammonia and nitrite both clear within 24 hours, your bacteria colony is strong enough to handle a fish's bioload.
6. Do a large water change before stocking
Nitrate can build up quite high during a cycle. A 30 to 50 percent water change before adding your first fish or coral resets nitrate to a safe starting point.
How long does a reef tank take to cycle
There's no single answer, but here's what is typical across most setups.
| Setup type | Typical cycle time | Notes |
|---|---|---|
| Fully cured live rock | 2 to 3 weeks | Fastest option, higher pest risk |
| Dry rock plus live sand | 3 to 5 weeks | Good balance of speed and pest control |
| Fully dry rock and sand | 4 to 8 weeks | Cleanest start, needs a bacteria starter product |
| Established tank, new frag added | No cycle needed | Mini cycle possible if bioload jumps sharply |
Winter in Brisbane tends to slow bacterial activity slightly if your tank temperature drifts below the mid twenties, so keeping a heater running steadily through July helps the cycle move along at the rate the table suggests rather than stalling out.
Testing methods compared
Cheap test kits will get you through a basic cycle, but they're not always precise enough to catch a false zero on ammonia or nitrite, especially once corals are in and you want tighter control over trace elements too. Here's how the main options stack up.
| Method | Best for | Approx cost |
|---|---|---|
| Hobbyist liquid test kits (API, Salifert) | Confirming basic cycle completion | $20 to $60 |
| ICP-style lab testing (Triton) | Detailed water report once cycled, ongoing reef chemistry | Subscription based, from $0 for the app with test kit purchase |
| Continuous digital monitoring (Apex Trident) | Set and forget tracking of alkalinity, calcium, magnesium and more | $1499 |
Most people cycling their first tank only need a solid liquid kit from our test kit collection. Once the tank is stocked and you're chasing stability for SPS corals, something like the APEX TRIDENT - WATER ANALYZER ($1499, /products/apex-trident-water-analyzer) or a TRITON MYTE SUBSCRIPTION (0 AUD, /products/triton-myte-subscription) gives you a much clearer long term picture than dip tests alone.
Good, better, best cycling setups
Good
Dry rock, dry sand, a bacteria starter, and a basic liquid test kit. Slower, but budget friendly and low pest risk. Expect five to eight weeks before stocking.
Better
Dry rock plus a bag of live sand, a proper bacteria starter dosed to schedule, and weekly testing with a mid range kit. Add a supplement like MICROPLEX ($55, /products/microplex) once the tank is cycled to support early coral growth and biological filtration as you stock up.
Best
Cured live rock or a mix with dry rock, a full liquid test kit range from launch, and a Triton or Trident setup running from day one so you have baseline data before your first fish goes in. This is the setup many advanced reef keepers run because it removes guesswork entirely.
FAQ
Can I put fish in during the cycle?
No. Ammonia and nitrite are both toxic to fish even at low levels. Wait until both read zero on two consecutive tests taken a few days apart.
Do I need a clownfish to start the cycle like the old days?
No, and we'd strongly discourage it. Fishless cycling using pure ammonia or a bacterial starter is more reliable and doesn't put a fish through unnecessary stress.
Why is my ammonia stuck and not dropping?
Check your tank temperature and salinity are stable, and confirm your test kit reagents aren't expired. Cold water in a Brisbane winter can slow bacterial activity, so aim for 24 to 26 degrees Celsius during the cycle.
Can I speed up a reef tank cycle?
Bottled bacteria products and a small piece of mature live rock or filter media borrowed from an established tank both help. Skipping steps to save time almost always backfires later.
How do I know the cycle is really finished, not just paused?
Dose ammonia to 2 ppm again after your first clean reading. If it's gone within 24 hours along with any nitrite, the bacterial colony is established and stable.
Prices mentioned in this article are accurate at the time of publishing and are subject to change. Please check the relevant product page for the current price before purchasing.