In Part 1 of this series, we covered what the nitrogen cycle is, why new tanks don't have one, and the predictable week-by-week sequence of New Tank Syndrome that kills fish in uncycled aquariums. If you came away understanding that cycling is non-negotiable and that clear water is not the same as safe water, you're in the right place to take the next step.
Now the practical question: how do you actually cycle a new tank?
There are three methods, each with different timelines, different requirements, and different trade-offs. The right one for you depends on whether you already have fish in the tank, whether you have access to an established aquarium, and how quickly you need the tank ready.
Before Any Cycling Method: The Non-Negotiables
Regardless of which cycling method you choose, three things must be in place from day one:
The filter must run continuously. Beneficial bacteria are biofilm formers; they colonise filter media surfaces, not free water. The filter must run 24 hours a day throughout the entire cycling process. Turning it off overnight begins killing the developing colony within hours, as these bacteria are aerobic and need continuous oxygenated water flow to survive.
The water must be dechlorinated. Chlorine and chloramine kill bacteria. Every drop of water added to the tank for the initial fill and for every water change during cycling must be treated with a water conditioner before it contacts the developing bacterial colony. Sunken Garden Anti-Chlorine is the conditioner of choice: it instantly neutralises chlorine and chloramine, binds heavy metals, and adds 15 strains of beneficial bacteria with every dose — reinforcing the colony you're trying to build.
The temperature must be stable and warm. Nitrifying bacteria grow fastest at 26–28°C. A heater set to 26–27°C and left running throughout cycling optimises bacterial growth rate. Below 20°C, bacterial growth slows significantly. Above 30°C, it also slows. Stable and warm is what the bacteria need.
Method 1: Fishless Cycling. The Recommended Approach
Timeline: 3–5 weeks (2–3 weeks with Sunken Garden Good Bacteria) Fish at risk: None Difficulty: Beginner
Fishless cycling is the approach every experienced aquarist recommends and for good reason. It establishes the full bacterial colony before any fish enter the tank, meaning your fish arrive in water that's already biologically stable and ready to handle their waste.
The principle is simple: you provide an ammonia source to feed the developing bacteria, let the colony grow in response, and add fish only once the cycle is confirmed complete by water testing.
Step-by-Step: Fishless Cycling
Step 1: Fill and set up the tank completely. Fill with tap water treated with Sunken Garden Anti-Chlorine. Install and run the filter, set the heater to 26–27°C, add substrate and hardscape if using. Run everything exactly as you would for a fully stocked tank; the bacteria need warm, oxygenated, moving water from day one.
Step 2: Choose and add your ammonia source. You need ammonia in the water for the bacteria to feed on. Three options work well in Indian conditions:
- A small piece of raw prawn from the kitchen placed in a mesh bag in the tank. As it decomposes over several days, it releases ammonia. Remove and replace when fully decomposed. Widely available, free, and effective, the most practical option for most Indian hobbyists.
- Pure ammonia solution (ammonium hydroxide from a pharmacy or hardware shop must be pure, no surfactants or additives): dose to achieve 2–4 ppm, confirmed with a test kit. The most precise method, but requires sourcing pure ammonia.
- A small daily pinch of fish food left to decompose. The slowest method, but works without any additional sourcing.
Step 3: Dose Sunken Garden Good Bacteria on Day 1. Add 1ml per 10 litres of tank volume directly into the filter intake, with the filter running. This immediately seeds the filter media and tank surfaces with live denitrifying bacterial strains, giving the colony a head start rather than waiting for bacteria to arrive naturally. Repeat daily for the first week. We'll cover exactly how Good Bacteria works in Part 3 of this series.
Step 4: Test the water every two to three days. Use TCWS Water Test Strips to monitor ammonia, nitrite, and nitrate. You're watching for a specific sequence:
- Ammonia rises, then peaks and begins to fall → Nitrosomonas bacteria are establishing
- Nitrite rises as ammonia falls, peaks, then begins to fall → Nitrobacter bacteria are establishing
- Both ammonia and nitrite reach 0 ppm, nitrate is detectable → Cycle complete
Step 5: The 24-hour ammonia test. Before declaring the cycle complete, add a final dose of your ammonia source and test 24 hours later. If ammonia returns to 0 ppm within 24 hours, the colony is large enough and active enough to handle your planned fish stock. If ammonia is still detectable after 24 hours, the colony needs more time.
Step 6: 50% water change, then add fish gradually. Once the cycle is confirmed, do a 50% water change to dilute accumulated nitrate. Then add your fish in stages: one-third of the planned stock to start, wait two weeks, add the next third, wait two weeks, complete the stocking. This gives the bacterial colony time to grow in proportion with the increasing waste load.
Method 2: Fish-In Cycling. When Fish Are Already in the Tank
Timeline: 4–6 weeks (3–4 weeks with Sunken Garden Good Bacteria) Fish at risk: Yes, requires active management Difficulty: Intermediate
Sometimes fish arrive before cycling is complete: an impulse purchase, a gift, or simply starting the hobby without knowing about cycling. Fish-in cycling is not the ideal approach, but it can be done humanely with the right management. The goal is to protect the fish from ammonia and nitrite toxicity while the cycle develops around them.
Step-by-Step: Fish-In Cycling
Dose Sunken Garden Good Bacteria immediately; this is the most critical step. 1ml per 10 litres, daily, from day one. The faster the bacterial colony establishes, the shorter the window during which fish face ammonia exposure. Don't wait to dose on the same day the fish go in.
Add Sunken Garden Anti-Chlorine at every water change. Its 15-strain bacterial formula reinforces the developing colony with each dose, compounding the effect of Good Bacteria and helping the cycle establish faster while protecting the water from chlorine-related bacterial die-off.
Test the water every single day. Ammonia and nitrite are your daily vital signs. If ammonia rises above 0.5 ppm or nitrite above 0.25 ppm, conduct an immediate partial water change of 25–30% of tank volume, with dechlorinated, temperature-matched water to dilute the toxin before it reaches damaging concentrations.
Underfeed significantly throughout cycling. Less food means less waste means less ammonia. Feed half your normal amount, ensure everything is consumed within two minutes, and remove any uneaten food promptly. This is the single easiest way to reduce ammonia load while the colony develops.
Never clean the filter during cycling. The bacteria you're trying to grow live in the filter media. Cleaning it during a fish-in cycle removes the colony at its most vulnerable stage. Leave the filter completely alone until after the cycle is confirmed complete by testing.
Don't add more fish until the cycle is done. Every additional fish increases the ammonia load at the worst possible time. Hold off on any new purchases until ammonia and nitrite both read 0 ppm.
Method 3: Seeded Cycling. The Fastest Method
Timeline: 7–14 days (sometimes less with Good Bacteria) Fish at risk: Minimal with careful monitoring Difficulty: Intermediate
Seeded cycling is the fastest approach available, and when done well, it can produce a biologically stable tank in a fraction of the time of other methods. The key is access to an established aquarium.
How Seeding Works
Beneficial bacteria don't just live in water; they colonise surfaces as biofilm. Filter media from an established, healthy tank carries a dense, active population of both Nitrosomonas and Nitrobacter bacteria. Transferring this media to a new tank's filter immediately seeds the new system with a working bacterial colony, bypassing the weeks-long wait for natural colonisation.
Step-by-Step: Seeded Cycling
Step 1: Source established filter media. Options in India:
- Your own established tank: Transfer a handful of ceramic rings, a piece of sponge, or a used filter pad from an established tank's filter to the new tank's filter.
- A trusted friend's tank: Same process; a small amount of their established media seeds your new filter.
- A reputable local fish shop: Many will provide a small piece of used filter sponge on request. Avoid shops where tanks show signs of disease.
The amount matters: a larger transfer of established media means a faster, more robust initial colony. Even a small amount accelerates the cycle meaningfully.
Step 2: Dose Sunken Garden Good Bacteria on setup day. Seeded media provides the starting population; Good Bacteria expands and diversifies it, particularly adding the denitrifying strains that process nitrate all the way to harmless nitrogen gas, which the transferred media alone may not provide in sufficient quantity.
Step 3: Add fish lightly and monitor daily. A well-seeded tank with Good Bacteria dosed on day one can sometimes handle a small initial fish stock within a week, but test daily without exception. Have your water change protocol ready. If ammonia or nitrite climbs above threshold, treat it immediately rather than waiting.
Choosing Between the Three Methods
If you're planning before buying fish: Fishless cycling is the right choice. No fish are at risk, you control the timeline, and the tank is biologically ready before a single fish enters.
If fish are already in the tank: Fish-in cycling with daily Good Bacteria dosing and daily water testing is the responsible approach. It's more demanding but manageable with the right routine.
If you have access to an established tank: Seeded cycling with Good Bacteria gives you the fastest possible result. This is how experienced hobbyists set up new tanks; they're never starting from biological zero.
Regardless of method: Sunken Garden Good Bacteria meaningfully shortens the timeline and supports the developing colony through every approach. In Part 3, we'll look in detail at exactly how it works, why it accelerates cycling specifically, and the dosing protocol for each method.
👉 Continue to Part 3: How Sunken Garden Good Bacteria Accelerates the Cycle →
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Questions about which cycling method suits your situation? Write to us at info@mayurdevaquascaper.com
