Part 3: Start Safely (Cycling Made Simple) + When to Add Fish

  • 5 min

  1. A new tank needs time to become stable. Don’t worry — you don’t need to be “pro.” Just follow this simple plan.

What is “Cycling”?

  • Cycling means growing the good bacteria in your filter.

    These bacteria help handle fish waste, so your water stays safe.

    No bacteria = water can turn unsafe fast.
    Enough bacteria = tank becomes stable and easy.

The 2 Safe Ways to Start (Choose 1)

Option A (Best & easiest): Cycle first, then add fish

This is the safest route for beginners.

Simple steps:

  1. Set up tank (water + anti-chlorine)
  2. Turn on filter 24/7
  3. Add beneficial bacteria bottle (as directed)
  4. Let it run and “mature” for a short period
  5. Test the water before adding fish

✅ Less stress
✅ Fewer fish problems
✅ More success

Option B (If you really want fish earlier): Add fish slowly (small amount only)

If you add fish too fast in a new tank, the tank can’t “handle” the waste yet.

Safe rule:
Start with a small number of hardy fish, not a full tank.

✅ Add few fish first
✅ Monitor water
✅ Slowly increase over time

How Long Should a New Tank Run Before Fish?

For a smoother start:

  • Recommended: about 2–4 weeks

With bacteria bottle + proper filter running, many tanks start more smoothly — but still don’t rush to add too many fish.

When is it Safe to Add Fish?

✅ Safe signs

  • Filter has been running daily (24/7)
  • You are using anti-chlorine correctly
  • You added beneficial bacteria consistently
  • Water looks clear and doesn’t smell “bad”
  • Your test kit shows the water is in a safe range

Best simple test kit focus:

  • Ammonia, 0 ppm
  • Nitrite 0 ppm

If these are not okay, wait and continue the steps below.

The #1 Beginner Mistake (Avoid this)

❌ Adding too many fish too fast

Even if the tank looks clear, the water can still be unsafe.

Simple rule:
Add fish slowly. Your tank will stay easy.

Best Beginner Fish to Start With (Hardy + calm)

  • Platies
  • Guppies
  • Mollies
  • Harlequin Rasboras

If you want a single fish tank:

  • 1 male Betta (gentle flow + hiding spots)

Quick “Do & Don’t” for Success

✅ DO

  • Keep filter on 24/7
  • Use anti-chlorine every time
  • Feed small amounts
  • Add fish slowly

❌ DON’T

  • Wash filter media under tap water
  • Overfeed (leftover food = water problem fast)
  • Add a full tank of fish on day 1

Beginner “Week-by-Week” Plan

  1. Week 1: Set up & build the base

    • Anti-chlorine every time you add water
    • Filter on 24/7
    • Add beneficial bacteria (follow bottle)
    • Light: keep it simple (4–6 hours/day)

    Week 2: Keep it stable

    • Continue beneficial bacteria
    • Do small water changes if needed
    • Keep feeding low if you already have fish (don’t overfeed)

    Week 3–4: Start adding fish (slowly)

    • Add fish in small batches
    • Wait a few days to 1 week between adding more fish
    • Keep checking water

If you tell our That Aquarium staff what you’re unsure of, we’ll be sure to help wherever we can!

🐡 Puffed up with knowledge? Give us a like and keep floating along!

👉 Next Up: We’ll go over some maintenance basics to keep your tank clean and healthy!

Author: Kelvin Phua

Illustrator(s): Rong Sheng

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