If you're new to fishkeeping, there's one critical process you must understand before adding fish to your tank: the nitrogen cycle. It’s the foundation of a healthy, stable aquarium. Without it, even the hardiest guppies won't thrive.
What Is the Nitrogen Cycle?
The nitrogen cycle is nature’s way of breaking down waste in your aquarium. Fish produce waste, uneaten food decays, and plants shed debris — all of this releases ammonia (NH₃), which is toxic to fish, even in small amounts.
Here’s how the cycle works:
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Ammonia (NH₃) is produced from fish waste and decay.
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Beneficial bacteria convert ammonia into nitrite (NO₂⁻), which is also toxic.
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Another set of bacteria convert nitrite into nitrate (NO₃⁻), which is far less harmful in low amounts.
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Regular water changes help remove excess nitrate.
This entire process usually takes 4–6 weeks in a brand-new tank. During this time, the tank is cycling — building up colonies of beneficial bacteria in your filter and substrate.
How to Properly Start a New Aquarium
1. Choose Your Setup Wisely
Start with a tank size of at least 10 gallons. Nano tanks are great, but small volumes mean water parameters can swing fast. Use a reliable filter and consider a heater if your room drops below 72°F.
2. Use a Dechlorinator
Tap water contains chlorine or chloramine, which kills the good bacteria you're trying to grow. Always treat your water with a dechlorinator like Seachem Prime before adding it to the tank.
3. Cycle Your Tank Before Adding Fish
There are two ways to cycle your tank:
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Fishless Cycling (Recommended)
Add a source of ammonia (like bottled pure ammonia or fish food). Test daily with a liquid test kit. Ammonia will spike, then drop as nitrite rises. Eventually, both will drop and nitrate will rise. That’s when your tank is cycled. -
Fish-In Cycling (Only if Necessary)
Use very hardy fish like guppies, feed lightly, and test daily. Perform frequent water changes to keep ammonia and nitrite low. This is more stressful for the fish and should only be done carefully.
4. Test Your Water Often
Invest in a liquid test kit like the API Freshwater Master Kit. Track ammonia, nitrite, and nitrate levels regularly. Your tank is fully cycled when:
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Ammonia = 0 ppm
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Nitrite = 0 ppm
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Nitrate = 10–40 ppm
5. Add Fish Slowly
Once your tank is cycled, add fish gradually. Adding too many fish at once can overwhelm the bacteria. Start with a few and give the system time to adjust.
Final Thoughts from The Guppy Father
Don’t rush the process — the best guppy tanks are built on patience. A properly cycled tank means healthier fish, fewer problems, and a much more enjoyable hobby. At The Guppy Father, every guppy is raised in fully cycled tanks using this exact method — so you can trust that your new arrivals come from clean, stable water.