Freshwater Aquarium Cycling Explained
7 min read · TankBase
The cycling process is identical in freshwater and saltwater — same bacteria, same chemistry. The difference is that tropical tanks are usually softer, slightly acidic, and full of plants that change how nitrogen behaves.
Fishless cycling (the right way)
Set the tank up fully: substrate, plants, heater at 26 °C, filter running.
Dose pure ammonia to 2 ppm. Add a bottled bacteria starter such as Tetra SafeStart, Seachem Stability or API Quick Start.
Test ammonia and nitrite daily. Top up ammonia back to 2 ppm every time it drops to zero.
When ammonia and nitrite both clear within 24 hours of a 2 ppm dose, do a 50% water change and stock lightly.
Why fish-in cycling is risky
Putting hardy fish in a brand-new tank works — but it exposes them to weeks of low-level ammonia and nitrite, which damages gills and shortens lifespan. If you must, do daily 25% water changes and test every morning.
Plants accelerate everything
Heavily planted tanks consume ammonia directly. A well-planted 60L can be safely lightly stocked from day one — but you still need to test daily for the first three weeks.
Target parameters
Ammonia: 0. Nitrite: 0. Nitrate: under 20 ppm.
pH: 6.8–7.6 for most community fish.
Temperature: 24–26 °C.
GH 4–8 dGH, KH 3–6 dKH for typical tropicals. Discus and shrimp need narrower ranges.
Track these parameters automatically
TankBase Tank Log charts every reading you take and flags anything out of range — free to try.
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