How to Tank Cycling for Reef Keeping - Step by Step
Step-by-step guide to Tank Cycling for Reef Keeping. Includes time estimates, tips, and common mistakes to avoid.
Cycling a reef tank is the process of building a stable population of beneficial bacteria that convert toxic ammonia into nitrite and then nitrate before fish, corals, or invertebrates are added. A careful, measured cycle helps prevent livestock loss, limits ugly early-stage algae outbreaks, and gives your reef a much stronger start.
Prerequisites
- -Aquarium, stand, sump or filtration system, and return pump fully installed and leak tested
- -RODI water and a quality reef salt mix to prepare saltwater at 1.025-1.026 SG
- -Refractometer or calibrated digital salinity meter
- -Heater and thermometer to maintain 77-79 F
- -Flow pumps or wavemakers for internal circulation
- -Dry rock, live rock, or a combination, plus rinsed reef-safe sand if using a sand bed
- -Reliable test kits for ammonia, nitrite, nitrate, pH, alkalinity, and phosphate
- -A bottled nitrifying bacteria product rated for saltwater systems
- -A measured ammonia source such as ammonium chloride or a small amount of fish food
- -Basic understanding of the nitrogen cycle and how to interpret ppm-based test results
Fill the tank and sump with RODI water, add reef salt, and circulate it for at least 24 hours before beginning the cycle. Adjust salinity to 1.025-1.026 SG and stabilize temperature at 77-79 F. Confirm pH is roughly 7.9-8.3 and ensure all pumps, heater, and overflow are running correctly.
Tips
- +Mix salt in a brute container or reservoir first if possible, then transfer to the display for more consistent salinity
- +Calibrate your refractometer with calibration fluid, not freshwater
Common Mistakes
- -Starting the cycle with unstable salinity or temperature
- -Using untreated tap water, which can introduce phosphate, silicate, and other contaminants
Pro Tips
- *If you start with true ocean-cultured live rock, inspect carefully for pests like aiptasia, mantis shrimp, and nuisance crabs before placing it in the display
- *For dry rock systems, consider ghost feeding lightly after the cycle if livestock will not be added right away, so the bacterial population does not shrink
- *Keep alkalinity in a reasonable range during startup, around 7.5-9.0 dKH, because extreme values can add unnecessary instability while the tank matures
- *Do not rely on nitrate alone to judge cycle completion, because nitrate can appear before the tank can consistently process a fresh ammonia input
- *When the cycle is complete, add livestock in stages at least 1-2 weeks apart so the biological filter can scale up safely with each increase in bioload
Keep a clean backup log for test day.
The Printable Reef Logbook gives you water testing, dosing, maintenance, and livestock worksheets you can print or save as a PDF.