Are water changes necessary during cycling?
Written by
Hoang Long
Reviewed by
Prof. Henry Webster, Ph.D.Water changes during aquarium cycling should be carefully weighed out as they remove the ammonia that feeds the developing colonies of bacteria. Premature water changes can stall the cycling process, while failing to perform water changes when necessary can lead to toxic conditions in the aquarium. I have developed protocols for effecting these changes, which have been honed over the years of aquarium consulting I have engaged in.
Emergency Interventions
- Perform 25-30% change when ammonia exceeds 5 ppm
- Do 50% change if nitrite surpasses 5 ppm
- Always use dechlorinated water matching temperature
Prohibited Circumstances
- Avoid changes when ammonia is between 1-4 ppm
- Never change water during bacterial bloom phases
- Skip changes if nitrite is present but under 1 ppm
Post-Change Procedures
- Redose ammonia to 2 ppm after emergency changes
- Add bacterial supplements to compensate for dilution
- Retest parameters within 2 hours
Maintain the ammonia level between 2-4 ppm during normal cycling, and refrain from changing the water. These levels will provide food for the bacteria without becoming toxic. You will find it hard to resist the urge to change the water if it becomes cloudy during the blooming stages of bacterial growth. These cloudy times indicate biological activity, and these periods will clear on their own.
For emergencies, use dechlorinated water at the same temperature to stock bacteria. Add ammonia back to 2 ppm immediately after changing the water. Dose bacterial starters in filter media to resupply colonies. This protocol saved several client tanks from crashes during the last season.
Monitor water parameters very strictly using liquid test kits, not strips. Daily tests for ammonia and nitrite levels are required during critical phases of the process. Keep all information logged clearly to define what constitutes emergencies and what are the natural fluctuations of the cycle. The discipline in doing this daily removes unnecessary hardships in cycling your tanks.
Once the cycling is complete, perform a substantial water change of 50-70% before adding the fish. This helps to eliminate the excess nitrates accumulated during the cycling period. After the fish are added, regular water changes of 20-30% weekly will help maintain good water quality. This is the transition period from the cycling to the maintenance phase.
Read the full article: Aquarium Cycling Process: Essential Beginner's Guide
