What is nitrate in aquariums?
Nitrate (NO₃⁻) is the end product of the nitrogen cycle, formed when nitrite is converted by beneficial bacteria.
Why nitrate matters
While less toxic than ammonia or nitrite, high nitrate can:
- Stress fish
- Promote algae blooms
- Hinder plant growth
Safe levels
- Freshwater aquariums: <40 ppm
- Planted tanks: 10–20 ppm for optimal growth
- Marine aquariums: <20 ppm
Nitrate in the nitrogen cycle
Nitrate is the final and least toxic stage of the nitrogen cycle, but it can still build up and stress fish if not controlled. It is reduced through water changes, plant uptake, and denitrifying filtration.
How to manage nitrate
- Regular partial water changes
- Avoid overfeeding and overstocking
- Use live plants to absorb nitrates
- Consider nitrate-removing filtration media if needed
Nitrate is a key indicator of aquarium health and overall water quality.