Seachem Stability 500 mL — Nitrifying bacteria for aquariums

Seachem Stability 500 mL is the leading solution for quickly establishing a functional biological cycle in a new marine or freshwater aquarium. Its patented formula contains a synergistic blend of aerobic, anaerobic, and facultative bacteria in spore form—immediately active upon introduction into the aquarium—that facilitate the breakdown of organic waste, ammonia, nitrites, and nitrates. Stability prevents new aquarium syndrome, the leading cause of fish mortality in captivity.

The 500 mL format is the choice of aquarists who maintain one or more large reef systems, who make frequent additions of specimens, or who want a sufficient reserve to deal with biological emergencies without ever running out of product at the wrong time.

Why Stability Spore Bacteria Are Superior

Most recycling products on the market contain active bacteria that require refrigeration to survive and whose viability declines rapidly after opening. Seachem Stability uses a radically different and more effective approach: its bacteria exist in a spore state —alive but metabolically dormant. In this state, they withstand extreme temperatures, require no food to survive, and maintain an exceptional shelf life of 6 years without refrigeration.

Upon introduction into the aquarium, dilution in water instantly activates the spores, which begin to colonize available surfaces—filter, substrate, live rock—within the first 24 hours. There is no rehydration delay and no loss of effectiveness due to transport or storage at room temperature.

The Nitrogen Cycle — Why Stability Is Essential

In any aquarium, the organic waste produced by fish, corals, and uneaten food generates ammonia—a highly toxic compound even at very low concentrations. Without an established bacterial population, this ammonia quickly accumulates to levels lethal to your fish.

The natural nitrogen cycle transforms ammonia into nitrites via the bacteria Nitrosomonas and Nitrosospira , and then nitrites into nitrates via Nitrospira —much less harmful and easily controlled by water changes. Without intervention, this process naturally takes 4 to 8 weeks. Stability dramatically accelerates this timeframe by directly inoculating your filter with massive concentrations of these beneficial bacteria.

Unlike competing products whose bacteria require very specific temperature, pH, and organic load conditions to survive, Stability's bacterial strains function within a very wide range of conditions. While other bacteria collapse under high organic loads, Stability becomes even more effective.

When to Use Seachem Stability 500 mL

Cycling a new aquarium

This is Stability's primary use. From day one, dose generously and maintain the treatment for 7 consecutive days. Fish and other aquatic specimens can be introduced at any time during the dosing period—Stability is completely harmless to all aquatic life, and it is virtually impossible to overdose. When cycling without fish, add a pinch of food daily to provide a source of ammonia for the developing bacteria.

Added new specimens

Each significant introduction of new fish or corals suddenly increases the biomass and organic load of your system. A dose of Stability with each addition prepares your biological filter to absorb this increase without causing an ammonia or nitrite spike that would stress both existing and new specimens.

After drug treatment

Antibiotics and antiparasitics used in quarantine tanks or for emergency treatment destroy beneficial nitrifying bacteria along with pathogens. Turn off UV and ozone during treatment, then dose Stability for 7 consecutive days to quickly replenish your biological filter and avoid a post-treatment mini-cycle that is harmful to your recovering specimens.

Regular maintenance of the biofilter

A monthly dose of Stability keeps your filter's bacterial populations at peak efficiency, strengthening your system's resilience to accidental organic overloads — unexpected mortality, overfeeding, temporary filtration failure.

Biological emergency

Biological crash following a prolonged power outage, accidental overheating, or mass specimen die-off — Stability is the first tool to use in a crisis. Combine with Seachem Prime to chemically detoxify ammonia while bacteria biologically recover.

Seachem Official Usage Protocol

• Shake well before use
• Turn off UV and ozone — for the entire 7-day cycle, or at least 24 hours for maintenance additions
• Day 1 — new aquarium: 5 mL (1 capful) per 40 litres
• Days 2 to 7: 5 mL per 80 liters, daily
• Maintenance: 5 mL per 80 litres, once a month, with each water change, when adding new specimens, or during medication treatment.
• Shelf life: 6 years — no refrigeration required

Yield of the 500 mL format

• 200-liter aquarium cycling: one bottle fully covers the 7-day protocol plus several months of maintenance
• Monthly maintenance for a 400-liter aquarium: approximately 8 doses — enough for over 8 months of use
• Multiple emergencies: sufficient reserve for several consecutive interventions without stockouts