Seachem Stability

Seachem Stability is a bottled bacteria product for starting the biological filter in a new aquarium. It’s made for both freshwater and marine tanks. Seachem describes it as a blend of aerobic, anaerobic and facultative bacteria that break down waste, ammonia, nitrite and nitrate, which is the job a mature biofilter does.

Why new tanks need help

A new tank has no colony of beneficial bacteria yet. Fish waste turns into ammonia, and without bacteria to process it, ammonia and then nitrite build up. That’s “new tank syndrome,” which Seachem calls the top cause of fish deaths. Adding bacteria helps the colony form sooner.

How to dose it

• Shake the bottle well, and turn off any UV sterilizer or ozone while dosing.
• Day 1: 1 capful (5 mL) per 10 US gallons.
• Next 7 days: 1 capful per 20 US gallons, every day.

Seachem says fish can go in at any time, as long as you keep dosing for the full 7 days. Add fish gradually, though, and watch ammonia and nitrite. A liquid kit like the API Freshwater Master Test Kit shows how the cycle is going. Dechlorinate tap water before adding it, too. Seachem Prime pairs naturally with Stability.

Beyond the first week

Stability is also useful after events that set the biofilter back, such as a big water change, new filter media, medication, or adding a lot of fish at once. Seachem notes that its bacteria keep working when other bacteria die off, for example after an unnoticed death in the tank.

Bottle size

This page covers the 500 mL (16.9 fl oz) bottle. At the daily dose of 1 capful per 20 gallons, it lasts a long time on small and mid-size tanks.

Who should look elsewhere

If you’d rather cycle without fish using an ammonia source, a product like Fritz Fishless Fuel is built for that method. You can use Stability alongside it.