Brightwell Aquatics MicroBacter Start XLM Marine Aquarium Cycling Aid, 20L, 15x Concentrated

Brightwell Aquatics MicroBacter Start XLM is a concentrated live-microbe cycling aid for establishing or restoring biological filtration in marine aquariums, with a 15x-strength formula in the 20L size.

• 15x-concentrated blend — supports biological filtration with a concentrated dose of beneficial microbes.
• Usually cycles a tank in 7 days in most cases — helps establish nitrifying bacteria in a new aquarium.
• For marine and brackish aquariums — supports nitrogen-cycle care across both environments.
• Useful after cleaning or medication — helps re-establish bacteria beds affected by these events.
• Shelf-stable for over a year at room temperature — offers a long-lasting formula for aquarium care.

Starting a marine aquarium, adding fish, or recovering from a disruption can affect the bacteria that support biological filtration. MicroBacter Start XLM is made for these situations, including emergency recovery and aquariums with high population densities. Its live, non-pathogenic microbes help establish or replenish the bacteria involved in the nitrogen cycle.

What does MicroBacter Start XLM do in an aquarium?

It is designed to establish a new nitrogen cycle or boost an impaired one by supporting the colonization of nitrifying bacteria. These microbes help break down nitrogenous waste and reduce ammonia and nitrite levels, supporting water quality as biological filtration develops. The brand reports that a new tank usually cycles in 7 days in most cases; the timing is expressed as a typical outcome, not a guaranteed schedule.

• Supports biological filtration in new and established aquariums.
• Helps address ammonia and nitrite spikes as bacteria beds recover.
• Formulated to help prevent “New Tank Syndrome.”

When is this marine cycling aid useful?

Use it as a cycling aid for a new setup or to help rebuild nitrifying bacteria after an aquarium emergency. It is also intended for use after cleaning rocks and surfaces, following medication use, and when adding new fish. In tanks with high population densities, the formula supports the biological filtration that processes nitrogenous waste.

• Suitable for recovery when a bacteria bed has been damaged or impaired.
• Compatible with various sand and rock substrates.
• Made for marine and brackish aquarium environments.

What is in the formula, and how long does it keep?

MicroBacter Start XLM contains live, non-pathogenic microbes in a proprietary base developed to support product longevity. It is shelf-stable for over a year at room temperature, making it suitable to keep on hand for planned aquarium startups and recovery needs.

• Concentrated microbial blend formulated using extensive data compiled by microbiologists.
• Proprietary base supports longevity in the product and aquarium.
• Made in the USA by Brightwell Aquatics.

This cycling aid suits marine and brackish aquarium keepers establishing a new tank, maintaining biological filtration in a densely populated aquarium, or rebuilding bacteria after cleaning or medication. It is a 15x-concentrated microbial formula intended for aquarium cycling and bacterial-bed recovery.

Read our guide: A beginner’s aquarium set-up checklist: from bowl to tank