Brightwell MicroBacter Start XLM — 15× concentrated bacterial culture for marine cycling

The Brightwell MicroBacter Start XLM is a 15× ultra-concentrated live suspension of non-pathogenic microbes, formulated to establish biological filtration in a new marine aquarium extremely rapidly. Made in the United States by Brightwell Aquatics, the culture quickly reduces ammonia and nitrite and prevents "new tank syndrome". Formulation based on microbiological research data.

Start XLM may show clumps, an earthy smell, and cloudy appearance in the bottle — normal quality signs indicating the culture is alive. Shake vigorously before every use. Brightwell-published shelf life: 18 months from the date of manufacture (twice the competitors').

What Start XLM is for and when to use it

Cycling a new marine aquarium — mandatory pairing with MicroBacter QuikCycl for a complete fishless cycle in ~7 days.
Restart after an incident — recovery after a major sump clean, rock replacement, or disinfection.
Ammonia spike correction — emergency treatment on an NH₃/NO₂ spike in an established tank.
Reinforcement after treatment — after a medication cure that weakened the filter bed.

Brightwell official use

Cycling a new tank: 30 mL per 25 US gal for initial seeding.
Additional dose: 10 mL per 25 US gal if ammonia or nitrite exceeds 0.2 ppm.
Minimum required: 1.2 mL per US gal of total aquarium volume.
Cleaning / recovery cure: 10 to 30 mL per 25 US gal depending on issue severity.
Emergency ammonia spike: 30 mL+ per 25 US gal, then 5 mL every 30 minutes until NH₃ drops.
Shake well before use. Do not freeze.

Equipment restrictions during cycling (Brightwell official)

Turn OFF for the full duration of cycling:

UV sterilization
Ozonation
Protein skimmer
Activated carbon filtration (do not resume until cycle end or 30 days elapsed)

Counter-productive during cycling:

Live sand or pre-seeded artificial rock
Competing bacterial products (MicroBacter7 or Clean before cycle end)
Probiotic salts containing dry bacteria
Phosphate removers or GFO before 30 days, or until PO₄ exceeds 0.04 ppm
Iodine compounds (Lugol's) or nitrate removers before 30 days post-cycle

Specifications

Brand: Brightwell Aquatics (made in the USA)
Available sizes: 125 mL, 250 mL, 500 mL, 1 L, 2 L, 4 L, 20 L
Concentration: 15× live concentrated suspension
Type: bacterial culture for marine cycling only (Start XLF for freshwater)
Storage: keep below 27 °C (80 °F); refrigeration at 10 °C (50 °F) extends potency; do not freeze
Shelf life: 18 months from date of manufacture

Why choose Brightwell at ReefSolution

Brightwell MicroBacter QuikCycl — the mandatory ammonia source paired with Start XLM for a complete fishless cycle.
Brightwell MicroBacter7 — the maintenance bioculture to use from one week after the QuikCycl + Start XLM cycle ends.
Brightwell MicroBacter Clean — the anti-detritus complement to start one week post-cycle to reduce "ugly stage" issues.

Frequently asked questions

How long does a marine cycle with Start XLM and QuikCycl take?

Brightwell states about 7 days under optimal conditions. Cycle complete when ammonia and nitrite drop to zero and nitrate reads 0.25 ppm or higher. Verify with accurate titration tests before adding any livestock.

Can Start XLM be used without QuikCycl?

For a full cycle, Brightwell explicitly recommends the Start XLM + QuikCycl duo. Start XLM alone can help on an established tank (reinforcement after treatment, spike correction), but a proper new-tank cycle needs QuikCycl's ammonia source to feed the bacteria.

Does MicroBacter Start XLM need refrigeration?

Brightwell states: store below 27 °C (80 °F), and refrigeration at 10 °C (50 °F) extends potency. Never freeze. Published shelf life: 18 months from the manufacture date printed on the bottle.

Can I run activated carbon while cycling with Start XLM?

No — Brightwell is explicit: activated carbon must not be used before the cycle fully ends or 30 days have elapsed since start. Same constraint for UV, ozone, skimmer: all off until cycling is confirmed complete by testing.