Brightwell Aquatics

MicroBacter Start XLF - Live Nitrifying Bacteria

Grouped product items
MicroBacter Start XLF (250 mL)

SKU: 252498

In stock

$10.24 $12.05

- +
MicroBacter Start XLF (500 mL)

SKU: 252499

In stock

$18.56 $21.84

- +

Professional 15X strength live nitrifying bacteria for cycling new freshwater aquariums

  • Results in cycling in about 5 to 7 days in most cases
  • Useful for rapidly re-establishing nitrification bacteria in case of an emergency
  • Particularly useful in aquaria with high bioloads and when adding new fish
  • Helpful to re-establish nitrifying bacteria after cleaning rocks or after use of medications.
  • Rapidly reduces of ammonia and nitrite
  •  Prevents “New Tank Syndrome”


MicroBacter Start XLF is a professional 15x strength live tank starter nitrifying bioculture for rapidly cycling new freshwater aquariums, and for recovering from overcrowding or disasters where the bacteria bed has been damaged or when adding new fish. It quickly removes toxic ammonia and nitrite naturally through non-pathogenic nitrifying bacterial action.  Even though this product is extremely potent, it may be overdosed at up to 5 times the rated dosage during aquarium upsets.  It should be your first choice to remove ammonia during emergencies where the filter has been inadvertently killed or under overcrowding.


Technical Background

MicrōBacter Start XLF is a highly concentrated, selective complex of live, extremely effective microbes and enzymes that rapidly reduces the concentrations of organic nitrogen - i.e. ammonia, and nitrite in freshwater ecosystems, leading to greatly improved water quality and much faster cycling. Use of MicrōBacter Start XLF does not alleviate the requirement for regular partial water changes to help maintain proper concentrations of elements that are vital to long-term health and survival of aquarium inhabitants.

Notes - It is normal that clumps may form in the product and the product and the aquarium may have an “earthy” smell or smell “off” and the aquarium water could become cloudy and the smell and cloudiness could remain for many hours after using. This is due to the bacteria themselves and is an indication of quality and is the reason it is necessary to shake product well immediately before using. Brightwell recommends that you not use any other type of bacteria product until your cycle with this product is complete. There are no dry bacteria species that will be compatible with this nitrifying bacteria product or that are useful to cycle an aquarium! 

Storage - Although product can withstand elevated temperatures for short periods of time (a few days), for best longevity and highest potency, keep below 80°F and if possible, it will be best kept refrigerated at 50°F. Do not freeze! Freezing can kill the bacteria. (This product will usually withstand a freeze or two in transit in the winter, but do not freeze, thaw, freeze thaw.) If the product arrives frozen, then thaw at room temperature, NEVER MICROWAVE!


A word about substrates: Most aquarium bacteria and certainly those in MicrōBacter Start XLF live on substrates, that is, they attach themselves to surfaces of rocks, piping and any other surfaces that are available. Most modern aquariums do not have enough surface area. Brightwell recommends that you provide plenty of bacterial surface area by providing addional filtration media, such as Xport biomedia which has the highest surface area per unit volume of any medium in the world, or the less expensive MicroBacter Lattice Medium.


Instructions & Guidelines

Important: First, use Brightwell Erāse-Cl to completely remove chloramines and chlorine from tap water. Chloramine and chlorine are lethal to the bacteria in this product and if not removed, will cause it to fail! Shake product vigorously immediately before using it. Add the appropriate volume of MicrōBacter Start XLF (see below) to the aquarium in an area of high flow to promote dispersion. Do not use any other bacteria product until cycling with this product is complete!


To seed Biological Filtration in new aquaria

Add 30 ml (6 capfuls) of MicrōBacter Start XLF per 25 US-gallons (95 L) of aquarium water. Add one or more hardy fish. Remove filter socks, turn UV-sterilization off for the complete period of cycling until you are finished dosing this product. Test ammonia and nitrite levels daily or as needed, if either is above .2 ppm, then you can dose MicrōBacter Start XLF again at a lower dose of 10 ml per 25 US-gallons if desired. At 7 days or longer, Tank is cycled if, and only if, both ammonia and nitrite levels are zero and nitrate is well above zero. If either ammonia or nitrite levels are above zero, then the tank is not yet fully cycled and you should not add fish. if the nitrate is not above zero (at least .25 ppm), then tank is not yet fully cycled and you should not add fish.


To replace bacteria killed by extensive cleaning of substrates and surfaces

Add 10 to 30 ml per 25 US-gallons (95 L) depending on perceived damage to filter bed, and ammonia level.


To replace bacteria killed by medications, overcrowding or emergencies

Add 30 ml per 25 US-gallons (95 L) depending on perceived damage to filter bed. Then add 5 ml per half hour until ammonia levels come down.


Ongoing care after the aquarium is cycled

To provide ongoing biological stability to a cycled aquarium: Switch to FlorinBacter Clean or FlorinBacter 7 after tank is fully cycled and one week has elapsed. This will greatly reduce problems while the aquarium is maturing. At that point you can add Florin Axis to provide a carbon source for the FlorinBacter, and plants if desired.

Write Your Own Review
You're reviewing:MicroBacter Start XLF - Live Nitrifying Bacteria
Your Rating
Only registered users can write reviews. Please or

Product Questions

No questions yet. Be the first to ask the question!