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"Brightwell Aquatics MicroBacterStart XLM" 15x Strength Live Tank Starter Nitrifying BioCulture for Newly Cycling Marine Reef Tanks
"Brightwell Aquatics MicroBacterStart XLM" 15x Strength Live Tank Starter Nitrifying BioCulture for Newly Cycling Marine Reef Tanks
"Brightwell Aquatics MicroBacterStart XLM" 15x Strength Live Tank Starter Nitrifying BioCulture for Newly Cycling Marine Reef Tanks
"Brightwell Aquatics MicroBacterStart XLM" 15x Strength Live Tank Starter Nitrifying BioCulture for Newly Cycling Marine Reef Tanks
"Brightwell Aquatics MicroBacterStart XLM" 15x Strength Live Tank Starter Nitrifying BioCulture for Newly Cycling Marine Reef Tanks
"Brightwell Aquatics MicroBacterStart XLM" 15x Strength Live Tank Starter Nitrifying BioCulture for Newly Cycling Marine Reef Tanks

"Brightwell Aquatics MicroBacterStart XLM" 15x Strength Live Tank Starter Nitrifying BioCulture for Newly Cycling Marine Reef Tanks

Brand: Brightwell Aquatics

Regular price $12.99 On Sale

Only 4 left in stock!

Estimated Arrival: Between Jan 29 and Feb 04. *ETA for USA only. For accurate lead times, call us at 727-214-7750

Large, Custom, Or Backorder: Arrival Times May Vary.

Shipping Policy: Little or No Shipping Charges for Regular-Sized Items; We Cover Part of the Freight Costs for Large Items Shipped Nationally. See Shipping Policy.


MicrōBacter Start XLM 15X creates a nitrifying biological filter in marine & brackish aquaria of all types and is particularly useful for new startups, resulting in cycling in about 7 days  in most cases, if directions are followed, and no competeing bacteria or nothing toxic is added (please read this whole webpage.)  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 emergencies.  It should be your first choice to remove ammonia during emergencies where the filter has been inadvertently killed or when experiencing overcrowding.


Technical Background

MicrōBacter Start XLM 15X 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 marine and brackish ecosystems, leading to greatly improved water quality and much faster cycling. Use of MicrōBacter Start XLM 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.

Before you get started, you will need:

  1. An appropriately sized bottle of MicrōBacter Start XLM.  At a minimum, you will need 1.2 ml of product for every gallon of aquarium capacity.  For example, if you have a 100 gallon tank, you will need a minimum of 120 ml of MicrōBacter Start XLM.
  2. a good grade of the following test kits:  ammonia, nitrite, nitrate, pH
  3. a bottle of Brightwell Erāse-Cl to remove all chlorine or chloramines (if you skip this, you can kill the bacteria in MicrōBacter Start XLM.)
  4. Of course, you will need an excellent aquarium salt mix, such as Brightwell NēoMarine and purified tap water.  Brightwell recommends the tap water be filtered by Reverse Osmosis with post deionization and that you change your carbon filter regularly.



There are several reasons why hobbyists do not achieve a fast 7 day (approximately) cycle with this product.  These are all controllable if careful attention is paid.  Even when these factors are present, the tank will still cycle, it will just take more time.  1) The overuse of ammonia or using household ammonia!  Ammonia is toxic to bacteria, even though they consume it, just like it is to fish and invertebrates, so if you overdose the ammonia, it will kill some of the bacteria and it will take longer to cycle!  You will still achieve an excellent and strong cycle, it will just take longer, possibly much longer.  Also, if you purchase household ammonia, it may have toxic additives, dyes, surfactants and cleaning agents that will stunt the multiplication of the bacteria in the product.  Brightwell recommends that you use MicroBacter QuikCyclTM as directed and test so that you don't overdose! 2) In a brand new aquarium, there can sometimes be surfactants, mold release compounds or oily chemicals that coat brand new glass, acrylic, tubing and pumps.  These compounds can negatively affect the cycle.  It is therefore recommended that you clean all new parts with a mild soap and water and then RINSE THEM VERY WELL!  (Do not use antibacterial soap!) This should remove the compounds that can stunt the multiplication of the new bacteria  3) Brightwell recommends that you not use any other type of bacteria product until your cycle with this product is complete !!! Do not even use MicrōBacter7 or MicrōBacterCLEAN until the cycle is complete (then you will want to use one of them to help through the "ugly stage".  (MicrōBacterCLEAN will work best for this.)  Do not use live sand and particularly DO NOT USE dry seeded artificial live rock until cycling 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 at all! To use a dry bacteria will only lengthen the time it takes to cycle by many weeks and increase your work many times!  Wet cycled live rock or even previously cycled wet man made rock will work fine (although this may be a bad idea due to the possibility of introducing parasites or pathogens from another aquarium).  Dry sand is fine to use, but not bagged, so called "live sand"  because the manufacturer will usually introduce other bacteria species to replace the natural bacteria that will die during storage and these will be counterproductive to your cycle.  Also, several so called "probiotic" salts are available.  Again, there are no species of bacteria that are conducive to cycling that are available in a dry form.  Therefore, do not use any salt that is labelled as probiotic or says it contains dry bacteria.  DO NOT USE CARBON IN YOUR FILTER until the aquarium has cycled fully and 30 more days has passed.  DO NOT USE PHOSPHATE REMOVERS, FILTER RESINS, GFO or other non-biological filtration media until the aquarium is over 30 days old and then you register phosphates on your test kit over .04 PPM.  If you do, you will lengthen the cycle.  Bacteria require some phosphate to multiply rapidly!  Use XportTM, MicroBacter LatticeTM or other filtration media that needs to be populated with bacteria!  These will work well.  4)  The addition or dosing too soon of iodine compounds, nitrate removers (such as Red Sea NOPOX), or other additives that are bactericidal.  It is a good idea to wait 30 days to add these.

Storage & Shelf Life

Shelf life is typically 18 months from manufacture date (more than twice as long as any other nitrifying bacteria and 8 or more times as long as most others).  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 to much prolong shelf life. 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 and keep from freezing if at all possible.)  If the product arrives frozen, then thaw at room temperature, NEVER MICROWAVE!


A Word About Substrates 

FOR EXPECTED AND ADVERTISED CYCLE RESULTS, PLEASE ONLY USE MICROBACTER START XLM WITH DRY ROCK AND DRY SAND. Most aquarium bacteria and certainly those in MicrōBacter Start XLM live on substrates, that is, they attach themselves to surfaces of rocks, piping and any other surfaces that are available. Live Rock and Live Sand has bacteria already present on them that will compete for the same space to colonize as the bacteria culture in MicroBacter Start XLM, and the live rock / sand bacteria most likely is not optimized to remove ammonia, nitrites, and nitrates like the culture in MicroBacter Start. Using live rock and live sand will lengthen your cycle by 3-5x, which defeats the point of having live rock / sand to start with. So use Dry Rock and Dry Sand wherever possible.

Most modern aquariums do not have enough surface area for bacteria to colonize effectively. The advent of artificial "live rock" has made available products made from concrete or plastic that look like live rock, but do not have the porosity, so their surface area is too small to support the number of bacteria needed to properly filter the aquarium. Brightwell recommends that you provide plenty of bacterial surface area, either through plenty of porous natural aragonite live rock, or by providing additional filtration media, such as CerMedia Marine Pure (Two Tides recommends the Marine Pure 2" Cubes as they provide the best balance of bacteria cultures and are also the most structurally sound and utilize space efficiently)

Function: Cycle new reef aquariums quickly with little to no "ugly phase" of mass algae growth by rapidly establishing a healthy bed of nitrifying bacteria to naturally reduce ammonia and nitrite.

Dosing Recommendation: 30mL (6 capfuls) / 25 Gallons

Size Recommendations for Full Aquarium Systems (with Filtration):

  • 125mL = up to 100 Gallon Full System (~75G Tank)
  • 250mL = up to 200 Gallon Full System (~160G Tank)
  • 500mL = up to 400 Gallon Full System (~320G Tank)
  • 2L = up to 1500 Gallon Full System (~1200G Tank)

Usage Notes:

Have any further questions that aren't answered here? We'd love to hear from you, and learn how we can help you be as successful as possible in this wonderful hobby.

You can call in to 727-214-7750 to speak with Tyler from our team to determine how to create your Ideal Aquarium Build.

Also feel free to reach out to us at and we will aim to respond back within the next few hours.


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