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Brightwell Aquatics MicroBacter Start XLM

Brightwell MicroBacter Start XLM New Tank Bacteria


Brightwell Aquatics MicroBacter Start XLM is a professional 15x strength powerful live tank starter nitrifying bacteria for rapidly cycling new marine fish and reef aquarium, and for recovering from overcrowding or disasters where the bacteria bed has been damaged or when adding new fish.  It is also quite useful after rearranging decorations or performing major maintenance, such as cleaning substrates or biological media to "recharge" the nitrifying bacteria population.



Brightwell Aquatics MicroBacter Start XLM  250ml / 500ml


  • Super concentrated 15X Suspension of LIVE non-pathogenic microbes, specifically formulated to extremely rapidly establish biological filtration in new aquarium set-ups, and to enhance the rate of nitrification in existing systems.
  • Useful for rapidly re-establishing nitrification bacteria in case of an emergency
  • Particularly useful in aquaria with high population densities and when adding new fish
  • Helpful to re-establish nitrifying bacteria after cleaning rocks and surfaces and after use of medications.
    1. Rapid reduction of ammonia, and nitrite.
    2. Prevents “New Tank Syndrome.”
  • Supplied in a proprietary base which provides for maximum longevity
  • Formulated utilizing extensive data compiled by microbiologists.

MicroBacter Start XLM 15X creates a nitrifying biological filter in the marine aquarium 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 competing 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.


  • Important: First, ensure that your water is chloramines and chlorine free when used tap water, as they are lethal to the bacteria in this product and if not removed, will cause it to fail!
  • Shake product vigorously immediately before using.  
  • Add the appropriate volume of MicrōBacter Start XLM (see below) to the aquarium in an area of high flow to promote dispersion.
  • Do not use “live sand” or “dry seeded artificial live rock” until cycling with this product is complete for several weeks! (In fact, Brightwell recommends that you do not use dry seeded artificial "live rock" ever.  The best choices are aquacultured live rock, rock from the ocean, naturally cycled artificial rock sold wet, unseeded dry artificial rock, dry florida aragonite, other natural aragonite, marco rock and the like.  Any rock that already contains a bacteria and is dry, will damage the cycling process and in our experience takes too long to cycle and cycles the wrong nutrients - dry seeded rock will not properly cycle ammonia because it is the wrong species of bacteria)
  • To seed Biological Filtration in new aquaria: Add 30 ml (6 capfuls) of MicrōBacter Start XLM per 95 L of aquarium water.
  • Add one or more hardy fish.
  • Remove filter socks, turn UV-sterilization and/or ozonation and/or protein skimmer 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 are above .2 ppm, then you can dose MicrōBacter Start XLM again at a lower dose of 10 ml per 95 L, 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 95 L depending on perceived damage to filter bed, and ammonia level.

To replace bacteria killed by medications, overcrowding or emergencies: First, dose the aquarium with Brightwell Erase Cl to detoxify the ammonia until the bacteria can consume it!  Dose daily with Erase Cl, if necessary to keep ammonia under control until the bacteria are fully in control.  Add 30 ml per 95 L or more of MicroBacter Start XLM, depending on perceived damage to filter bed. Then add 5 ml per half hour until ammonia levels come down.

To perform a Fishless Cycle: Purchase a bottle of MicroBacter QuikCyclTM to use simultaneously with this product, MicrōBacter Start XLM according to the QuikCyclTM label. Fishless cycling requires both products to be used together. This product will provide the bacteria and the QuikCycl will provide the nutrients.  GO SLOW WITH QuikCyclTM!  All of the ammonia you put in will become nitrate that you will have to remove later.

Ongoing care after the aquarium is cycled: To provide ongoing biological stability to a cycled aquarium: Switch to MicrōBacterCLEAN after tank is fully cycled and one week has elapsed. This will greatly reduce problems during the "ugly stage."  At that point, you can add Reef BioFuelTM to provide a carbon source for the MicroBacterClean, if desired.  If you want to switch to MicrōBacter7 the best time will be when the aquarium has been running for 4 to 6 months.

Technical Background
MicroBacter 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.



We want you to be fully happy with your new macroalgae addition. Therefore we offer you a hassle free Satisfaction Guarantee.  

If you are not 100%  happy with the macroalgae you have received on arrival we will refund you the full money back.    *1
We even will cover the return costs. The refund will be offered after we arrived and checked the returned marine algae.

*1 = Valid for UK Orders only, please see our Terms for EU orders HERE 


We offer for sale macroalgae from our mature macroalgae mother colonies in a premium quality & 100% healthy within the UK and EU.
All live algae species are sustainably grown in the UK.

All macroalgae will be well protected when posted to you to ensure that it will arrive in the best condition at yours.


We won't be beaten on the premium quality of our live algae cultures, and surely not on the price either!

Have you seen the same macroalgae somewhere else cheaper?

Please just send us a message HERE and we will check your request within 24 hours ( working days only ).

When we can match the other price we will send you a discounted offer which will be valid for the next 7 days after receiving our email.
This offer will be just valid for purchases using the same email address provided before.

The price match offer is only valid for identical, same size/amount and available macroalgae species.
As a proud UK based tax paying business, we don't price match any offers against auction sites or from private sellers.

The price match offer is just valid for UK deliveries. We reserve the right to refuse a price match request.

If you have any questions please don't hesitate to contact us.

Your Livealgae UK

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