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Brightwell Aquatics MicroBacterStart XLF - 15X Concentrated Live Tank Starter for Cycling New Freshwater Aquarium and Establishing Nitrifying Bacteria

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Arrives Friday, Jul 10
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Size: 20-L


Features

  • 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. Supplied in a proprietary base which provides for maximum longevity.
  • 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.
  • Takes 5-7 days to cycle.

Description

MicroBacterStart XLF 15X creates a nitrifying biological filter in freshwater aquaria of all types and is particularly useful for new startups, resulting in tank cycling in 5 to 7 days in most cases. It quickly removes toxic ammonia and nitrite naturally through nitrifying bacterial action. Even though this product is potent, it may be overdosed at up to 5 times rated dosage during aquarium upsets. It should be your first choice to remove ammonia during emergencies where the filter has been inadvertently killed. MicroBacterStart XLF 15 X is a highly concentrated, selective complex of live, extremely effective microbes and enzymes that rapidly reduces the concentrations of organic nitrogen, ammonia, and nitrite in freshwater ecosystems, leading to greatly improved water quality and much faster cycling. Use of MicroBacterStart 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 for clumps to form in the product and for the product and the aquarium to have an “earthy” smell or smell “off” and for the aquarium water to become cloudy and the smell and cloudiness to 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 other bacteria species that will be compatible with this nitrifying bacteria product until the cycle is complete. To add other bacteria will significantly lengthen the time it takes to cycle. Storage: Although product can withstand elevated temperatures for short periods of time, for best longevity and highest potency, keep below 80 deg F and if possible, refrigerate at 50 degrees F. Do not freeze! Freezing can kill the bacteria.

Brand: Brightwell Aquatics


Liquid Volume: 20 Liters


Item Weight: 22.88 Kilograms


Unit Count: 1 Count


Manufacturer: Brightwell Aquatics


Package Dimensions ‏ : ‎ 16.2 x 13 x 12.6 inches; 50.45 Pounds


Item model number ‏ : ‎ BACSTARTXLF20L


Date First Available ‏ : ‎ April 10, 2020


Manufacturer ‏ : ‎ Brightwell Aquatics


Best Sellers Rank: #11,760 in Pet Supplies (See Top 100 in Pet Supplies) #94 in Aquarium Water Treatments


#94 in Aquarium Water Treatments:


Customer Reviews: 4.6 4.6 out of 5 stars (1,368)


Brand Name: Brightwell Aquatics


Manufacturer: Brightwell Aquatics


UPC: 096647000565


Model Number: BACSTARTXLF20L


Manufacturer Part Number: BACSTARTXLF20L


Unit Count: 1 Count


Item Type Name: Water Conditioner


Included Components: MicroBacterStart XLF


Liquid Volume: 20 Liters


Item Weight: 22.88 Kilograms


Allergen Information: Sulphites Free


Frequently asked questions

If you place your order now, the estimated arrival date for this product is: Friday, Jul 10

Yes, absolutely! You may return this product for a full refund within 30 days of receiving it.

To initiate a return, please visit our Returns Center.

View our full returns policy here.

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Top Amazon Reviews


  • Great bacteria booster for starting and supporting a cycle
Size: 125-ml
I’ve had very good results using Brightwell Aquatics MicroBacter alongside cycled or seeded bio media. Using both together really helps fast track the cycling process instead of starting from zero. It’s easy to dose and has been especially helpful when setting up new tanks or reinforcing an existing cycle after changes. Pairing it with established media has made cycling much quicker and less stressful. I like keeping it on hand for both new setups and ongoing tank maintenance. ... show more
Reviewed in the United States on February 17, 2026 by Bee Bee

  • 100 % recommend!!
Size: 125-ml
Amazing product!! My tank was cycling for over a month and no changes, my ammonia 0ppm, nitrite super high and barely any nitrate, and I was using brightwell florin bacter 7 which is great as well but for some reason wasn’t working for this bigger tank. So I did some research and it said I could just substitute the florin Bacter for the micro bacter start XLF since they’re the same brand and are compatible (do your research) so I did and after 4 days dosing it my tank was ready and no nitrites at all!! It was like magic. I recommend this to start cycling the tank since it’s so strong and then continue after water changes with the Florin Bacter7 which is what I’m doing and it’s going great so far. Also keep both in the fridge. One think I must add is that for some reason I thought the bottle was going to be bigger because of the picture they display but it’s still enough because it’s concentrated and it’s only to use once in a while. I also use it when I have ammonia in my nano tank I dose it for 2-3 days and it boosts the nitrifying bacteria 🙌🏻 love it and will buy again and again. ... show more
Reviewed in the United States on December 5, 2025 by Grumpy Gills 🐠🦐❤️ Grumpy Gills 🐠🦐❤️

  • Good stuff worth the money
Size: 125-ml
Absolute best way to start your tropical fish tank and have a perfect environment for fish survival. This stuff is a must and it works well.
Reviewed in the United States on September 25, 2025 by Keith Simon

  • Great stuff
Size: 500-ml
This is the best quick start for bacteria that i have used. I’ve tried all the other brand names that everyone is aware of. My tank was cycled in a week. Will be my go to from now on.
Reviewed in the United States on January 21, 2026 by Chinagirl

  • errr probably worked?
Size: 125-ml
So I moved from a 29 gallon to a 75 gallon and I only brought one decoration and a sponge filter from the 29 gallon. I noticed after 2 days my ammonia was converting but I honestly can't tell if its because my bacteria survived or because this is a great product. Nonetheless, I'm sure it aided in the process. I kind of bought this cause DrTim's was out but I'm sure it actually does work. Also the cap had a little hole so every time I shook a little would come out. Didn't affect my water clarity or anything. For the price I think it's alright. ... show more
Reviewed in the United States on November 17, 2025 by Emmanuel

  • This stuff works
Size: 500-ml
I was having a bit of a problem 'cycling' the 125-gallon tank with Seachem Stability. Ordered the Brightwell Aquatics MicroBacterStart XLF and, combined with Fluval's Biological Enhancer added on top of the Seachem Stability, the tank was completely cycled within 48 hours. Granted, the Seachem had the ammonia taken care of, but the nitrites were just not budging and would escalate rapidly without major water changes and additions of Seachem Prime daily. I am SOOO glad to have found the Brightwell product. ... show more
Reviewed in the United States on February 28, 2024 by Cyndie Stevens

  • Love it!!
Size: 125-ml
This worked great! Wonderful purchase for cycling my axolotl tank, and worked like a charm. Would recommend 👌🏼
Reviewed in the United States on September 28, 2025 by Daniella Cunningham

  • Multi-purpose
Size: 250-ml
I got it to do two things: Keep the water clear in my pond, and help make liquid fertilizer. If you didn't know, you can put grass clippings and other organic stuff into water, and the water will leach out a lot of the good stuff. Eventually this progresses into a fermentation, and finally, nitrization. That's when bacteria start really turning the nitrogen in the liquid into something plants can use. Well, my liquid fertilizer mixture is still sitting, but not long after I added some of this, the water turned black. This is a good sign and shows that everything's working, and quickly! As for my pond, it looks great and has no problems. I recommend this item to people getting into homesteading, aquaculture, regenerative agriculture, making their own fertilizer, etc. ... show more
Reviewed in the United States on June 27, 2024 by Z

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