Dr. Tim's Aquatics One & Only Live Nitrifying Bacteria for Freshwater Aquariums

  • List Price:


  • Price:

    $29.23 FREE 1-3 dayShipping over $49

  • You Save:

    $0.72 (2%)

Autoship: &Save

$27.77(Save an extra 5%)

Simply select Autoship at checkout for easy regular deliveries.

Why Autoship?
  • FREE access to chat with licensed vets 7 days a week
  • Save 5% on all future Autoship orders.
  • No fees, no commitments - cancel Autoship anytime.
In stock
cw-icon-heart Created with Sketch. Add to Favorites

Dr. Tim's Aquatics One & Only Live Nitrifying Bacteria for Freshwater Aquariums removes toxic ammonia and nitrite, instantly working to prevent new tank syndrome by establishing a biological filter in your newly set up aquarium. Use One & Only when setting up a new tank, after a disease treatment, or during water changes. This powerful solution contains no sulfur or other offensive odors.

Key Benefits
  • Prevents and eliminates new tank syndrome by instantly working to establish a biofilter in newly set up aquariums with 100% natural living nitrifiers
  • Controls ammonia and nitrite levels instantly by removing toxic ammonia and nitrite naturally in both freshwater and saltwater aquariums
  • No sulfide or other offensive odors so you don’t have worry about overusing
  • Once added to the tank, simply add fish right away!
  • Shake well before using and keep refrigerated for longest shelf life

HAZARDS TO HUMANS: Keep out of reach of children.

Special Note

  • 2-oz bottle treats up to 30 gallons.
  • 4-oz bottle treats up to 60 gallons.
  • 8-oz bottle treats up to 120 gallons.

See all items by Dr. Tim's Aquatics

  • Item Number
  • Aquarium Type
  • Fish Type
    Tropical Freshwater, Betta, Cichlid, Goldfish
  • Product Form

100% Live Nitrifying Bacteria for aquaria


Shake well before using. Best to use the entire contents at one time. Minimum dose 10mL (2 capfuls) per 10 gal. Cannot be overdosed. Turn-off UV and remove filter socks for 48 hours. Keep refrigerated for longest shelf life. Do not freeze. Use when setting up a new aquarium, after water changes and disease treatment to quickly establish a natural biological filter.


What will One & Only do for me?

One & Only is designed for one job – to quickly establish a biofilter in your newly set-up aquarium so that your fish do not experience New Tank Syndrome (NTS), which is when the water contains such high levels of ammonia and/or nitrite that your fish die. One & Only does this by containing species of ammonia- and nitrite-oxidizing bacteria that prefer to live in the fish tank environment.

How should One & Only be added to the aquarium?

Before adding One & Only to your tank, make sure the water has been dechlorinated. Dechlorinators that contains aldehydes in its formula are harmful to One & Only. UV-sterilizers and protein skimmers should be turned off before adding One & Only and remain off for 36-48 hours after dosing.It is important to shake the bottle well before adding One & Only. If you see only a clear liquid you have not shaken One & Only well enough. Pour the One & Only over the biological filter media in your biofilter. If you do not have dedicated filter media it is fine to pour the liquid into the fish tank water.

When should One & Only be added?

One & Only should be added after the tank has been set up. At this point the water should have reached the proper temperature and have been dechlorinated. Start the filter and make sure it is functioning and then add One & Only. Fish should be added within 24 hours of adding One & Only nitrifying bacteria. An alternative to adding fish is to add some ammonia to the water.

How many fish can I add to the aquarium after dosing with One & Only?

This is the hardest question to answer because every situation is different. One & Only will dramatically reduce the time it takes to establish a biofilter in your newly set-up aquarium. However, even One & Only has limits.For instance, if you set up a saltwater tank and use uncured live rock, One & Only may not be able to initially control the ammonia concentration in the water because there will be too much decay of organic matter from the uncured live rock.Or if you let every friend of your kids feed the new fish tank such that you are grossly overfeeding the tank, One & Only will not be able to maintain low levels of ammonia and nitrite.Also, some fish species are very sensitive to any amount of ammonia in the water so these fish should be added to the tank in the first 20 or so days after set-up.In general, you can add one giant danio-sized fish per gallon when initially dosing with One & Only. Feed normally and monitor ammonia and nitrite levels in the water. You might see a little ammonia or nitrite for a day or so but this will quickly disappear. You can then add more fish to the aquarium.

Does One & Only ALWAYS have to be refrigerated?

No. One & Only should never be frozen, nor should it be kept at temperatures above 95°F. Normal room temperature will not harm the bacteria in One & Only. Perhaps it is easier to think about it this way: One & Only is not like an ice cream cone. Once ice cream is exposed to room temperatures it starts to melt, and if it completely melts you have a mess and no longer ice cream. One & Only is not like this. One & Only will last for 6 months at room temperatures (65 to 85°F). At colder temperatures (around 50°F) One & Only will last one year.

How should One & Only be treated in relation to temperature?

The best way to handle One & Only is to treat it the same way you would treat your fish. You wouldn’t keep the bag of fish you just bought at the fish store in direct sunlight in your car for hours while you continued shopping nor would you let that bag of fish freeze — the same goes for One & Only. Keep One & Only in moderate temperatures and it will be perfectly fine when you are ready to use it.

What about the longer term storage of One & Only?

At a temperature of about 50°F, One & Only will be viable for one year. Each bottle is stamped on the back with the words “best used by” and then a month and year.

When should I use One & Only?

Use One & Only when setting up a new tank and after major environmental changes to your aquarium. Examples of major changes include a disease treatment with antibiotics or chemicals that are harmful to the nitrifying bacteria, after a major gravel cleaning which can disturb the bacteria on the gravel and after a failure of the filter.

I have a Brackish water tank – which bacteria is for me?

The choice of whether to use the Freshwater One & Only or the Saltwater One & Only bacteria in a brackish water tank depends upon the salinity (or specific gravity [S.G.]) of your water.If your salinity is less than 10 ppt (1.007 S.G.) then use the freshwater formula.If your salinity is greater than 10 ppt (1.007 S.G.) then use the saltwater formula.

Rating: 2.9 of 5 stars 30 Reviews 30 Reviews 3 out of 5 Stars

60% Recommend

60% of reviewersrecommend this product

Rating: 2.9 of 5 stars 3 / 5

You've Already Reviewed This Item

30 Reviews

Showing 1-10 of 30 Reviews

  • 5 out of 5 stars

    New Tank Syndrome Solution

    By Dobermom on Aug 1, 2021

    So I dont leave many reviews for products I've bought. Let me tell you, my 60 gallon new aquarium was milky white. Every aquatic enthusiast said to wait and do nothing. So after losing a favorite Oranda, I had to try something. Dr. Tims to the rescue. In 48 hours, it completely cleared, ammonia is 0. Fish are happy and active. Ive added pic to prove it wirks!

    You liked it! Something went wrong. Please try again later. Report
  • 1 out of 5 stars

    No Effect on Tank

    By Stacy on Jul 21, 2021

    Unfortunately there was no change in water parameters after using this product. I doubled the amount needed, using the entire 120mL on a 55 gallon tank. Ammonia did not budge from prior test after a full 24 hours. Still no signs of nitrite or nitrate. It was cooler when this shipped too so I was hoping heat wouldn't impact the effectiveness.

    You liked it! Something went wrong. Please try again later. Report
  • 1 out of 5 stars

    Didn't work at all

    By FishMom on Apr 2, 2021

    All the fish ppl said this was sooo much better. I poured the whole bottle, that should treat 60 gallons, into a 10 gallon tank and nothing happened for 9 days. I put the 40 drops of ammonia(4 drops per gallon as instructed) and it brought the ammonia up to 4ppm for all 9 days, No nitrites and no nitrates. I ended up draining the tank and starting over with Fluval, which I know works in 3 days. That was last night and I already have nitrates with Fluval.

    You liked it! Something went wrong. Please try again later. Report
  • 1 out of 5 stars

    Didn’t work- disappointed

    By Heather on Mar 14, 2021

    I tried doing the fast track tank cycle following instructions to the T and the ammonia is the only thing that worked. I poured the entire bottle in my 40 gallon tank and in the filter. I can’t get the ammonia back down and it’s still showing 0 nitrites with PH of 7.6 after almost 2 weeks. I haven’t been able to even add the extra dose of ammonia in to help kick off the bacteria so I ended up doing a water change and adding other beneficial bacteria & now my tank of finally starting to cycle. I’m so bummed after all the good reviews that it didn’t work with paying all of this money for “the best bacteria” and regular bacteria that’s much cheaper is what’s working

    You liked it! Something went wrong. Please try again later. Report
  • 5 out of 5 stars

    Worked perfectly

    By Ryan on Oct 8, 2020

    My 60 Gallon aquarium wasn’t cycling fast enough so I decided to add this and the ammonia at the same time my ammonia spiked the next day then right after the nitrite spiked now nitrate is spiking so basically I had tried to cycle normally with rotting food and other thing but it still was 1 month later and nothing had really spiked so if you want to cycle a tank in like 2 weeks use this stuff.

    You liked it! Something went wrong. Please try again later. Report
  • 1 out of 5 stars

    Expired over a year

    By Goople80 on Dec 7, 2020

    Ordered from chewy. Best by date is nov 2019. It is dec 2020. Not sure if it’s effective. According to dr Tim the bacteria lives up to a year.

    You liked it! Something went wrong. Please try again later. Report
  • 5 out of 5 stars

    The best product to help cycle a new tank and keep an older cycle

    By BeBe on Aug 2, 2020

    LOVE this product! It is hard to find in the big bottles (I have a 90 gallon tank and the large bottle is what I use). I used it when setting up my new tank 2 years ago, and I use it now to help keep my cycle from crashing when I clean my canister filter. I cannot recommend this highly enough. Just make sure you shake it up really well before using. Chewy has the best price, hands down!

    You liked it! Something went wrong. Please try again later. Report
  • 1 out of 5 stars

    Best by date 7 months old

    By SoCalBunz on Oct 9, 2020

    Ordered in September 2020. Best by date is February 2020. Not very good quality control by Chewy. Usually this is a good product.

    You liked it! Something went wrong. Please try again later. Report
  • 1 out of 5 stars

    I really wanted to like this product

    By SadCustomer on Jun 10, 2020

    I am rather impatient when cycling new aquariums and after reading some reviews of this product, it seemed like the perfect solution. I put the whole bottle in the tank and used in conjunction with the Dr. Tim's ammonia solution like recommended. However. It has been 11 days since I put the bacteria in and my water is still reading 4ppm ammonia, 0 nitrites and 0 nitrates. Idk if I just got a bad bottle or what. But I am sad that this did not work.

    You liked it! Something went wrong. Please try again later. Report
  • 1 out of 5 stars

    Possibly DOA

    By Disappointed on Jul 19, 2020

    I'm thinking that this product was dead on arrival. I have used it as instructed in conjunction with ammonia, but so far it has not done what it is supposed to do.

    You liked it! Something went wrong. Please try again later. Report