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Is It Possible to Add Too Much Bacteria to a Fish Tank?

Can You Add Too Much Bacteria to Fish Aquariums San Diego, CA

When you review aquarium maintenance guides, you’ll notice most of them recommend bottled bacteria as one of the most essential fish tank supplies and adding small doses of the bacteria each time a water change is performed. Other guides don’t include this recommendation at all. Instead, they suggest adding a few drops of enhanced water conditioner, which is incorrect. Some fish keepers will tell you there’s no need to add more bacteria to a freshwater or reef tank as long as you’re doing everything to keep ammonia levels as close to zero as possible, and this is also fake news.

Not-so-new research confirms the necessity of healthy bacteria and the benefits of adding it to the system every now and then to re-establish the healthy strains. At the same time, adding too much bacteria isn’t really an issue because a balanced ecosystem will enact some level of bacterial regulation.

Bacterial Bloom as a Sign of Too Much Nitrobacter

When you establish a tank prior to introducing the first few hearty fish or invertebrates, you’ll notice a period of cloudy water that might last two or three days. This is known as bacterial bloom, and it’s not only expected but also desired. Whether you established the tank naturally with plants and liquid bacteria or by means of bottled bacteria only, the Nitrobacter colonies will need a period of adjustment during which the species will feed and generate waste. After this period, the colonies will settle on their favorite spots, which are invariably the biological filter media, and this is why the cloudiness goes away.

Subsequent Bacterial Bloom

As you continue stocking the tank with more species, you may notice additional periods of cloudiness, which will once again clear up even faster than the first time. You might observe a similar situation when adding a few drops of bottled bacteria when changing the water, and this denotes a temporary overpopulation of Nitrobacter microorganisms, but the water will clear up even faster than when you completed the nitrogen cycle the first time around.

Excessive Aquarium Bioload Issues

The bioload of a tank is the sum of all fish waste. This includes uneaten food, secretions, and excrement. As fish waste breaks down and dissolves, Nitrobacter consumes the harmful nitrites and nitrates, thus preventing ammonia levels from rising. In a pond or tank that’s overstocked, the bacterial colonies won’t be able to handle the higher bioload, and this cannot be corrected by adding more bottled bacteria.

Bacteria and Water Oxygenation Levels

Similar to just about all living organisms, Nitrobacter will consume oxygen to survive. While it’s common to think larger bacterial colonies will take up more oxygen from the water, this isn’t a situation to be concerned with because the ecosystem will self-regulate. To be on the safe side of biochemical oxygenation, all tanks can benefit from having a few aquatic plants and air bubbles. Even planted aquariums with CO2 can benefit from air bubbles being pumped into the aquarium at night when the CO2 is off.

If you need beneficial bacteria for your aquarium, you can find what you need at Aquatic Warehouse. We also carry a wide array of other crucial supplies, whether you need a dosing pump, LED lighting, filtration, or testing kits. Stop by our store in Kearny Mesa, order your supplies from our website, or give one of our knowledgeable representatives a call today at 858-467-9297.


Contact Information

  • Address: 5466 Complex Street Suite 204
    San Diego, CA 92123
  • Phone: (858) 467-9297
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