What eats bacteria in aquarium?

Keeping an aquarium clean and healthy requires maintaining a balance between different organisms and nutrients. One important aspect is controlling bacteria levels, as too much bacteria can cause cloudy water, slime build-up, and unhealthy conditions for fish. Fortunately, there are several natural methods to help control bacteria in an aquarium environment.


Many fish species common in home aquariums will consume bacteria as part of their diets. This includes bottom-feeders that sift through substrate looking for food particles, algae-eaters that scrape tank surfaces, and filter-feeders that consume microorganisms from the water column.

Some examples of fish that eat aquarium bacteria include:

  • Catfish
  • Loaches
  • Plecos
  • Corydoras
  • Guppies
  • Mollies
  • Tetras
  • Rainbowfish

These fish graze on bacteria along with other food sources. Their feeding helps clean tank surfaces and reduce overall bacteria levels. Targeted bacteria-eating fish can be used to help control specific bacterial outbreaks in an aquarium as part of an overall tank maintenance strategy.


Many invertebrates common in home aquariums also consume bacteria:

  • Snails
  • Shrimp
  • Crabs
  • Crayfish
  • Clams
  • Starfish

Snails such as nerites and mystery snails scrape algae, diatoms, and biofilm off surfaces as they move around the tank. Shrimp pick at substrate and decor to filter out edible matter. Crabs, crayfish, clams, and starfish help clean substrate, consuming decaying matter and microorganisms.

Certain invertebrates can be used strategically to target specific bacterial blooms. For example, introducing nerite snails can help gain control of stubborn green algae growth fed by high bacteria levels. Using shrimp or crabs may help reduce debris and slime buildup in substrate and decorations.

Live Plants

Live aquarium plants provide natural filtration in a tank by consuming dissolved organic compounds, competing with algae for nutrients, and absorbing nitrogen compounds produced by fish, invertebrates, and bacteria. By helping control overall nutrient levels and algae growth, aquatic plants indirectly limit resources available for bacteria proliferation.

Some plant types are especially efficient nutrient absorbers and competitors against algae. Examples include:

  • Java fern
  • Java moss
  • Anubias
  • Cryptocorynes
  • Floating plants like duckweed or water lettuce
  • Fast growing stem plants like hornwort, anacharis, and cabomba

A heavily planted tank will go a long way towards limiting bacterial growth and maintaining water quality. The plant root systems also provide surface area for beneficial bacteria involved in the nitrogen cycle to colonize.

Algae Eaters

Algae-eating fish, invertebrates, and organisms help control bacteria by competing with algae for resources like nutrients, CO2, and light. Algae and bacteria often coexist in aquarium environments, feeding off similar resources and the waste products of each other. Controlling algae growth indirectly limits bacteria levels as well.

Some examples of algae eaters include:

  • Plecos
  • Otocinclus catfish
  • Amano shrimp
  • Nerite snails
  • Ramshorn snails
  • Siamese algae eaters
  • Florida flagfish

Strategic use of algae eaters can be an effective part of an overall bacteria control strategy by limiting algae growth.

Clean Up Crews

Tank clean up crews using organisms like bacteria-eating fish, invertebrates, and algae eaters all together can form an efficient bacteria control strategy. As they forage and graze in the tank, each element of the clean up crew helps target different areas and food sources.

Examples of clean up crews might include:

  • Catfish and loaches working the bottom substrate
  • Snails and shrimp clearing decorations and tank walls
  • Algae eating fish and invertebrates controlling algae growth
  • Fast growing floating and stem plants soaking up nutrients

When the different organisms work together, they can form a natural bacteria control system through competition, grazing, and overall tank cleaning.

Ultraviolet Sterilizers

Ultraviolet or UV sterilizers use UV radiation to kill free floating bacteria, viruses, and parasites as water flows through the device. They are often installed inline with filter systems.

UV exposure damages the DNA of microorganisms rendering them unable to reproduce. UV sterilizers essentially deactivate bacteria flowing through them without chemicals. They provide bacteria control for the overall water column but do not address bacteria established in substrate or on tank surfaces.

Protein Skimmers

Protein skimmers work by creating air bubbles that organic compounds like bacteria stick to. These bubbles are then skimmed out of the water column and removed from the tank.

In saltwater tanks, protein skimmers are an efficient way to reduce dissolved organic carbon compounds that bacteria feed on before they can trigger bacterial blooms. They help control bacteria levels by limiting their food sources.

Maintaining Stable Tank Conditions

Bacteria tend thrive under unstable conditions like fluctuating water parameters, excess nutrients, or sudden changes. Maintaining stable, healthy tank conditions goes a long way towards limiting bacteria growth.

Ways to promote stable tank conditions include:

  • Regular partial water changes
  • Testing and adjusting water parameters
  • Avoiding overstocking
  • Not over feeding
  • Filter maintenance
  • Gravel vacuuming
  • Balancing light duration

Vigilant tank maintenance keeps nutrient levels under control and allows tank inhabitants to outcompete nuisance bacteria.


Certain aquarium-safe antibiotic, antifungal, and anti-parasitic medications can be used to treat stubborn bacterial infections. These should be used cautiously and only when necessary.

Some common antibacterial medications include:

  • Tetracycline
  • Minocycline
  • Erythromycin
  • Trimethoprim-sulfamethoxazole
  • Methylene blue
  • Nitrofurazone

Always follow medication labels carefully and remove carbon filtration when using antibiotics. Targeted medication can help eliminate acute bacterial outbreaks when other methods fail.

Beneficial Bacteria

While some bacteria can cause problematic overgrowth, there are also many beneficial bacteria that help keep aquarium ecosystems balanced. These beneficial bacteria play key roles in the nitrogen cycle, aiding the biological filtration that controls dangerous nitrogen compounds like ammonia and nitrite.

Some examples of beneficial bacteria in aquariums include:

  • Nitrosomonas
  • Nitrobacter
  • Nitrospira
  • Pseudomonas

These bacteria use nitrogen compounds as an energy source, converting toxic ammonia into nitrite, and then nitrite into less harmful nitrate. Their presence indicates an active, healthy nitrogen cycle. Methods to promote populations of these beneficial bacteria include:

  • Using established filter media
  • Adding supplements on new tank setup
  • Allowing time for bacterial colonies to establish on surfaces
  • Avoiding replacing all filter media at once
  • Letting rock and driftwood soak before adding to soak up beneficial bacteria

Balancing populations of beneficial and potentially harmful bacteria is key to maintaining a healthy aquarium environment.


Controlling bacteria levels in an aquarium relies on finding the right balance between different organisms, nutrients, and tank maintenance practices. Relying on bacteria-eating fish, invertebrates, plants, and algae eaters as natural clean up crews is usually the most sustainable approach. This can be supplemented with equipment like UV sterilizers for the water column and occasional use of medications. The end goal is promoting healthy populations of beneficial bacteria while limiting uncontrolled growth of nuisance bacteria.

Maintaining stable, optimal water parameters through regular testing, partial water changes, and filter cleaning helps give the upper hand to beneficial bacteria and wanted tank inhabitants. Overall biodiversity, avoiding overstocking, and limiting food inputs prevents excess nutrients that can fuel nuisance bacterial blooms. Naturally maintaining balance between the different elements of the aquarium ecosystem is key to controlling bacteria.

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