Bacto Fuel Bacillus and the Bacteria Behind Your Reef

Your reef has a busy community of bacteria living in its water, rock and sand. As food and waste move through the aquarium, these microbes change the forms of nutrients and return some material to the food web.

Bacto Fuels Bacillus is Planktura’s liquid bacterial supplement, containing four live cultures. To understand the science behind our interest in these bacteria, let’s look at nutrient cycling, mineral formation and the ways some bacteria interact with other microbes.

What is in the bottle.

The label lists Paenibacillus mucilaginosus, Priestia megaterium, Cytobacillus firmus and Bacillus amyloliquefaciens. The first part of each name identifies its genus. Three were formerly placed in Bacillus and have since been reclassified, which explains the older names in research papers.

Within a species, individual strains can also behave differently. Think of a strain as the particular version of a bacterium used in a study. [T1–T3]

Why these bacteria interest us.

Researchers have studied Paenibacillus mucilaginosus for mineral dissolution and for clumping particles together, a process called flocculation. Priestia megaterium has been investigated for phosphate release and nitrite processing. Studies of particular Bacillus amyloliquefaciens strains include nitrogen processing and production of antibacterial or antilarval compounds. A coral-derived bacterium identified as Cytobacillus firmus has also been investigated in coral disease research. [R1–R6,R13]

These studies help to explain our interest in the blend of bacteria.

Following nutrients through your reef.

Consider what happens to a little uneaten food. Bacteria break down organic compounds, use some nutrients to build new cells, and release others into the water. Those cells can themselves become food for other organisms. This movement and reuse of nutrients is part of nutrient cycling.

Inside many reef-building corals, symbiotic algae use light to make organic carbon compounds and pass some of that material to the coral animal. Bacterial recycling and photosynthesis both contribute to the reef’s food web. [R7,R8]

Recycling moves nutrients through the reef’s food web. To carry nutrient-containing material out of the aquarium, we also rely on export: water changes, harvested algae and waste collected by filtration.

Nutrient pathways: recycling, nitrification and export perform different jobs in a reef aquarium.

Where do the nutrients go? A conceptual guide to recycling, nitrification and export; arrows do not represent measured rates. [R7,R9]

The microbial loop and the nitrogen cycle.

In the microbial loop, dissolved organic material feeds bacteria and becomes part of their biomass. This biomass can then enter the food web when other organisms eat those bacteria. Aquarium cycling usually refers to establishing nitrification: ammonia is converted to nitrite and then nitrate by specialized microbes, including ammonia-oxidizing bacteria and archaea.

You can introduce an appropriate marine nitrifying starter or established biological media at the beginning of a fishless tank cycle. Establishing this microbial community helps the aquarium process waste throughout its life. [R9]

Denitrification is another pathway: microbes can convert nitrate or nitrite through a series of steps toward nitrogen gas, N₂. When that gas escapes into the air, nitrogen leaves the aquarium, which can lower nitrate levels in the tank. Taking nitrogen into new cells is a separate process.

Priestia megaterium is worth mentioning when we talk about denitrification. Researchers described an aquaculture-pond isolate as an aerobic denitrifier and reported about 92% nitrite-nitrogen removal in its laboratory screening test. Another study found that Bacillus amyloliquefaciens removed nitrite and some ammonia, although ammonia removal was poor at low starting concentrations. [R1,R2]

Phosphate is part of the story, too.

Phosphate deserves attention alongside nitrate because microbes also change how available phosphorus is to other organisms. Some bacteria release organic acids that help free phosphate attached to minerals. Enzymes called phosphatases can release phosphate from organic compounds. [R3,R7]

For example, a Bay of Bengal sediment study classified 9 of 41 cultured phosphate-solubilizing isolates—about 22%—as Bacillus. Reef research from the Gulf of Mannar also identified phosphate-mineralizing isolates reported as Bacillus megaterium, the older name for Priestia megaterium. [R3,R7]

Organic acids and phosphatases can release phosphate; export removes phosphorus from the aquarium.

Phosphate release makes phosphorus available in the water and can increase a test-kit reading. Removing it from the aquarium requires export. Conceptual diagram. [R3,R7]

Mineral formation and coral skeletons.

Some bacteria change the chemistry around them in ways that can encourage calcium carbonate crystals to form. Researchers call this biomineralization. In a marine-isolate study, Bacillus lentus CP28 used urease to break down urea; the resulting chemistry raised pH and encouraged calcite formation using calcium already present in the liquid. [R10]

Carbonic anhydrase is another enzyme made by living organisms, including some bacteria. It speeds the reversible conversion between carbon dioxide and bicarbonate, a dissolved form of inorganic carbon. Extracellular activity—activity outside bacterial cells—has been measured in some Bacillus isolates. In a separate study, researchers used carbonic anhydrases from Bacillus megaterium in engineered Bacillus subtilis and produced calcium carbonate minerals. [R11,R19]

This chemistry is relevant to coral skeletons. Corals use inorganic carbon to build them, and researchers have localized a coral carbonic anhydrase in the tissue responsible for calcification. It is an avenue worth studying for its possible effects on the local carbon chemistry available to a coral. [R20, R12]

What bacterial interactions and coral disease research can tell us.

Coral-associated bacteria are studied for compounds that affect other organisms. One paper reports antibacterial and antilarval compounds from a marine Bacillus amyloliquefaciens strain—activities affecting bacterial growth and larvae. [R13]

In a 2025 study, researchers tested a coral-derived isolate identified as Cytobacillus firmus by DNA sequencing. They first measured inhibition of disease-associated bacteria on laboratory plates, then treated living coral fragments with white syndrome in aquaria. The authors reported partial tissue recovery with the most promising isolate. Research like this helps explain our interest in including C. firmus in the blend. [R6]

Reef microbes inhabit water, stony coral compartments, hard surfaces and sand.

Reef microbes occupy water, hard surfaces, sand and several coral compartments. Habitat does not identify a microbe’s function. Conceptual diagram, not to scale. [R24–R26]

Research beyond the aquarium.

Researchers are also investigating Bacillus for natural antifouling compounds—substances that help prevent organisms from attaching to surfaces. In a 2022 Red Sea study, Tunkal and colleagues isolated Bacillus licheniformis MBR1 from a soft coral. Extracts from this bacterium inhibited biofilm-forming bacteria and reduced barnacle larval settlement in laboratory tests. These findings show how compounds produced by some Bacillus strains could help limit marine surface buildup. [R17]

Coral probiotic research has also shown promising results in reducing disease progression and mortality. In a 2023 laboratory study, researchers treated Montastraea cavernosa fragments affected by stony coral tissue loss disease with Pseudoalteromonas McH1-7. Over 21 days, disease progression stopped in 59.1% of treated fragments, and tissue loss progressed significantly more slowly overall than in untreated controls. Complete mortality was also lower: 31.8% in treated fragments compared with 59.1% in controls, with 22 fragments in each group.

The same study found encouraging preventive effects. Following a single treatment, all 12 pretreated fragments remained free of disease signs during a 21-day experiment involving contact with diseased coral. Four of 12 untreated fragments developed disease signs. Together, these findings demonstrate the potential of a specific coral-associated bacterium to help mitigate disease and prevent transmission under the tested conditions. [R16]

A later field study, including University of Florida researchers, tested McH1-7 on wild corals. Whole-colony treatment slowed tissue loss during 2.5 years of monitoring. [R14]

Using Bacto Fuel in your routine.

Follow the directions on your current bottle. The Bacto Fuel label says to shake well and dose 10 mL per 25 gallons into high flow, daily, weekly or as needed; refrigeration is not needed.

Record your starting conditions, dosing, feeding and maintenance. Watch nutrient trends, particularly nitrates, and livestock behavior, and keep circulation and aeration working. If the water clouds or livestock show distress, pause dosing and assess the aquarium.

Water-testing vials beside a notebook on a countertop — AI-generated editorial illustration.

Bacto Fuel introduces four live bacterial cultures to your reef-care routine. Understanding their scientific background helps us ask better questions, interpret what happens in the aquarium and keep good husbandry at the centre of the process.