Biofloc Carbon & Balance C:N, Beat Ammonia

Biofloc is a fish or shrimp farming method that grows a dense community of beneficial bacteria and microbes in the water. By keeping the carbon-to-nitrogen (C:N) ratio high, these microbes take up toxic ammonia released by the animals and turn it into microbial protein — which the fish and shrimp then eat. It cleans the water and recycles waste into feed.

First estimate the ammonia nitrogen produced from feed (feed × protein × the nitrogen and excretion fractions). Then the carbohydrate needed = ammonia N × the carbon required per unit nitrogen to reach the target C:N, divided by the carbon content of the source (molasses is roughly 50% carbon). The tool returns the carbon source — usually molasses — to add per day.

The C:N ratio is the balance of available carbon to nitrogen in the water. Heterotrophic bacteria need plenty of carbon to assimilate nitrogen (ammonia) into their cells. A target C:N of about 12–20:1 drives them to consume ammonia rather than letting it accumulate, so adding a carbohydrate source raises carbon and locks up the nitrogen as floc protein.

Molasses is cheap, readily available, dissolves easily and is rapidly used by bacteria, making it the most common biofloc carbon source. Other options include sugar, jaggery, wheat flour, rice bran or tapioca. They differ in carbon content and how fast microbes use them; molasses at roughly 50% carbon is the standard reference the calculator uses.

Total ammonia nitrogen (TAN) building above roughly 1 mg/L — and especially the toxic un-ionised fraction at high pH and temperature — stresses fish and shrimp, harming gills, growth and survival. The whole point of biofloc carbon dosing is to keep ammonia from accumulating by feeding the microbes enough carbon to consume it as it is produced.

Typically the calculated carbohydrate is added daily, often split through the day or after feeding, and dissolved before adding so it disperses. Monitor TAN and nitrite, floc volume (Imhoff cone) and dissolved oxygen, and fine-tune the dose — more carbon when ammonia rises, less as the mature floc community stabilises water quality.

Yes — the C:N balance principle is the same for tilapia, catfish, carp and shrimp (vannamei). Just enter the feed amount, the feed's crude protein and your target C:N, and the tool gives the carbon source to add. Stocking density, aeration and floc management differ by species, but the carbon dosing maths is universal.

Yes — biofloc is oxygen-hungry because the microbial community and animals both consume it, so continuous strong aeration is essential. Biofloc reduces but does not always eliminate water exchange; you still manage solids (settling), pH and alkalinity. Carbon dosing controls nitrogen, but aeration and solids management keep the system healthy.

They're solid planning doses. Actual carbon demand shifts with floc maturity, temperature, the real protein and excretion of your feed, and the exact carbon content of your molasses batch. Start with the calculated dose, watch ammonia and nitrite closely in the first weeks, and adjust — biofloc carbon dosing is steered by water-quality readings, not set once.