BIOFloc Blog

What is Nitrification Process in BIOFloc?

It is the biological nitrification process of breaking down Ammonia into Nitrate. When we give Nitrogenous sources in the form of Fish Feed or Fish Excretas into the pond, it decomposes and produces organic sludges in the bottom of the pond. Ammonia and Ammonia Ions are produced from sludges. Excess ammonia creation inside the pond may kill the fish if it is not controlled. Controlling the Ammonia in aquaculture is called Nitrification Process. Let’s discuss how the nitrification process works.

In the Nitrification Process, the Total Ammonia Nitrogen (NH3 + NH4+) gets Oxidized and form Nitrite (NO2–) then again Oxidized and converted into Nitrate (NO3).

The bacteria which converts Total Ammonia Nitrogen into Nitrite (NO2–) is called Ammonia Oxidizing Bacteria (AOB). These AOB are also known as Nitrosomonas Bacterias.

The bacteria which converts Total Nitrite (NO2–) into Nitrate (NO3) is called Nitrite Oxidizing Bacteria (NOB). These NOB are also known as Nitrobacter Bacterias.

Between Nitrite and Nitrate, Nitrite is more harmful to the fish as it enters into the body and affects the immune and blood circulatory system and fish get killed.

So these Nitrosomonas and Nitrobacter Bacterias are used to remove harmful ammonia from the system.

But mostly in Biofloc System, Heterotrophic Bacteria are used to remove ammonia and convert undigested feed into micro-bacteria protein, which is known as FLOCS. These flocs again are eaten by fishes, which helps to lower down the FCR.

What is Carbon to Nitrogen Ratio i.e. CN Ratio in BIOFloc

Carbon to Nitrogen Ratio (CN Ratio) is a process of controlling the amount of Nitrogen in water. Most popular CN ratios are 10:1 and 15:1, which means in CN Ratio 10:1, you need 10 Carbon Sources to kill 1 Nitrogen. In aquaculture, CN Ratio is calculated based on Protein Percentage of Feed and Total Ammonia Nitrogen (TAN)

CN Ratio with Zero Water Exchange

The CN Ratio Calculation is based on Fish Feed Protein Percentage and the below chart shows the CN Ratio of the feed materials.

Protein Percentage (%)       CN Ratio

• 15                                             21.5
• 20                                            16.1
• 25                                            12.9
• 30                                           10.8
• 35                                            9.2
• 40                                            8.1

If you are using 30% protein feed then according to the above chart the CN Ratio of 10:1 is fulfilling. As per the studies, the CN Ratio of 10:1 and 15:1 are more successful. It has been proved the CN Ratio of 10:1 does not require even water exchange.

In a BIOFloc system, it’s recommended to feed low protein feeds. You will have better control over Ammonia and the mortality rate will be less.

Here is an example;

Let’s say the tank contents 100kg of fish biomass and you are feeding 4% of the bodyweight which equals to 4kg feed (4000 grams of feed)

The feed is made up of with Carbohydrates Proteins

Let’s calculate Carbohydrates in feed;

4000 grams of feed contents 90% of dry matter i.e. 3600 gram and 10% moisture i.e. 400 grams on it

Out of 90% of dry matter i.e. 3600 grams, 70% get wasted i.e. 2520 gram and only 30% get digested by fish

For C:N Ratio calculation, you need to consider 70% waste i.e. 2520 gram, because this 70 % of waste is responsible for creating ammonia inside the tank. Don’t calculate CN ratio on the basis of total feed given to fish i.e. 4000 grams.

It’s known that feed contents 50% of carbon in it. So, 1260 grams of Carbon can be found on 70% of waste feed i.e. 2520 grams.

So every day you are adding 1260 grams of Carbon into the water.

The feed that we are using here contents 30% of protein i.e. 30% of 2520 = 756 gram

In 756 gram of protein, Nitrogen contents 16% = 120.96 gram (N)

If you are using BIOFloc in a proper and scientific way then you no need to add Carbon into the tank. 

If you look at the C:N Ratio value its 1260:120.96 which is 10:1 ratio.

C:N Ratio 10:1 = 120.96 x 10 = 1209.6 gram

We already have Carbon of 1260 gram = 1209.6 – 1260= (-50.4) gram – Zero Carbon needed

C:N Ratio 12:1 = 120.96 x 12 = 1451.52 gram

We already have Carbon of 1260 gram = 1451.52 – 1260=191.52 gram Carbon needed

C:N Ratio 15:1 = 120.96 x 15 = 1814.4 gram

We already have Carbon of 1260 gram = 1814.4 – 1260=554.4 gram Carbon needed

Now let’s calculate how much carbohydrate is required to neutralize the Nitrogen.

• Sugar Contents = 42% Carbon 
• Molasses Contents = 22% Carbon

In 1kg Sugar, you will get 420 gram of Carbon & in 1kg of Molasses it will be 220 gram of Carbon

For maintaining C:N Ratio of 12:1, you need 191.52 gram of Carbon

• You need Carbohydrate (Sugar) = approximately 460 grams
• You need Carbohydrate (Molasses) = approximately 870 grams

 

C N Ratio Based on Total Ammonia Nitrogen (TAN)

Let’s consider the Total Ammonia Nitrogen (TAN) in the BIOFloc Tank is 2 PPM (Parts Per Million or Milligram Per Liter)

For a 10,000 Liter Tank it will be 10,000 x 2 = 20,000 mg TAN

Lets convert mg to gram = 20000 mg / 1000 = 20 g TAN

• For C:N Ratio 10:1 = 10 x 20 = 200 gram Carbon needed
• For C:N Ratio 12:1 = 12 x 20 = 240 gram Carbon needed
• For C:N Ratio 15:1 = 15 x 20 = 300 gram Carbon needed (add 615gm sugar or 1230gm molasses)

Notes: 

• It’s already proved that C:N Ratio 10:1 and 15:1 are more successful than others
• Never add Carbohydrates all at a time, it may reduce the DO level
• Maintaining 20:1 Ratio will require more Carbohydrates that will add more cost to your project

 

How to Control Ammonia when C:N Ratio is 15:1

• 8 ppm Ammonia 10,000L Water = Add 2 Kg 460gm Sugar & Double for Molasses
• 4 ppm Ammonia 10,000L Water = Add 1 Kg 230gm Sugar & Double for Molasses
• 2 ppm Ammonia 10,000L Water = Add 615gm Sugar & Double for Molasses
• 1 ppm Ammonia 10,000L Water = Add 300gm Sugar & Double for Molasses
• 0.5 ppm Ammonia 10,000L Water = Add 200gm Sugar & Double for Molasses
• 0.03gm Sugar or 0.06gm Molasses required to manage 1ppm of Ammonia in 1 Liter Water
• 0.45gm Sugar or 0.90gm Molasses required to manage 1ppm of Ammonia in 15 Liter Water
• 1.74gm Sugar or 3.48gm Molasses required to manage 1ppm of Ammonia in 58 Liter Water

 

Final Words

BIOFloc system can be successful if you understand how to control Ammonia using an appropriate Carbon Nitrogen Ratio (CN Ratio). Its technology-based farming, failure of maintaining single criteria can create havoc in the BIOFloc System. Before you start your own BIOFloc Fish Farming, understand what is BIOFloc and how it works.