E.4.0 | Protocols and Tables (Grow Out) : Batch Systems

Dose for Biomass (or Million Rotifers) in the Culture Tank

Feed rate is determined by the Wet Weight Biomass of rotifers in the tank at the time of feeding. For Batch Systems it is often more convenient to use rotifer count, standardized by the size of the rotifer, as a proxy for mass. Feed rate per gram (or million rotifers) can be adjusted to increase or decrease the rate at which the rotifers grow (doubling time).However, in the end, the mass of rotifers harvested is directly proportional to the amount of feed used.

Table E.5: Feed per hour per 100 million rotifer at a growth rates of 80% per day, Adjusted for rotifer Lorica length


  • Feed Rate is based on count (biomass) at the beginning of the day. To change the rate at which the rotifers grow, adjust feed proportionally. Example: to grow RMI Mini-L 160 rotifers on RotiGrow Plus at 60% growth per day instead of 80% growth per day, multiply the above feed rate (12.7 ml per 100 million rotifers per hours) X (60%/80%) = 8.5ml per 100 million rotifers per hour. You will use less feed per day, but it will take longer to produce the desires mass of rotifers. The change in feed rate is proportional because the net feed conversion rate is constant.

Table E.6: Typical feeding application using RotiGrow Plus and feeding at a rate that produces 80% growth for RMI

Wet weight is easily obtained by screening the whole or a small percentage of your culture and blotting the bottom of the screen with a paper towel to remove excess moisture. If you know the number of rotifers you need to harvest and their size, but not their wet weight biomass, use the Lorica Length to Biomass Calculator (Table 6.2) repeated below.

Table E.7: Rotifer length to mass conversion

a. These numbers are mathematical approximations using the RMI “Mini-L 160” as the base data point. Actual numbers will vary depending on rotifer shape (thin vs. plump) and composition (density).
b. Rotifer length is measured as the distance between the anterior tip if the lorica with the corona retracted and the base of the foot. Rotifers retract their corona when fixed with formalin.
c. Better data can be obtained by screening a liter of rotifer culture and dividing the weight by the number of rotifers in the liter of culture.

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