The ND 21 is a hybrid between a female Nile tilapia (Oreochromis niloticus) of the ND-2 Tilapia family line and a male Blue tilapia (Oreochromis aureus ) of the ND-1 Tilapia family line.

Both the ND-2 Tilapia Oreochromis niloticus line and the ND-1 Oreochromis aureus line have been created by man through continuous selective breeding within the specific families.

ND21 tilapia comes with three main advantages:

• When a female Nile tilapia (Oreochromis niloticus) of the ND-2 Tilapia family line and a male Blue tilapia (Oreochromis aureus) of the ND-1 Tilapia family line breeds, the result is a batch containing no females at all. (There is however always a risk of foreign genetic material and the average proportion of males is therefore 98 percent.) By choosing ND 21 tilapia, there is no need for hormonal treatment to prevent uncontrolled breeding in the growing unit.
  
  
• ND21 tilapia grows fast. The growth rate is comparable to that of pure line Oreochromis niloticus. ND21 tilapia will grow somewhat faster in 22-25 °C (72-77 °F) and somewhat slower in 29-31 °C (84-88 °F).
  
  
• ND21 tilapia is more docile and less jumpy than Oreochromis niloticus. This is practical during all sorts of handling, e.g. sorting, harvesting and sampling.

When it comes to Streptococcus infection, ND21 tilapia has the same resilience as pure line Oreochromis niloticus.