how to produce fish feed pellets with a proper density?
Fish digestive system is very short (for example: it is 10 times shorter that swine digestive system) and that is why fish feed must be light. Both dimensions and shape of fish feed pellets must be adjusted to size of fish. Besides, in water pellets must behave according to habits of fish: sink or float on surface of water. And this feature of feed depends on pellet density.
Kinds of feed pellets for fish
Depending on product density we can get food with different properties, which are appropriate for their nourish habits, which are explained below:
• food floating on surface of water – for warmwater fish
• slowly sinking food – for raptorial fish, which like cold water
• sinking food, water resistant, for warmwater fish
• sinking food, extremely water resistant, for shrimps and other crustaceansIn growth phase fish can need pellet up to 12 different sizes, from 0.05 mm to 12 mm. If the given food is too big or too small, fish will not eat it.
Fish feed pellets production process
On density (specific weight) depends if pellet will float on surface of water or will sink. Floating pellets have the specific weight about 450-550 g/dm3, and sinking pellets – 550-650 g/dm3. Before pelleting (or expansion) components must be conditioned (mixed) with use of steam and water.Conditioning temperature is 80 – 90oC, content of moisture in mixture directly before pelleting is 15-16%, if expander will be used then 18-20%, and if extruder will be used then 25-30%.Fish feed extruderThe wet type fish feed extruder equipped with heating and cooling system was newly developed, with which we can adjust the expansion and control the temperature as well as density of the product. If we compare pellets produced in 3 different production processes, it will appear that the food made using extruder sinks 50% slower than food produced only with normal pellet mill.
The density can be modified by adding a kind of oil to formula. Depending on amount of added oil the food will float or sink and density of mixture produced basing on the same formula can be modified, so that it can have density from 430 – 550 g/l.Final conclusionsThe condition of a proper fish breeding is adjusting of the density of pellet to nourish habits of individual species. Choosing the proper density of pellets we will save on cost of feeding and avoid exceeding pollution of water. Food producer can adjust the density of fodder using fish feed machine, and due do proper conditions of raw materials treatment.