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Rotifers belong to a huge family , the main specie of rotifer that is cultured for feeding marine fish larvae is Brachionus plicatilis. Rotifers under favourable conditions reproduce at an incredible rate, each female will have severn daughters and with in eighteen hours those daughters will also have severn each. The only time when rotifers dont reproduce asexually is when conditions deteriate, they will then produce resting cysts which will have some males, when conditions improve the whole cycle starts all over again.
Rotifers have little food value but when enriched with algae they provide the perfect first food for many demersal spawning marine fish such as clownfish.Rotifers can take a wide range of salinities providing it is gradual, they are really a brackish organism but highly flexible in their requirements. Gentle aeration is required as the population will accelerate under ideal conditions irrespective of harvesting and enriching, however the biggest cause of a rotifer crash is ammonia.
There are thousands of different photosynthesising algaes that help to convert the carbon dioxide into oxygen, infact over half of our oxygen comes from marine plant life and the billions of algal cells. These algal cells are incredibly important, not only by producing oxygen but also as the food source at the the bottom of the food chain.Some algaes have motile cells where as others drift in the currents.They also come in many colours, green, yellow, brown etc.
Some algaes have been identified and processed for human and animal consumption, others have been identified and cultured for shell fish and other food aquaculture operations and some for ornamental fish aquaculture, in particular nannochloropsis oculata which is particulary beneficial with Highly unsaturated fatty acids, (HUFA). Others such as tetraselmis , isochrysis galbana are also some times cultured although isochrysis is more suitable for shellfish production and for healthy cultures the addition of Co2. is also needed. Plankton suppliers also sell concentrated algaes that contain a number of varieties for those who dont wish to have the bother of culturing but need to enrich the food organisms for the marine larvae.
Algal cultures can be purchased in liquid form or as algal discs, instructions will be included with the discs, they can provide a convenient method for those who only wish to produce algae when needed periodically.
Algaes are cultured with light, aeration and fertiliser, the vessels need to be sterile before use and well away from any rotifer cultures, takes only one rotifer and her daughters'daughters to completely consume a culture. The aeration should be quite strong but not violent and a good light source. The culture will turn darker and deeper in colour, when the culture has peaked, reached maximum cell density it will need to be used , leaving a small amount to seed a new culture, for use in breeding a batch system will need to be in operation with cultures peaking daily for rotifer enriching.