1. Ngo Van Hai, BSc, Can Tho Univ, VN; MSc, AIT, Thailand; PhD, Curtin Univ of Tech, Aus. Email: ngovanhai@yahoo.com Minh Hai Sub-Institute for Fisheries Research PROMOTION OF NATURAL FOOD ORGANISMS THROUGH FERTILIZATION AND WATER QUALITY MANAGEMENT IN FISH PONDS

2. Introduction Role of natural food How to promote the natural food Other businesses Outline

4. nutrients detritus Fish pond ecosystem

5. = small phytoplankton = large phytoplankton = small zooplankton = large zooplankton = benthos

7. Life cycle of micro-orgamisms

8. detritus nutrients Increasing fish production fish density feeds $$ costs Inorganic fertilizers Organic fertilizers Oxygen

12. organic wastes feeds food food fertilizers autotrophic & heterotrophic food webs Fish Within a pond

13. 3. How to promote the natural food in fishponds

19. b. Chemical fertilizers Fertilizer programs: not developed, site dependant Commercial fertilizers: Urea (N 2 H 4 CO), N-P-K (46-0-0), ammonium phosphate N-P-K =16-20-0, superphosphate N-P-K =16-16-16 Fertilization enhances production: 1 to 8 times Divide into small amounts Dissolve fertilisers with water then scatter equally to water surface at morning. Apply at the beginning, when phytoplankton dies off, exchange water, WQ

26. Appetite/satiation Feeding behaviour Feeding habits Feeding frequency Feeding ratio Complete feed ( Crystal waste/faeces as solid waste) d. Feeding regime

27. 6CO 2 + 6H 2 O + light energy C 6 H 12 O 6 + 6O 2 C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + heat energy Time DO (mg/L) 2-4 pm 2-4 pm 3-4 am

40. Nutrients : Fertilisers (organics and inorganics) Food and waste CO 2 : atmosphere, respiration of organisms, alkalinity, lime, CO 2 bottles Sunlight : adequate penetration of sunlight (aeration and exchange water) Maintain healthy bloom

41. $$