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Table 3: Rules of thumb for NFT in aquaponics
Rules of Thumb for Nutrient Film Technique in Aquaponics
Substrate Characteristics• Channels can be made from pre-fabricated plastic, rain gutter material, or PVC pipe • White pipes should be used as they reflect sunlight keeping the inner channel cool
System Design• Square or rounds channels are suitable • Channel diameter should be appropriate for the crop's root size • Leafy greens - 7.5 cm pipe diameter • Fruiting crops - 11 cm pipe diameter • Channels should not exceed 12 m to avoid nutrient deficiencies in plants at the end of the pipe • Slope of channel need to be 1 cm/m to ensure an adequate flow • Efficient solids filtration required as solids can clog tubes • Heavy aeration required
Carrying Capacity• High fish stocking density of 60kg/m3 (0.5 lb/gallon) can be achieved with appropriate solids and biological filtration\n• Plant need a minimum of 21 cm between
Water Flow Management• 1-4 hour water retention time in plant troughs • Long, narrow beds help water move through the system
Maintenance• Channels need to be cleaned between harvest • Back up pumps and generators are needed as plants are very vulnerable during outages
*Exception is in early life stages where fish can consume 5-10% of their body weight in food per day.
Sump
The sump is the lowest point of the system and where water collects to be distributed as needed throughout the system. Water quality samples can be taken here and amendments can be made without overwhelming the fish or hydroponic components. While not a requirement, the addition of a sump prevents the water level from changing in either the fish tank or hydroponic component. In other cases where safeguards are put in place, the fish tank or hydroponic component can be used as the sump.