Other feed inputs to aquaculture are derived from terrestrial agriculture or, in the case of ®lter-feeding molluscs, from planktonic production. Pelagic and benthic microalgae are also consumed directly by herbivorous and omnivorous carp and tilapias and are thus important in extensive and semi-intensive freshwater ponds common in the tropics. Mollusc farming and other extensive aquaculture do not use compound feeds and do not therefore appropriate fisheries production directly.