Bio-filters: The need for an new comprehensive approach

The aquaculture industry struggles to profit in light of low product prices, increasing costs of inputs and constrains due to environmental, water and land limitations. Intensive aquaculture systems are relevant to efficiently produce fish and shrimp. The two important limiting factors of intensive aquaculture systems are water quality and economy. An intrinsic problem of these systems is the rapid accumulation of feed residues, organic matter and toxic inorganic nitrogen species. This cannot be avoided, since fish assimilate only 20-30% of feed nutrients. The rest is excreted and typically accumulates in the water. Often, the culture water is recycled through a series of special devices (mostly biofilters of different types), investing energy and maintenance to degrade the residues. The result is that adding to the expenses of purchasing feed, significant additional expenses are devoted to degrade and remove 2/3 of it. There is a vital need to change this vicious cycle. One example of an alternative approach is active suspension ponds (ASP), where the water treatment is based upon developing and controlling heterotrophic bacteria within the culture component. Feed nutrients are recycled, doubling the utilization of protein and raising feed utilization. Other alternatives, mostly based upon the operation of a water treatment/feed recycling component within the culture unit are discussed. The present paper was presented in the biofilter workshop held in Honolulu, 8-11 November 2004. The main purpose of this paper was to raise new ideas and new options toward the planning and operation of intensive fish/shrimp ponds. (c) 2005 Elsevier B.V. All fights reserved.