Fathead minnow baitfish raised in ponds adjacent to channel catfish ponds will eat zooplankton that thrive on catfish waste. Growers simply circulate the water between the two ponds to put this environmentally friendly waste-disposal system into action. ARS scientists found that the two-pond system increases catfish production while reducing minnow production costs. Accumulated fish waste and uneaten feed now frequently limit farm-raised channel catfish production. That's because as the waste and feed decay, the decaying process uses up oxygen in the pond, creating an unhealthy environment for the fish.
Circulation helps increase oxygen levels in the water.
Also, the wastewater pumped into the minnow pond provides nutrients to enrich the zooplankton on which minnows feed. Copper sulfate, known to cut algae growth in ponds and protect fish against external parasites, won't leave unwanted copper in the fish's flesh. In a 4-year laboratory study for the U.S. Food and Drug Administration, ARS scientists found edible fish flesh contained no extra copper after ponds were treated with copper sulfate. The research also showed that copper concentrations in fish liver returned to normal levels within 8 weeks. Copper sulfate has been approved by the U.S. Environmental Protection Agency as a herbicide to fight algae.