I sent an email to Alan Johnson, as suggested above. Here was his response:
"Dear Mr Perrin,
To write a response to your question about stocking tilapia into your farm pond in Iowa to control filamentous algae I have consulted Fisheries Chief Joe Larscheid and my supervisor Jay Rudacille. We understand the temperature tolerance of tilapia. However Joe stated that stocking tilapia into Iowa’s waters will not be allowed under any condition.
There is a lack of scientific data on the effects of tilapia as a management tool for farm ponds. Digestion of the filamentous algae will release the nutrients bound in them, likely causing more single-celled algae to bloom causing water to become green. Tilapia may diminish the filamentous algae then turn to other food sources which could compete with the other game fish in the pond, example would be consumption of zooplankton important to larval bass and bluegill. If the tilapia did result in a population of large bass, when the tilapia die there would be no forage until tilapia are restocked and spawn again.
Use of the bass and bluegill system with removal of bluegill by angling can result in the large bass you seek. Contact your local fisheries biologist to discuss pond management techniques further.
Sincerely,
Alan
J. Alan Johnson | Natural Resource Biologist
Iowa Department of Natural Resources
P 641-647-2658 | F 641-647-2690 | 15053 Hatchery Place, Moravia, IA 52571
www.iowadnr.gov"
