Hello Paul, I have some questions.

The objective of the research is to remove P from the effluent from
rainbow trout ponds. What is the treated water for?

I'm not familiar with cold water fish culture. In warm water fish
culture, there is no criterion of phosphorus for water quality for
aquaculture. I have consulted the National Water Quality Criteria for
Aquaculture, J. S. Alabaster 1982 Water Quality Criteria For Freshwater
Fish published by FAO, and also Auburn University's Water Quality book.
I understand that rainbow trout culture is somewhat important in the
U.S.A. The largest rainbow trout farm is in Idaho. There are many cold
water springs there and the flowing rate of current is about 13,000
L/minute and the water temperature 14 degree C with high DO.

Ambient phosphorus concentrations in pond water are usually quite
low. P is introduced into ponds in fertilizers to stimulate
phytoplankton blooms, enhance the abundance of natural food organisms,
and promote greater aquacultural production.

It seems that there is no need to do this for rainbow trout in U.S. Am I
right?

Heavy phytoplankton blooms can absorb large amounts of P. Much P
will, however, be absorbed by the pond soil. Even that P initially
absorbed by the phytoplankton will eventually be mineralized from
organic matter and enter the pond soil. Is the rainbow trout pond an
earthen pond or a cement pond?

>The triangle filter is able to remove about 80% of the P excreted
>by the fish with the biosolids, leaving about 20% of the P in
>the effluent.

 I'm interested in this. Could you explain it in detail?

Li Kangmin
Asian Pac Regional R & T Center
For Integrated Fish Farming, Wuxi 214081 China