Pond Boss Forums INTRO Questions & Observations developing a spring?

Cecil,
When raising trout in tanks fed by spring water is temperature the major limiting factor? In a 1000 gallon tank the number I'm hearing for Tilapia is 500-600 pounds but they are a warm water fish and very tolerant. With a spring (too cold for tilapia) flowing at say 5 gpm, the water overturn rate should be around 3.33 hours, that should take care of the fish waste but in the summer sun, temperature may be the factor. I can understand how springs flowing into a pond can be so diluted that their effect on temperature in summer can be limited, but what about in tanks? any info, or good books to read on the subject. I'm setting up a system in a greenhouse for Tilapia and HSB but the spring sounds promising for trout and I'd deal with 50 to 75 pounds a year.