For some reasome the search feature is not working for me so i am going to ask this question and if it is a repeat maybe someone can send me to the right place.

For what i have been reading here and multiple other sites is that in a commercial system the fish are more or less a break even point as far as roi for the system. I am looking to build a backyard system to help feed my family and hopefully make enough to sell a little at farmers markets or to friends. Most people around here catch their own trout/bass/perch to eat so i imagine it could be hard to sell any edible fish.

Why is using koi not a valid option. Seems to me that some koi can sell for large sums of money even though it can take years to get there. I think not changing out fish as often would help keep the water balance in place. Am i totally missing the boat here? It seems so obvious to me that i must have it wrong.