pheromones, hormones are still not removed by plants or nitrification. have you all done any comparisons of growth of fish in open systems versus closed systems I have seen stunted tilapia M. i will not be using tilapia in my system but KOI. Tilapia would never cover their cost, much less the labor in raising them in a 20,000 gal system with the cost of utilities and such in the SF Bay area, which in a decent economy KOI will. (although we know the economy is getting much worse) i know that in third world countries tilapia are used as part of their bio waste water treatment systems, i never buy imported tilapia or at a restauarant.
certainly not trying to be negative by any means, i always feel a responsibility to whatever i am raising to afford it the best that i can within reason.

thanks for all of the information. i have garnered a lot from this forum in the short time that i have been a member.

Rich