Ok, so here's the thing..
For those of you who do not know me well, I have been doing this for long enough to know what parameters I should have with respect to the fish and the system itself. It wasn't so much a question that I posed, but rather a statement of facts which came about thru the process of raising catfish after raising what I consider to be a much cleaner fish- tilapia- for many years.
1. Yes, this is my underground tank, however it is coated with a food grade potable water coating- so that is not a problem.
2. Yes, I am feeding them the same type of products as when I only had tilapia, so no difference there.
3. Yes, I pretty much grow similar items thru out the seasons just changing the variety, so there was no real change in that aspect.
4. The tilapia had no change in growth or habit when they were present.
5. The system is stationary so there is no change with regard to sunlight, etc.
6. No, I do not believe they had less waste for the amount of food they ate- and Yes, they did eat a lot and grew faster than the talapia so there should not have been a shortage of food for the plants-
However, my observation when there was only catfish was that there were some definite changes to the plants with respect to growth as well as production of fruit and the need for additional nutrients that had to be added over the norm we had set for the past 6+ years in growing talapia.
The water in the system permeated the smell of catfish slime, though the water quality was always right on the mark. Even when the system was down to only 6 catfish when we were clearing it for the next batch of tilapia- the smell was still present.
In addition to these observations, the flavor of catfish is just that- there is no change with water quality or food quality- while on the other hand we gladly eat our tilapia cevechi style any day of the week- the flavor is superb and nothing like that of market fish.
Take it for what you will- I won't be growing catfish again if I can help it.