It’s the oxygenation, stup... Let me rephrase. In a closed ecological system with dynamic nutrient inputs, oxygen quickly becomes a limiting factor in the overall health and balance of the system. This is especially true when what you are trying to culture is dependent on oxygen to live (and thrive). Maybe the lights were unnecessary. But if you are going through all the trouble to (hand) dig 160 feet of ditch for buried cable and assemble, wire, float and anchor an aerating fountain, might as well go for broke (literally). It wasn’t THAT expensive. However, counting the price of the pond, fish, fountain, and feed we would probably much better off buying catfish at the local seafood house. Of course, we wouldn’t know where they came from and they would not be as fresh and I couldn’t witness the joy of my spouse as she catches one after the other, which I happily take off the hook and drop into the bucket (and later into the fry basket).
I’ve learned a lot about fish farming. Maybe I take it too seriously (lights excluded), but once I have committed to raising something, I start to worry about whether I have considered all the aspects and am doing what is necessary to ensure success. I hate to fail, though I have on many occasions. But I am in particularly adverse to the stinky evidence of fish farming gone bad. I blame it partly on the fish hatchery guy. I really only wanted a reasonable amount of fish for our half-acre pond, 400 hybrid bream and 150 channel catfish. In cavalier fashion, the fish guy ensured me that 1000 fish can easily be raised in a half acre pond and, besides, fish by the thousand would be much cheaper per fish than buying less. I should have known from the outset that this guy was fast and loose. After I carefully filled clean ice chests with water adjusted to pond temperature, bringing a thermometer with me to ensure no shock to the fry from the hatchery truck tanks, the guy just sticks his hand in the ice chests and says, “That’s close enough!” So now I have 1000 dependents that I can’t declare on my taxes. No way am I going to let them down, nothing too good for them. And all was well until Spring when they started to eat more and grow more and excrete more and now I am watching the pond go through textbook water quality changes. From turbid (adjusted with lime), to clear and pretty, to cloudy again (nitrophilous bacteria converting ammonia to nitrate) to matted floating filamentous algae – yuk, to now a healthy dark green (suspended algae) thanks to the fountain, the physical raking of the filamentous algae, the dry peroxide, and the application of pond microbes (the aqua-sphere Thais referred to). I’m not imagining that I am out-of-the-water on this so to speak, but I am happy with the results and you can indeed raise 1000 fish in a half-acre pond, but it takes a much greater degree of attention than it might otherwise. For those who have farm ponds or are considering them, the best publications I have found that can be accessed on-line are from the Southern Region Aquaculture Center of the USDA Cooperative State Research, Education, and Extension Service at http://srac.tamu.edu/index.cfm?catid=25