Did a search and didn't get anywhere. Been thinking (yes my brain hurts!) but is anyone using a large body of water like a dam for a recirculating AP system? Can't see any reason it wouldn't work but I don't want to reinvent the wheel.
The dam nearest the house is biggish at approx. 13 mega litres (+/-5 olympic pools) and there is no way I could cycle all that water through grow beds once an hour!! But the nutrients are already there (via silvers, ducks, yabbies, turtles, children, etcetra) and the water level is reasonably constant due to being spring fed (varies approx. .5metre in level over the seasons). Power is at the dam wall, so pumping to grow beds that then drain back into the dam is simple. Any aeration and filtering of the dam water can only help the fish.
Problems?
Surface water temps are max 30C in summer and min 5C in winter, a thermocline at approx .7m down where the water feels like ice but should be approx 16C but will measure it (the year round earth temps are 16C 1m below the surface in this neck of the woods).
No idea of the pH, ammonia, nitrate/nitrite levels etcetera, but will measure. Obviously OK for Silver Perch, they went in as fingerlings 18 months ago and are now 300mm, so can't be too bad? Don't fancy trying to pH buffer 6 meg of water when the our soils are predominantly acidic (around 6.2).
Occassional flushing of system when it rains hard for more than a few hours - used to happen 6 times a year but the drought/climate change now means it happens once or twice a year. The spillway does not release fish as it has a baffle, but animal manures get washed in during heavy rains and would cause a nutrient spike. Fish have survived so far and the plants should like it?
The dam was origibnally very silty due to the yabbies (zero vis), but I suspect the Silvers have culled a lot of them as the vis/clarity has improved to approx 1.5m (got rid of the aquatic leeches too
). Silt could clog up the grow beds quickly?Anyway all thoughts appreciated, or pointing me to a thread that discusses same.
Cheers, MC
But the thinking is that by oxygenating the dam water a little by the return splashing, and some mixing of the otherwise still water, it should stir the system up a little anyway and the addition plants will become part of the additional activity.