Hi Everyone, we have .35 acre, 8’ deep old quarry in which we swim. It is inundated with goldfish. The bottom is covered in sand and silt, goldfish waste.Hence, The water is extremely murky. We installed bottom aerators, which I now realize is creating more of a mess. In other words, the aeration stirs up the pond bottom (fish waste, silt, muck etc) What are your thoughts re getting trout, sunfish and bass to deal with the goldfish? We have been keeping aerators on all day. How many hours per day should we keep the aerators on? I was also told to ditch the bottom aerators and replace with top or fountain style aerators. Which would be very expensive as the bottom aerators were expensive. Thank you for your thoughts and comments.
If you can pull the diffusers up and put a plate/can/metal or plastic sheet* underneath them, and then replace them, you should be able to avoid having the bubbles stir up bottom sediment. They would still be below 99% of the water column, so they will still add oxygen to help decompose the goldfish poop.
Surface aeration probably won't get oxygen down to the bottom as well as bottom diffusers.
If you are not worried about fish health (which can call for different aeration hours depending on several factors), I'd guess all day long is best for the purpose of aiding decomposition on the bottom.
*I have used a non-functional stove exhaust hood for this purpose.
"Live like you'll die tomorrow, but manage your grass like you'll live forever." -S. M. Stirling
For a .35 acre 8' deep pond that is overrun with goldfish, I'd find someone in your area that has an aquatic applicators license and have them apply Rotenone to the pond to kill all the goldfish, then start over with the fish that you want. Once the goldfish are gone the issues that you have with the bottom diffusers should go away after the aerobic bacteria gets to working on the organic sediment. I agree with Theo, raise the diffusers 4" or so up off the bottom and your issues should go away once the goldfish are gone.
Over abundant goldfish(GF) are notorious for making the water turbid in the visibility of 12" - 16" or less. Once GF are over crowded and as adults (8"-12"),,, IMO no predator will ever be able to get them back to low density where the water has clarity of 1.5 to 2 meters or more. If it were mine, I would eradicate all the fish and start over or you will fight overcrowded GF with lots of frustration for many years.
Last edited by Bill Cody; 09/20/2307:06 PM.
aka Pond Doctor & Dr. Perca Read Pond Boss Magazine - America's Journal of Pond Management
If there are no other desirable or hard to replace fish in the pond except goldfish and you are OK with killing the other smaller critters (water bugs, insects, nymphs, etc) it is very cheap to apply the common nerve toxin bifenthrin used to kill mosquitos. In the US it is easy to buy on Amazon without a license. At pretty low concentrations it is a selective poison for goldfish (basically carp) You would have to be prepared to use a boat to net out hundreds of dead and floating carp/goldfish and of course you may not be certain you killed them all. You could do a few applications and slowly increase the dose till you are satisfied. Your experience may vary although there are studies in the past using bifenthrin as a selective goldfish poison with fairly good results.
Rotenone is more selective for fish of all types (but not selective for goldfish) but will save the smaller critters in the food chain.
I thought the water had a pretty bloom but still wonder if the green water is what she meant by murky. If most of visibility is hampered by the bloom and if nutrients are the problem it may change the approach. First I wonder if the goldfish may be there on account of having past FA blooms. IOWs, with the goldfish gone will the water clear and then grow FA? Might be worth while to treat with alum after eradicating goldfish. Second, I wonder whether it should be aerated in the summer. An anoxic layer will slow decomposition and thus slow the recycling of nutrients during summer when the water is desired to be clear. The aeration could be turned when too cold for swimming. Perhaps this might encourage a bloom with remaining/accumulated nutrients ... which can be treated. Maybe something like that annual if nutrients are a problem for the murkiness.
I really like canyon's idea of netting the fish as they die. This is good way to be sure the nutrients sequestered in the fish don't wind up returning to the water.
Finally, after removing the gold fish some other fish should take their place to control insects and mosquitos and such. Could SMB alone work to do that?
It isn't what we don't know that gives us trouble, it's what we know that ain't so - Will Rogers