Summer die-off - Need advice

[DTown]

Greetings everyone. I've been a member here for a while and do a lot of reading, but can't remember if I've ever even posted to the forum. I have an 850 gallon pond, about 2 feet deep at the deepest point. I have a waterfall and a 50 gallon filter, using water hyacinth as media during the summer. I feed the filter and waterfall with a 2400gph pump. I built the pond about 15 years ago, and added 4 fish the first and second years. From there, the population increased to about 40 fish a couple years later and stabilized at that level for a couple years. Soon after, the herons found my pond and removed about half of my fish. I added a net, and though the herons can't get to the fish any more, the fish population remained in the 20-25 range until this summer. That was fine with me. It was a minimal effort to keep the pond and watching the fish while sitting on the patio was great.

This summer, I started seeing floaters. First it was 1, Then a couple days later there were a couple more. Then another the next day. This kind of pattern continued for several weeks. I was distraught. I tested the water. No ammonia, no nitrates and no nitrites. pH 7.4. I even doubted that my water test kits were accurate, so I brought a sample to my fish store and had them test it. Same results. The water seemed to be fine. After the first few fish died, I took a closer look at the victims. I could see no ich, no parasites... checked their skin, mouths and gills. Nothing visible. I treated the pond with melafix, but that didn't seem to help. And so now, as my water lilies die back, I see that none of my fish remain.

(are you guys still with me? Thanks for reading this far!) So, my question is, what do I do this winter? Do I drain the pond and leave it empty over the winter? Do I drain it and then refill with fresh water now? In the spring? Do I do nothing and just put some more fish in in the spring? Your advice is appreciated.

Kind regards,

Dave Town

 

[Faebinder]

Did you add more fish a month before the die offs began?

 

[DTown]

Did you add more fish a month before the die offs began?

Nope, no additions for approximately 13 years.

 

[Faebinder]

Next question: Did you or your neighbors spray any insecticides or anti weed around the pond area?

 

[DTown]

Next question: Did you or your neighbors spray any insecticides or anti weed around the pond area?

Hmmm... hard for thins old brain to remember little details like that from so far back... but I'd say no, I didn't spray any insecticides... though there is a possibility that I used some weed killer... I use a spray (Weed-B-Gone) from time to time to control the rogue weeds. I am always careful around the pond though, and don't think that any of my weed control efforts made their way into the pond.

As for the neighbors... I'd have no idea. Both of the neighbors that are near the pond have fences up, and the pond is at least 10 or 12 feet from the nearest fence.

 

[sissy]

next question is do you have an aerator and do you test your water or can you take it to be tested and this way you may get a better reading . .A lack of oxygen and and poor water can kill fish .The biggest usually die first and first thing in the morning .Remember when the wind blows chemicals can blow for mile from the point of where they were realised .Also some cleaning stuff ,like when people ash there siding .

 

[DTown]

next question is do you have an aerator and do you test your water or can you take it to be tested and this way you may get a better reading . .A lack of oxygen and and poor water can kill fish .The biggest usually die first and first thing in the morning .Remember when the wind blows chemicals can blow for mile from the point of where they were realised .Also some cleaning stuff ,like when people ash there siding .

Thanks Sissy, that's interesting. I do have a waterfall, with about a 24" plunge into the main pond. I'm probably dumping 12-1500 gph over the falls. I also have a large air stone fed by a tetra luft pump. It runs 24x7x365. There are also 2 returns from the filter that have about an 8 or 12" fall into the pond, adding to the gas exchange. I have a 50 gallon filter full of hyacinth, and thicket of irises growing in the water, and about half the surface covered with lily pads. Should be enough oxygenation, I'd think. Especially considering that this summer was not nearly as hot as other summers have been, and I had no such issues in those years.

It really has me scratching my head, and kicking myself in the butt for not being able to figure it out.

Thanks for your time.

 

[sissy]

Plants use up oxygen at night and release it during the day .How I know about weed killers traveling for miles is that they spray it around the power towers about 2 to 3 miles from my house and people have lost plants trees and grass when they spray .I know when they are going to do it by the county news and i cover my pond just in case .> have 12 air stones and to bio filters with plants and I keep air stones in each filter .

 

[mrsclem]

I see so many threads started with the same pattern. I've had my pond for years and nothings changed! The one thing that is overlooked is that fish grow and reproduce! More fish and larger fish require more filtration. It seem like you are relying on your plants to filter your pond. Your water tests show a low ph.
How well netted is your pond? Can you account for all of the fish dying in the pond?

 

[DTown]

Plants use up oxygen at night and release it during the day .How I know about weed killers traveling for miles is that they spray it around the power towers about 2 to 3 miles from my house and people have lost plants trees and grass when they spray .I know when they are going to do it by the county news and i cover my pond just in case .> have 12 air stones and to bio filters with plants and I keep air stones in each filter .

Wow! I had no idea that weed killers could be so potent so far away from where they are sprayed. Amazing. On the weed killer note, do you think that if weed killer was an issue that I'd have had problems with my plants as well as my fish?

Thanks for your time.

D.T.

 

[sissy]

not always because there is a farm pond on the other side of my property and the epa was out here when they sprayed a year ago and killed trees and all the fish died in the pond and fish that were taken for testing showed the toxic poison and the water they took also showed it .Seems water vapors from the pond can draw in poisons or other stuff in the air .That was from the report from EPA .They have not sprayed since .Marty is tryiing to sue them for the loose of his farm pond .They spray the same stuff around railroad tracks and along highways but at a safer level,but still not safe enough .I have seen them spraying along the highways here . .That was all from the EPA .But if your pond is at it's capacity and filter cannot keep up fish will die off .

 

[DTown]

OK. so assuming that my water was contaminated with either a herbicide or an insecticide, what's your recommendation? Do I drain it and leave it empty for the winter? Do I drain and refill now? Do I drain and refill in the spring. My gut tells me to drain it down now, and refill it, so the water can stabilize over the winter, and the plants will remain alive and well for a good start next spring. What do you think?

Thanks again for your time.

D.T.

 

[Meyer Jordan]

If this had been herbicide/pesticide contamination the fish would all have died in a short period of time, not over several weeks. I suspect that as @mrsclem mentioned, you may have too little biofiltration. This may not be the direct cause of your fish die-off, but water quality is a definite factor in influencing the immune system in fish.
Do you have the numeric results of a recent water test?

 

[Faebinder]

Hmmm... hard for thins old brain to remember little details like that from so far back... but I'd say no, I didn't spray any insecticides... though there is a possibility that I used some weed killer... I use a spray (Weed-B-Gone) from time to time to control the rogue weeds. I am always careful around the pond though, and don't think that any of my weed control efforts made their way into the pond.

As for the neighbors... I'd have no idea. Both of the neighbors that are near the pond have fences up, and the pond is at least 10 or 12 feet from the nearest fence.

Spraying within 30 feet followed by a rainy or windy day may cause some overflow. In a pond these herbicides seem to kill silently.

I had a significant fish kill from some spraying near the pond x2 and both times it didn’t dawn on me till weeks later that the fish kill was related to it.

Did you spray intermittently such that fish died slowly.

 

[DTown]

If this had been herbicide/pesticide contamination the fish would all have died in a short period of time, not over several weeks. I suspect that as @mrsclem mentioned, you may have too little biofiltration. This may not be the direct cause of your fish die-off, but water quality is a definite factor in influencing the immune system in fish.
Do you have the numeric results of a recent water test?

Nitrates - 0
Nitrites - 0
Ammonia - 0
pH - 7.4