My entire population of gold fish died overnight, only one survivor found so far

[miamicuse]

I have a natural pond with over 20 gold fish, there are all kinds of critters in it, frogs, toads, crabs, I don't feed the fish they survive on their own. When I bought the property 2 years ago, it had 4 fish about 4-6 inches long. Since then more babies, and the babies grew up, and more babies, and eventually last I counted over 20 fish large (12+ inches) and small (2 inches).

Today I came home and I saw many fish dead, floating on water. I counted one survivor, but I am not totally sure because there may be more survivors hiding under the wood bridge.

I started to pick up the dead fish with a net and most of the dead bodies I do not see any damage. There are two to three with missing fins and tails but I saw a crab feasting on one when I pulled it out. I am trying to figure out what happened. Here are some pictures.

So far I pulled out 22 dead fish.

Any way to determine what happened? Is it some intruder - feral cat, raccoon, possum gone wild? Some sort of bacteria infection that killed them? Or over population lack of oxygen, or some toxin got into the pond?

They looked normal last night, and this afternoon all gone.

 

[cas]

So sorry to hear about your fish loss. Maybe one of the below happened?

POSSIBLE CAUSE-REASON

High ammonia or nitrite levels – not enough good bacteria to process ammonia/nitrite​

Chlorine-Too much tap water / well water added and no water conditioner used​

Low dissolved oxygen levels-Too many plants in pond, not enough surface area open, not enough aeration​

PH crash-Pond water is not buffered – KH is low​

Electrocution-Faulty wiring in pump, lights, etc.​

Toxins in the water due to lawn run off​

Toxins in the water due to sprays - City spraying for mosquito control, neighbors spraying for weeds/insects​

Toxins in the water due to rain- any large burns or industrial activity in the area that could contaminate the rain​

Toxins in the water from ornaments added to pond-Chemicals seeping from ornament​

Toxins from tree trimming Oil spray from chain saw, poisonous saw dust into water (Jacaranda tree –koiphen) NOTE: Oak sawdust will kill grass and vegetation.​

Toxic water from performing treatments 1) Over or under dosing for size of pond 2) high Ph-salted pond water and formalin.​

Arsenic poisoning, Toxins from treated lumber Treated lumber used for a bridge over pond, toxins seep into pond when it rains​

Summer heat- Sun + shallow water = heat = low oxygen levels​

 

[Jhn]

Any way to determine what happened

Start trying to eliminate things. Easiest is Get a test kit and test the water, as @cas mentioned for ammonia, nitrite, nitrate, kh, ph, etc. The numbers may provide an obvious answer.

Also, to add to @cas low oxygen possibility, oxygen levels naturally drop overnight in ponds. No aeration in a pond can exascerbate this, as can the heat of summer. A fish kill overnight leads to the idea that either something caused the oxygen levels to drop (fish population/size hit a tipping point could be a cause), or affect the ph or biological filter.

 

[addy1]

Wow so sorry for your loss. Test the water to see where it is at.

 

[Mmathis]

Oh no!

How deep is the pond, does it have any type of water moment (fountain or filter with pump), is there any way that yard waste (or other chemicals) could have gotten into the pond?

 

[poconojoe]

That's terrible.

You need to test the water with a good test kit. The type with liquid reagents. The test strip type is known to be inaccurate.

Do you have any filtration?
Aeration? Or at least surface agitation that will help with oxygenation?

 

[miamicuse]

I am looking through @cas list and nothing jumped out.

It's an all naturally sustaning pond and been that way for many years. No filtration, no pump, no feeding, I don't do anything to it at all except when water level is low I top off with some water from the hose after adding a capful of conditioner. But I have not added water for the last three months, it's been raining fairly regularly in south Florida so the pond is not lacking water.

No tree cutting activities since May so saw dust from some toxic trees. No cutting of PT lumber or new PT lumber submerged into the water. The wood bridge that is 17' long and 36" wide is made of PT lumber but it's been there for I don't know how long may be 20+ years so I don't think it will contribute to this event. It's all rotted so I am actually getting ready to replace it.

I don't know if testing the water now will help because in a panic I saw so many dead fish floating on water but one still alive, whatever it was toxin or bacteria...I thought adding water will help not only it will dilute whatever may have caused this it will also bring the water to the highest level and bodies floating under the bridge will drift out. So I added some water conditioner and ran a hose shooting on a rock splashing into the pond, then I went to set up a net to scoop the fish out one by one. So after that I have already messed with the water chemistry in the pond at the time.

I am more leaning to some toxins. I know the lawn service was here on Thursday. They mowed my lawn, used the weedeater, they also may have sprayed stuff to control weed growth, but was told specifically to be careful around the fish pond...but I also know that they have had trouble finding and keeping employees because I see new faces every month so may be someone new wasn't aware, used the weedeater to cut off overgrown weeds, then sprayed some Roundup like products, then came back around last with the blower to blow some of this debris into the pond or into areas near the pond, then it rained heavily on Friday and the rain washed the chemicals into the pond? I did not check the pond on Friday morning before heading to work, I know they were fine and no sign of anything wrong on Thursday evening, and Friday late afternoon I came back to see everything went belly up.

I called the lawn service this morning and left a message to see if I can speak to the crew chief to find out if they used any chemical spraying on Thursday.

 

[Tula]

If I had to make a guess, I'd say low O2. I'm very sorry for your loss.

 

[SarahT]

I am looking through @cas list and nothing jumped out.

It's an all naturally sustaning pond and been that way for many years. No filtration, no pump, no feeding, I don't do anything to it at all except when water level is low I top off with some water from the hose after adding a capful of conditioner. But I have not added water for the last three months, it's been raining fairly regularly in south Florida so the pond is not lacking water.

No tree cutting activities since May so saw dust from some toxic trees. No cutting of PT lumber or new PT lumber submerged into the water. The wood bridge that is 17' long and 36" wide is made of PT lumber but it's been there for I don't know how long may be 20+ years so I don't think it will contribute to this event. It's all rotted so I am actually getting ready to replace it.

I don't know if testing the water now will help because in a panic I saw so many dead fish floating on water but one still alive, whatever it was toxin or bacteria...I thought adding water will help not only it will dilute whatever may have caused this it will also bring the water to the highest level and bodies floating under the bridge will drift out. So I added some water conditioner and ran a hose shooting on a rock splashing into the pond, then I went to set up a net to scoop the fish out one by one. So after that I have already messed with the water chemistry in the pond at the time.

I am more leaning to some toxins. I know the lawn service was here on Thursday. They mowed my lawn, used the weedeater, they also may have sprayed stuff to control weed growth, but was told specifically to be careful around the fish pond...but I also know that they have had trouble finding and keeping employees because I see new faces every month so may be someone new wasn't aware, used the weedeater to cut off overgrown weeds, then sprayed some Roundup like products, then came back around last with the blower to blow some of this debris into the pond or into areas near the pond, then it rained heavily on Friday and the rain washed the chemicals into the pond? I did not check the pond on Friday morning before heading to work, I know they were fine and no sign of anything wrong on Thursday evening, and Friday late afternoon I came back to see everything went belly up.

I called the lawn service this morning and left a message to see if I can speak to the crew chief to find out if they used any chemical spraying on Thursday.

I am so sorry to hear of your fish loss. Low oxygen is very common in the summers. Calling the lawn service is an excellent idea. You wouldn't want to add new fish to the pond of there are toxins in there. I hope you find the problem, or at least the fishy survivors continue to thrive and your pond returns to normal.

 

[Mgessert]

If the lawn service sprayed toxins around your pond, or in a way that allowed them to wash into your pond, then someone should lose their pesticide applicator’s license.

 

[Faebinder]

I am looking through @cas list and nothing jumped out.

It's an all naturally sustaning pond and been that way for many years. No filtration, no pump, no feeding, I don't do anything to it at all except when water level is low I top off with some water from the hose after adding a capful of conditioner. But I have not added water for the last three months, it's been raining fairly regularly in south Florida so the pond is not lacking water.

No tree cutting activities since May so saw dust from some toxic trees. No cutting of PT lumber or new PT lumber submerged into the water. The wood bridge that is 17' long and 36" wide is made of PT lumber but it's been there for I don't know how long may be 20+ years so I don't think it will contribute to this event. It's all rotted so I am actually getting ready to replace it.

I don't know if testing the water now will help because in a panic I saw so many dead fish floating on water but one still alive, whatever it was toxin or bacteria...I thought adding water will help not only it will dilute whatever may have caused this it will also bring the water to the highest level and bodies floating under the bridge will drift out. So I added some water conditioner and ran a hose shooting on a rock splashing into the pond, then I went to set up a net to scoop the fish out one by one. So after that I have already messed with the water chemistry in the pond at the time.

I am more leaning to some toxins. I know the lawn service was here on Thursday. They mowed my lawn, used the weedeater, they also may have sprayed stuff to control weed growth, but was told specifically to be careful around the fish pond...but I also know that they have had trouble finding and keeping employees because I see new faces every month so may be someone new wasn't aware, used the weedeater to cut off overgrown weeds, then sprayed some Roundup like products, then came back around last with the blower to blow some of this debris into the pond or into areas near the pond, then it rained heavily on Friday and the rain washed the chemicals into the pond? I did not check the pond on Friday morning before heading to work, I know they were fine and no sign of anything wrong on Thursday evening, and Friday late afternoon I came back to see everything went belly up.

I called the lawn service this morning and left a message to see if I can speak to the crew chief to find out if they used any chemical spraying on Thursday.

It must be the weed spray. that stuff flies everywhere even with the best attempts to contain it at times. I used to have this problem and lose several fish at the same time. A rain wash up would make it worse.

I used to go to do a 20% water change after each spray to reduce its effects...

 

[Lisak1]

Definitely poison when it’s everyone at once like that. I’m so sorry!

 

[jgrandmont]

Fish are very sensitive to chemicals. With such a high death toll, the Roundup seems to be the most likely culprit to me.

 

[Mgessert]

More likely to be insecticide rather than herbicide, to cause fish deaths. They should have given you a report of what was applied.

 

[GBBUDD]

I believe you said it was a natural pond?
looks like a concrete edging on one side?. The bottom has a lot of debris by the looks of it in a small pond, again from what i can see in the photo's.
I would strongly suspect lack of oxygen in the water i don't see an air stone or a stream nor a water fall. you had some good sized goldfish in there and with the high temps the entire country is dealing with i'd bet with certainty that is the problem here. let me guess the one goldfish that is still alive maybe one of the smallest as well?
it is possible some weed killer got in the pond but that more than likely would not have been a sudden death but more whats wrong with my fish episode.