Mysterious deaths

[bagsmom]

A while back, maybe around Thanksgiving or so (I can't remember - it may have been early December) I checked my skimmer, only to find a VERY dead fish. Part of him was just skeleton. The matala pad under the skimmer basket was filled with green scum and tiny white worms. I was assuming it was all part of the cycle of decomposition and that may still be the case. Since then, I have had 3 more fish die - the deaths have been weeks apart. The fish all look fine, although thin, and before dying, start hanging out alone near the bottom. All the other fish have been behaving normally. I am now down to 11 small fish in the pond, which is somewhere around 1200 gallons, I believe. It is definitely NOT overstocked. I run the pump 24/7 and have since I built the pond 3 years ago. There are lots of plants. The net has been on since early September.
I haven't fed them since the weather turned cold initially. I have an ecosystem pond with tons of plants, so I seldom feed them even in warm weather. I know the filtration is all flowing well and the waterfall keeps everything aerated. We have had some humdinger heavy rains and back and forth temperatures. But that is typical for the south. The fish appear to be healthy - no outward signs of any diseases.
I haven't done a water test. I know I need to. It has just been so chilly, I don't want to put my hands in the water!
Does this sound like anything anyone is familiar with?

 

[bagsmom]

Here is a photo of the pond, just to give you an idea of the set-up.

 

[brokensword]

Here is a photo of the pond, just to give you an idea of the set-up.
View attachment 146125

of course, you're going to hear 'test the water', as ya got to be sure it ain't that. Thin isn't normal. And if you're not watching regularly, hard to see patterns that indicate problems currently in play. Could just be old age. Could be a disease/illness/bug, but that's why you need regular watching. For me, this kind of think happens only during the early spring, coming out of winter and not that much. Last year was worst at 5 gf and 2 koi, though both koi had never overwintered. And I had flashing that eventually cleared up. Soooo, really hard to say without some other clues, for me at least. Hope this isn't an ongoing issue for you.

 

[bagsmom]

Me too! Thanks! I do wonder if it is something to do with the strange and changeable weather. No one is flashing. No weird growths or dots or bumps or fuzz. It is very odd. I will force myself to get out and do a test tomorrow.

 

[Mmathis]

Yes, testing the water is a good step. We have been having weird weather (even here in LA). If it was only one or maybe even just 2 fish, my answer might be “sometimes fish just die,” but this is suspicious. Is it possible that something died in the pond, like a squirrel or something? I found a dead squirrel once, but I think I got him out of the water before decomp started (it was in winter).

Your pond is beautiful, BTW!

 

[j.w]

What are the symptoms of acid rain I wonder? How would fish act? Since you said you had been getting a lot of it. Maybe check the levels.

 

[WaterGardener]

Rain on the East coast is generally acidic. It can use up the alkalinity in the system and cause a pH crash, killing the beneficial bacteria and the fish.

Water tests are necessary to know if the water is safe or not. No need to get your hands in the cold water. Just use a cup or anything else that will hold water and scoop some up. Take that inside and fill the test tubes with a syringe and add the regents for each test. No muss, no fuss and no cold water on your skin.

 

[bagsmom]

Whether coincidental or not, I think it is interesting that the fish seem to be dying in order of size. I know low oxygen levels kill off bigger fish first, but I can't imagine this would be the problem. My waterfall has a very robust flow and the water movement is good between the waterfall and skimmer.

 

[SarahT]

Is it possible the heavy rains washed in runoff water from uphill, maybe an area treated with chemicals of some kind, like weednfeed or fertilizer or pest control? Is the water cloudy at all (I'm wondering about house painter cleaning brushes, even far away on the ground)?

 

[bagsmom]

Is it possible the heavy rains washed in runoff water from uphill, maybe an area treated with chemicals of some kind, like weednfeed or fertilizer or pest control? Is the water cloudy at all (I'm wondering about house painter cleaning brushes, even far away on the ground)?

Thankfully it isn't that. I was super careful with my pond construction to ensure that could never happen. I'm going to take my test kit out today and see what I can find out!

 

[bagsmom]

I went outside and took the net off the pond today. I lowered the water level a bit and looked around to see if there was anything gross or dead in there. Nothing that I could find! (Whew!) I got out my water test and found that a couple of the test chemicals had expired. Ph was useless because it was one of the expired ones. I got three wildly different results with three different tests. I will have to get more chemical for that. Ammonia and nitrite were two that were still current. Zero on both! I'm still wondering if the fish deaths had to do with the giant rains we've been having - changing the pH too rapidly. I will have to check the water again when I get new chemicals. For now, I cleaned the matala pad under the skimmer and just observed a while. The remaining fish all seem good - very busy in spite of the cold water!
The only thing I noticed that was different this year was the pothos plant that rooted in the waterfall basin. I think it is safe for aquatic life but I know it can be harmful to mammals. Just to be safe, I pulled it out. Here are some more pictures after removing the net.

 

[WaterGardener]

Good to know your ammonia and nitrate are okay. PH would be nice to know when you get a new test.

Please also get a KH test. To me that is one of the most important things to test for.

 

[bagsmom]

Good to know your ammonia and nitrate are okay. PH would be nice to know when you get a new test.

Please also get a KH test. To me that is one of the most important things to test for.

Would that be an issue with rainwater? I always think of hard water as coming from the tap.

 

[WaterGardener]

Rain tends to be acidic, so it will overwhelm the alkalinity in the system and cause the pH to drop into the acidic range, a pH crash. This cam kill your beneficial bacteria and your fish.

KH is the measure of alkalinity. If you have plenty in the water, it will prevent that crash.

Depending on where you live, tap water can be acidic, alkaline or even neutral.

 

[brokensword]

Would that be an issue with rainwater? I always think of hard water as coming from the tap.

what WG said; a KH kit will let you know if your pond water can HANDLE pH changes. The acidic rain water would be negated by the mineral in your water to absorb it, if KH is properly high enough. This stops the pH crash you're alluding might have happened.