Goldfish dying

[JohnY]

I have a relatively small pond 5'x8'x1.5' - waterfall, 2000gph, pressurized biofilter, 18W UV clarifier, air pump for the past 10 yrs. My original 5 goldfish have spawned multiple times and I had approx 20-30 fish at all times. Recently my fish have started dying at the rate of 1-2 per day so now there are about 4 left. Water chemisty is NO2, NO3, NH3 at 0, pH at 7.6. I had kept the salt conc at 0.05-0.1% throughout. The latest heat wave did not help however the fish started dying prior to the weather. Not sure what to do, please advise.

TX

 

[MitchM]

Welcome.
Can you post a picture of your pond?
Have you examined the gills and body of the dead fish for any unusual colours?
Could there have been any pesticides or herbicides get into the pond?
Just to be safe, it wouldn't hurt to get some activated carbon in your system in case something toxic did enter the pond water.
What is the water temperature?
What have you been using for water testing? 0 NO3 seems low.

 

[JohnY]

Attached is a picture of my pond, in the foreground you can see the output of one of the airstones, in the background is the waterfall, note the amount of plant roots in the water I imagine this reduces the Nitrogen. I've used a freshwater master test kit which gives colormetric results in each case the levels were less than the lowest amount. I haven't used any chemicals near my pond not sure if my neighbor did though, I do have a supplemental pressure vessel filter with activated carbon in-line with my normal filtration. The dead fish all show no obvious signs of trauma the gills were pale red but I am not sure how long they were dead (<24hrs) I would have thought that with the waterfall and air pump I have a saturated oxygen environment.

 

[MitchM]

How often do you change the carbon?
Have you ever tested for GH/KH?
What is your pond maintenance routine? Do you perform regular water changes or vacuum the bottom?
Where are you located?
When did you first notice the fish dying?
Do you have any submerged plants?(I'm guessing not with the salt level)

 

[Usman]

did you notice any thing unusual in their behaviour , movement , appearance or eating breathing habits . you have lost so many fish ... do you have hospital tank? i would recommend observing and treating fish in an aquarium , if they look sick give them medicated food and any general purpose med ,do water change 30% of pond and cleaning .

 

[JohnY]

1. I change the carbon usually once a month
2. Never tested hardness, did not seem warranted prior to this episode
3. Sacramento, CA just finished a string of 8 days over 100 degrees, however this is not unusual for summer and did not adversely affect my pond in the prior years.
4. About 3 weeks ago, now down to four fish. Perhaps best to drain, clean and start over however still perplexed over what happened everything was great the previous years.
5. No plants underwater
6. Appearance was normal as far as I could tell, initially had too many fish to isolate once the "outbreak" started I guess now with only 4 fish left I could put them in an aquarium and start over but again still a shame since things were going well.

 

[MitchM]

Maintenance routine?
Starting over may sound good, but without identifying a potential cause, I'm not sure what that would accomplish.
I asked about GH/KH in case there were a series of PH crashes occurring.
Have you ever tested your source water? Any potential concerns there?

 

[Meyer Jordan]

Are you on Sacramento water supply or another supplier?

 

[JohnY]

I agree about finding the root cause so as to not repeat the situation. I have been using West Sacramento city water as my source, currently I have a small leak in my liner causing me to introduce about 125 ml/min of city water into the waterfall. My back of napkin calculation show this creates a complete turnover of the water in 8 days, I have doing this for again about 8 years now so nothing different in that regard if fact I thought it might be good in removing harmful buildups (Ha!). My maintenance is sometimes spotty with a filter change out every 3-4 weeks, considering I have over engineered many of the components for the small pond size. Is it possible some plant material may be toxic after falling into the pond and decomposing?

 

[MitchM]

My back of the napkin calculation tells me that you are adding about 50 gallons per day to your pond, about half that amount should be from evaporation for your size pond in your area.
Perhaps Meyer Jordan has some specific information regarding the Sacramento water supply.
My first thought is that you may be seeing a buildup of either toxins or minerals that you haven't tested for.

 

[Meyer Jordan]

I would certainly test for GH as well a KH, as @MitchM suggested.
According to the West Sacramento Public Works the GH of the water has steadily declined over the past Three (3) years:

2014 - 64 ppm
2015 - 52 ppm
2016 - 45.5 ppm

Water that is too soft has been known to cause issues.

 

[JohnY]

What is the optimum hardness level(s) I should be looking for and would this cause the massive die-off?

 

[Meyer Jordan]

What is the optimum hardness level(s) I should be looking for and would this cause the massive die-off?

A minimum level of 30 is recommended for most ponds. 60 - 100 is a good level range for most any pond, although some will recommend levels higher, it really offers no proven advantage. Ideally GH and KH should be the same level.
If your water is indeed soft (below 60, only testing will tell for sure), although it may not have directly caused the fish deaths, it is possible that it may have contributed.
As water hardness rises, heavy metals and some other chemicals become less toxic. Hardness typically adds Calcium and Magnesium to the water, both essential elements in the health of all aquatic life forms. Hardness also bolsters Alkalinity which in turn buffers the pH, preventing any wide swings.

 

[JohnY]

Mitch & Meyer, thanks for your help.

signing off, JY

 

[MitchM]

You're welcome, but I don't think we've identified a probable issue.
Let us know if we can be of further help.