Why did I have a die-off in my pond?!

[researcher]

Hi; I'm new to the forum -- after having a backyard pond for over 10 years!

Never had a real issue with the pond (other than visits by a blue heron, but since I only have goldfish, no big deal) ... until lately.

My pond's maybe 1200 gallons. I generally keep a fish pop of ~25-30; that seems to be the carrying capacity. No aeration -- I use elodea for oxygen generation, and the pond always seems to have a good equilibrium. Lots of plants (subsurface and on the surface).

As a rule I let maybe 50-60% of the surface get covered with water hyacinth and water lettuce (to keep algae #s down). This summer, though, I let the plants cover about 90%. Oddly, I sometimes saw a film-like "something" form on the exposed areas. No problems with the fish that I could tell. No struggling for air, or deaths.

A month ago, though: I began to pull out the XS vegetation. Noticed later that several fish per day were dying! Took out 4 remaining fish (saw no others alive), changed water (letting the city water set for a day -- to kill some negative organisms, I hoped), treated the water, then put the 4 fish back. A day later -- another dead fish. Haven't see the other 3. Also: I've seen no adult frogs; another milestone. Found several dead ones in the pond. A # of tadpoles were around, at least.

So .... any ideas/anecdotes/possible explanations? I've wondered if there was a disease issue. In a "test" at PetSmart, I was told the water was "acidic" [no # given] but that ammonia level was OK.
I fed the fish until cold weather began, and they lost interest in the food, so I don't believe starvation was the problem.

For what it's worth: in June or so, I added about 6 fish from an alien pond; could they have spread some disease?

Sorry for the long epic, but to get a comprehensive answer, I had to use all the data I could .....

Mitch

 

[addy1]

Welcome to our forum!

These are maybe's 1) your population was too large when you pulled excess plants the ability to control ammonia went away
2) there was a o2 level issue.
3) the added fish back in June, most likely did not harm them this much later.
4) how acidic? My well water is around 5.3 I had to buffer it up to keep fish, ow they just died.

 

[researcher]

Thx, Addy; I guess for clarification, I should add --
1. per the little test I had done, ammonia was fine.
2.the fish seemed to do OK with the oxygen (none ever coming to the surface for breath)
3. the PetSmart test only indicated "acidic", no actual datum. Could've been 6.8 (fine) or 3.0 (fatal). No idea.

 

[Mmathis]

Hello and welcome!

I agree with what @addy1 said. There are a lot of reasons for a fish die-off, but it’s often a combination of events — especially if you make several changes at a time.

My advice is to buy your own water test kit. Don’t rely on a pet store to test your water. Water quality is the number one cause of problems. Most of us use the API Master kit. Add to that the kit that includes KH and GH. Keep in mind that water chemistry is a balancing act — each value can effect the other values if they get out of whack. BTW, these are liquid, drop test kits. They are more accurate and more dependable than test strips. Get back to us with your results.

 

[mrsclem]

Hello and welcome! Sorry for you loss of fish. Acidic water could well be at least a part of the problem but also adding fish from another pond. New fish need to be quarantined ( we all know about that this year!) Get the rest kit, let us know the results,especially the ph.

 

[sissy]

plants use up lots of oxygen at night .The more plants the less oxygen they have at night to survive

 

[Tula]

Welcome I agree with others, buy your own API Master kit and test your pond water.

 

[j.w]

@researcher
Yep I agree get yourself a test kit. Do you have a pump in your pond filtering the water?
Plenty of aeration is good too. I use mine only in the Summer tho but I leave my submersible pump and waterfall running all year long.

 

[sissy]

I used to leave one pump running in my waterfall but after the year the ice diverted the water and I could not tell it until I noticed the ice was sinking al around where the pond heater was and there i was in a snowstorm with a house run from the basement into the pond because I only had about a foot of water in the pond and hoping that the well water was not to much different in temperature .I was also worried about the power going out before I got enough water in there to save the fish .I had a hard time getting the power cord free from the ice so I could lower it down to where the water level was at .I was lucky I got almost 3 feet of water in the pond before daylight .I had to keep turning the water off so I would not over heat my well pump so it would not burn out since it is over 400 feet in the ground

 

[researcher]

Much obliged for all the thoughtful input. I'll be on the prowl for a test kit now.

I don't use aeration; when I began the pond years ago, I wanted to see if the elodea made enough O2 for the fish [the pond's in direct sunlight maybe 6 hrs/day and dappled light maybe 3+ hrs during summer] . Apparently did, since I never had any issues. 'Til now.

Let's hope for a worthwhile 2021. I won't say, "It's gotta be better than 2020!", like I hear some folks say -- we all know why ....

Mitch

PS: something nobody mentioned -- my adult frogs all disappeared. I've never seen that happen. Tadpoles left, but that's it. Also, the # of mosquitofish seems to've plunged. I didn't think anything or anybody could kill them.

 

[TheFishGuy]

Much obliged for all the thoughtful input. I'll be on the prowl for a test kit now.

I don't use aeration; when I began the pond years ago, I wanted to see if the elodea made enough O2 for the fish [the pond's in direct sunlight maybe 6 hrs/day and dappled light maybe 3+ hrs during summer] . Apparently did, since I never had any issues. 'Til now.

Let's hope for a worthwhile 2021. I won't say, "It's gotta be better than 2020!", like I hear some folks say -- we all know why ....

Mitch

PS: something nobody mentioned -- my adult frogs all disappeared. I've never seen that happen. Tadpoles left, but that's it. Also, the # of mosquitofish seems to've plunged. I didn't think anything or anybody could kill them.

have you thought about something such as run off? there may be chemicals from yard fertilizer, pesticides ect.

Personally I would get an icp lab test, it will basically tell you if anything is off as far as chemical composition goes ( however they are a bit excessive and expensive )

 

[researcher]

I've wondered -- but I don't use pesticides in my yards, and little fertilizer.
Here's a little something, though: stoopid 'coons play and wash in the pond (!) and sometimes they "disgrace" themselves right on the stones surrounding the pond. Maybe in the pond?! I've wondered if something even like that could make an impact -- disease, possibly? Odds are I'm gasping at a straw, but ....?

By the way: any ideas re: where to get a reliable/good pond-testing kit? I like to avoid online anything when possible; shipping costs, etc. I've never checked with any pond-related business or Lowe's about it.

Thx much ....

Mitch

 

[Mmathis]

I have been getting my latest test kits from Amazon, and shipping hasn’t really ever been an issue. Most pets stores carry them (avoid test strips). Look for the API brand, Freshwater Master kit. You’ll have to get KH & GH as separate add-ons — they aren’t included in the Master kit.

You can check places like Lowe’s, but I would think they would carry pool testing supplies, rather than pond testing supplies. What you want, tests for: pH, ammonia, nitrites, nitrates, KH, GH.

 

[Lisak1]

Welcome @researcher . Sorry to hear that it's pond troubles that brought you to the GPF, but hope you'll stick around.

You mentioned raccoons using your pond as a toilet. Raccoons do carry roundworms, which can infect fish. Let me share what happened to our pond one spring. We were thrilled to see a pair of nesting mallards on our pond one morning - how cool! They hung around for several weeks, building their nest in some bushes in the yard and swimming in the pond throughout the day. They didn't appear to be bothering the fish so we just enjoyed them.

Then the fish started dying. Two the first day, four the next, a few each day... it was a slow but steady process, but clearly we were going to lose them all. We tested the water - no clues there. The dead fish showed no signs of infection or illness - no redness, no bloating, nothing. (We've never scraped and scoped a fish - probably something someone with more experience would have done.)The few that we observed in the process of dying happened within hours - appeared healthy, eating, swimming, etc and then started hanging near the surface. Not gasping or struggling in anyway... just appeared almost lethargic. Within hours the fish would be dead. We have a negative edge pond and the fish would just appear too weak to swim and float right over the edge into the rain exchange. We rescued a few that were still alive when we found them, but they rapidly died.

We consulted with a local fish dealer and he suggested we use praziquantel on the off chance that it was some kind of parasite that was being passed from fish to fish. We hadn't added new fish - which is often the source - but then we remembered the ducks. Water fowl are known to carry parasites that don't affect them, but can be deadly to fish. We got the Prazi, administered the appropriate dose and the die-off stopped almost immediately. We lost two more that were probably already too far gone, but that was it.

We had people (pet stores, pond stores, other pond owners... we called everyone!) suggest that the pond had been poisoned in some way by run off or overspray from pesticides, but we don't use any in our yard, so that seemed unlikely. But the fish guy we consulted said he didn't think that was a concern because they fish would have died all at once, not in a slow process. Ours were clearly being affected one by one by something. I just checked my notes that I kept from that event and in all we lost fish over the course of nine days - a total of 22 fish died before we landed on Prazi as a potential solution.

Was it actually the ducks? We won't ever know for sure, but when they came back this spring, we aggressively suggested they find a new nesting spot!

 

[researcher]

Much obliged, Lisa; news to me re: the vectors. Since it's winter, the water has been changed, and no life can be seen in the pond at present (the 3 fish and any surviving frogs may be hanging at the bottom -- or dead), I guess I have time to wait-and-see, or experiment. Test kit 1st, then maybe a treatment of some sort.

Happy new year! So far, it's been 1 of my best -- 5.23 days into it ....

Mitch

PS: I'm wondering -- if everything's dead in the pond, would time eliminate any disease-carrying protozoans or vermin? I mean, if they don't have hosts, then ..... ?