Why are my fish dying this winter, but never before?

[3100Pond]

Pond is probably 9' long, 7' wide and about 2.75 - 3' deep.
Before the beginning of the winter I had probably 15 - 18 fish, some babies, and a couple that are more than a foot long. Don't know the combined weight of the fish.
Pond is probably 9' long, 7' wide and about 2.75 - 3' deep.
I drained the water down to about 9 or 10 inches and I now have not one, but two floating surface heaters to promote gas exchange. This has been my procedure for the past several years.
Now I'm really getting worried because I lost about five fish two weeks ago, when I found that one heater had quit on me, allowing the surface to completely freeze over. It wasn't frozen over for more than a couple of days, but not sure whether that might have killed the fish, I replaced it with two more.
This morning, I went out and found two more fish dead, floating on the top. And the surface hasn't even been iced over for probably a week! So I'm suspicious of a water quality problem, but, having disconnected my pump and filter, and having done nothing by way of filtration in previous winters, I'm not sure what the right solution is for winter filtration or even if that's the problem.

Any ideas would be welcome. Specific brands of equipment or whatever is recommended really appreciated since I know what I have used and had success with, but I certainly don't know all of the stuff that's out there.

Pls advise before I lose all my fish!

Thanks

 

[DrCase]

You could get a air pump for aeration for a start
Test your water and show the results

 

[3100Pond]

OK - can certainly get something to aerate, but it won't any good if it just freezes up when it does get really cold. Are there models that can tolerate some ice in the lines and/or are thermostatically controlled?
Second, about the idea of testing the water - that, I have to admit, is a bit of an Aha! moment. Never really thought about pH once I no longer had a way (filtration pump) to distribute any chemicals I might use to adjust the pH. I will test pH and post here (will feel REALLY stupid if pH is OBVIOUSLY bad). But either way, without a filtration pump, how do you evenly distribute chemicals to adjust? Just allow that aeration pump to do it? (that's if I can find one that will work in the really cold weather, followed by the not-so-cold weather).
Also, what other metrics besides pH? It's not like a pool, where I have chlorine and Total Alkalinity, presumably.....
And while we're on the subject of chemicals, do I use the same things I use to adjust pH in my pool during the summer, or something different? Have had to do very little to pH, even when the filter pump is running in the summer.
All thoughts appreciated.
Thanks!

 

[Waterbug]

Impossible of course to have any clue what killed your fish but here are some things you might what to consider and research.

This thing about keeping an ice free opening is something I've only read in the pond forums over the past couple of years. 5-15 years ago there was much less concern with a lack of gas exchange. IMO this has been a very one sided and not very well informed kind of a knee jerk reaction that ignores other dangers. So here are some points you may want to research further.

Lack of gas exchange is indeed a danger to fish. But the amount of danger should be considered too. As the fish load increases so does the danger, so a pond with a high fish load it might be important to keep an ice free pond (not just a small opening). But most backyard ponds don't have very high fish loads. I can't tell from your info what your fish load is.

The more organic waste a pond has the greater the need for gas exchange. If your pond is fairly clean and you did regular water changes last fall to reduce DOC levels an ice free pond becomes less needed.

No gas exchange is not an instant problem. The longer it's iced over the worst the gas problem becomes and the factors above dictate how long iced over conditions becomes a problem. In many cases 3 or 4 weeks of an iced over pond shouldn't be a problem.

The downside of keeping a pond ice free is lowering water temp. An iced over pond keeps the water very still which allows heavier warmer water to settle at the bottom. That's way easier on fish. Koi and Goldfish can survive 32-33F water but there is a time limit. If they have access to that warmer 39F water they can last a lot longer. Moving water can drop the water temp to a uniform value even below 32F due to minerals in the water, really low air temps even for short periods and small ponds.

Normally when I think of a gas exchange problem I think of a complete die off. Yes the less healthy will go first, but for gases to get that bad you're talking about all fish being at risk in a short time. Because you lost a few fish here and there I'd be more worried about cold water temps than gas exchange. It just stresses them a lot and that fits a more drawn out death rate imo. But of course it could be many other things too.

As for adjusting pH...most things that work don't really need any pump or movement, it's called diffusion. There are many things you can use to buffer pH including the swimming pool products. But whatever you use I suggest you have a basic understanding of what you're using. It's not super complicated but it's also not as easy as "my pH is low so I'm pouring something called pH Up into my pond". That's a really good way to kill fish. For example, ammonia isn't toxic at low temps and low pH. Raising pH without knowing your ammonia level is a good way to kill fish. You also have to understand what "Total Ammonia" is and how you can tell how much NH3 vs NH4 ammonia you have. If this is more than you want to learn about I suggest doing nothing instead. Nature is harsh, but in general can work through issues. But a human knowing a little bit and tossing stuff into the water can really be much worst.

Winter imo is a really bad time to be screwing with water. The fish are already on the edge of staying alive. In warmer water they can take more abuse, for example they can gulp air at the surface which they really can't do as well in very cold weather.

When you say you didn't have this problem last year, why this year? Lots of possible answers including the obvious one of different temps. Another possible is a build up of DOC levels. It can take a year or two for DOC levels to become problems.

Just my thoughts on the general subject.

I drained the water down to about 9 or 10 inches

I didn't understand this. I assume you don't mean what it says, that the fish are in 9 or 10 inches of water now. If you mean the water was 33-36" and was lowered 9-10" to 23-26" I don't think that's good. And while 36" should be fine it's also not great either although you're in a pretty moderate climate. The more shallow the water, the more water movement (heaters, wind, air pumps all move water) the greater the potential for super cooling the water which is very hard on fish.

 

[Dave 54]

Bicarb of soda is one way of adjusting your PH nother way is to make what is called a PH pill basically you'll need some plaster of Paris and a small bowl.
You put some plaster of paris into the bowl add only enough water to cause a reaction leave for 48 hours then when it is fully set take out of the bowl and place the pill into the pond where it will slowly disolve.
The good thing about the PH pill is you can make as many as you want to keep back for emergencies such as a lower than normal PH
Cleaning the pond before winter is a must and if using an aiirstone it should be kept of the bottom of the pond, just as a matter of interest what temperature is your pond at 2.75 - 3 foot is a little shallow for harsh winters unless the pond is heated.keeping a hole in the ice for a vital gas exchange, ideally you hould have a pond 4 - 5 ft in depth !!!... .
The same should be done with your filter cleaning it before winter too .
You can kick start it again with Microbe-Lift PL filter pad inocculant gel where you squease the gel onto your filter pads leave to soak ( in the Air for an hour then put it back into the filter) within a day or two you'll find your filter has all the good bacteria needed to start it off again , do the same to your filter again in the spring.
Rgrds
Dave

 

[addy1]

You drained your entire pond down to 10 inches of water depth? We had that really cold smack after very warm times, the temperature swings may be affecting your fish. With that little of water and your fish being larger than in the past few years, assuming the same fish in the pond. They may have fouled the water. If I am reading what you typed up there right.
My aerator kept my pond open, the water is deep. 5 feet or so, so far no fish loss.
Currently it is frozen over (electrical problem with the aerator line) around the edges the pond is open i.e. ice wise. Still no fish loss.

 

[sissy]

If you have a liner it will also harm the liner being exposed to cold and sun after awhile .Get a pond liquid test kit

 

[sissy]

I am guessing it may be a preformed and the plastic will freeze and crack after being exposed to extreme conditions .Hoping that your filter is not one of those pressurized ones because that could be a problem .They smell like a sewer after awhile and can poison the water .Do you have city water or well water .We have had a lot of rain in the last couple of weeks also and that can change water quality .Lack of oxygen may make it worse and hope you are not feeding them and if you are it should be wheat germ food .

 

[3100Pond]

Special thanks to Waterbug for his long and thoughtful post. Couple of questions to follow up on that, if I may...
You make several references to DOC - I probably know and understand the words that stands for (Biology major, so lots of sciences, including chemistry), but I don't know the acronym. Knowing what you're referring to may (or may not) preclude my having to ask about the "buildup" of "DOC" over the years.
Also, neglected to mention that my fish load is certainly much higher now than in past years - not my doing, just that, instead of the hawks and blue herons taking them, the storks apparently dropped some new ones off. So in that sense, I understand the concern that was expressed elsewhere, about the 9 or 10 inches of water that I left in the pond when I winterized it. The reason, however, that I started with that depth is that I had the lines to the external pump and filter blown out, because I didn't want to crack the pipes when the water in the froze. So now I have to be careful that the water from rain and snow over the winter doesn't raise the level back to the point where it can seep into the skimmer and fill the pipes. At present, I have about 2 - 2.5 feet of water in the pond, and I'm going to need to bail some of that out to keep the levels down until I re-open the pond and start the pump and filter.
So here's another question...while I'm at it, should I take 1/3 or 1/2 of that water out, while we're expecting some warmer weather, and replace at least part of it with fresh water?
Thanks again to all!

 

[addy1]

I leave water in my lines (external pump lines) leave the ends open, so far have never cracked, even with real cold snap we had. The skimmer, I stuff the basket/opening with bubble wrap, displaces the water = no ice.
DOC's
Dissolved organic carbon (DOC) is a broad classification for organic molecules
of varied origin and composition within aquatic systems. The
"dissolved" fraction of organic carbon is an operational classification.
Many researchers use the term "dissolved" for compounds below 0.45 micrometers, but 0.22 micrometers is also common, saving colloidal
for higher concentrations. A practical definition of dissolved
typically used in marine chemistry is all substances that pass through a
GF/F filter. The recommended measure technique is the HTCO technique after filtration on precombusted glass fiber filters, typically GF/F filters.[sup][1][/sup]

 

[3100Pond]

Dave54 in UK - also an appreciated post and a couple of follow-ups.
I like the pH pill - will try that. You inquired about pond temperature - I don't have a thermometer (that's also on the shopping list), but I can tell you that the water RARELY has more that 1/2" of ice on it.
And yes, I would love to have a deeper pond, but this is what I have. "Harsh winters"? Well, in this part of the US, not really, IMO....we get some stretches of below 25F for a few days but rarely an extended period like that, and they're interspersed with days of 40F and even 55F (predicted this Tuesday, I believe).
There've been several observations about the filter, so if I may add a bit of detail on that, I'll be glad for further thoughts....
I don't have a filter "pad" per se - this is a separate, external biological filter (you know, the ones with the little beads), with an oversized pump and supplemented, when the weather warms up, with a UV light to keep the algae under control. So given that setup, again, happy for any other advice.
Thanks!

 

[3100Pond]

Addy1 - thanks for your post on DOC. Understand the concepts well, just wasn't clear on the acronym. Appreciate the clarification.
So what, other than some water exchanges, leading up to the winter, do YOU do, to cut down on DOC buildup? My approach to opening the pond each year has been to as gently as possible, transfer the fish to the upper pond in my little waterfall/pond system, completely drain and pressure wash the lower pond (the larger one, where the fish spend all their time) and then refill with a combination of fresh water and the water from the upper pond, to minimize the fresh water shock to the fish.
I should think that getting rid of most of the water would be fairly effective, if the substances we're talking about are at least suspended, if not completely dissolved. But do you treat with any chemicals, beyond that?
Thanks

 

[addy1]

I am sure I have doc's, you have water, fish, plants, dirt you have docs, but my ppm meter reads the pond water as pretty darn clean. (If memory serves me right..last fall the pond read around 200 ppm, my house fish tank reads around 200 ppm. The fish tank gets its water cleaned and changed a whole lot more than the pond. Never have the white foaming stuff on the surface of the water which is a good indication of excess DOC's My pond is filtered with just a large bog (pea gravel and plants)
I would need to take current readings to see what it is after sitting all winter.
I never drain or clean the pond like you do. When you pressure wash it, you are removing the good carpet algae and basically starting out every spring as a new pond. imho
Leading up to winter, I net any junk off the bottom i.e. falling leaves, old lily leaves etc. Leave a bunch of stuff for the tad poles, snails, fish to eat over winter.
No water changes.
In the spring, no water changes, unless it rains hard (gutters feed into the pond) All I do is bring the pump out of the basement, put it back in line, turn it on. That is the extent of my start up. No chemicals ever. I do add crushed oyster shells to bring up the hardness of my pond water. Our well water is very soft and acidic. To keep the ph decent I try to keep the hardness up.

 

[Dave 54]

Deapending on the depth of a pond it is possible to use the trickle meathod of doing waterchanges throughout the winter here in the UK ( not sure about the US in your colder zones ) but it requires a bottom drain in your pond leading to the filters
By trickling the water through a hose at a very slow rate it allows the ambeant temperature of the pond to acctually take out the cold without loosing temperature.
For example our pond is 4ft in depth with a bottom drain into its filtration system , this allows me to take out water from the bottom of the pond on a weekly basis at roughly 30%.
I then over a number of hours trickle the missing 30% back into the pond loosing approximately .1c - ,2c in total.
So say I did my waterchange tomorrow with my pond as it is at 12.7c , I would end up with a temperature of 12.6 -12.5c
It's a case of if you are thinking of renewing your pond look into a larger filtration unit supplied by a 4" bottom drain I'm affraid but koi keepers have been using this method for quite a while now our pond is heated via its insulated filter housing via a small oil heated radiator on its lowest setting to a pond with polycarbonate sheeting covering it .
rgrds
Dave

 

[Waterbug]

You make several references to DOC - I probably know and understand the words that stands for (Biology major, so lots of sciences, including chemistry), but I don't know the acronym. Knowing what you're referring to may (or may not) preclude my having to ask about the "buildup" of "DOC" over the years.

Unfortunately the acronym is used for several things, dissolved organic compounds, dissolved organic carbon, decomposed organic compounds and I think I've seen others. When used in the context of ponds it virtually always means any suspended organic matter. That can range from the smallest dissolved organic carbon to what can be larger dissolved organic compounds that Aquarists often refer to, up to the largest bits that can be called decomposed organic compounds that you can see suspended in the water. So in pond forums I think DOC isn't actually an acronym at all because it's used to cover everything. In my post DOC was referring to suspended organics being subject to aerobic decomposition which consumes O2 and therefore a problem for iced over ponds.

Things like dead algae, leaves, sticks, even fish poo decompose on the pond bottom (or inside filters) and can take months, even years, to decompose completely into small enough bits to become suspended. So generally the older the pond the greater the potential for high DOC levels.

about the 9 or 10 inches of water that I left in the pond when I winterized it. The reason, however, that I started with that depth is that I had the lines to the external pump and filter blown out, because I didn't want to crack the pipes when the water in the froze. So now I have to be careful that the water from rain and snow over the winter doesn't raise the level back to the point where it can seep into the skimmer and fill the pipes.

I see, you dropped the water level to keep it below the skimmer.

I've mentioned this a couple of times over the years, but it's kind of a waste of time because pretty much no one believes this (some myths are stronger than others) but I'll roll it out again because I find it interesting. While there is always a chance of damage from expanding ice the risk is much, much smaller than most people believe. Here's a good explanation imo. Most plumbing in a pond is open at both ends so the danger of pipes bursting is almost zero. I think the highest risk would be inside a UV and maybe some filters, but even then it's a pretty low risk. Winter is hard on plastic and it can crack. Most of the time this is blamed on ice but most of the time it's just low temps. I know the fear of ice is pretty overwhelming but it can be understood better.

At present, I have about 2 - 2.5 feet of water in the pond, and I'm going to need to bail some of that out to keep the levels down until I re-open the pond and start the pump and filter.

I don't know your exact climate, but that's not a lot of water. The heaters might be needed more just to keep any water. At least in NY 2.5' would freeze completely. But I do know there are a lot of 2' deep ponds in cold climates. Aquascape (biggest pond builder) says:

There are thousands of two-foot deep ponds around the country, full of happy and healthy koi. The water in a two-foot deep pond will generally only freeze eight inches down, even in the coldest of climates, because of the insulating qualities of the earth that surrounds the pond.

I assume it's true because in Aquascape forums and from I've heard from Aquascape dealers I've never heard of unusual die offs. But holy cow really getting near the absolute limits of what fish can take.

BTW, by far I think there are more Aquascape ponds than any other kind of pond and almost none use any kind of device to keep openings in ice and they're also not lowered below the skimmer. These ponds have pretty normal type problems, meaning no more so than ponds with heaters, etc. When you read in pond forums you're hearing from a very small segment of the hobby who can get a kind of unique and insular understanding of ponds. If you expand to consider all ponds you can get a much different understanding.

So here's another question...while I'm at it, should I take 1/3 or 1/2 of that water out, while we're expecting some warmer weather, and replace at least part of it with fresh water?

I don't like to screw with water in winter. I like to test water first so I kind of understand where I'm at before I change stuff. I don't like to "fix" something unless I have a pretty good guess that it needs fixing. Just because I mentioned DOCs doesn't mean you have a DOC problem. Good way to kill fish is to fix something that isn't broken. But I don't see any great harm as long as you understand how to properly.