Pond Fish

Below you’ll find an email that I recently received from our friend and customer, Hilde B.

Hilde, had asked me to share this information with you as we get into fall as a reminder to folks that there are a few things you can do to help your fish over winter safely. Unfortunately this winter, Hilde lost all of her fish.

I decided instead to post this now, just in case, since many of our friends from up north are still in cold weather. I’ll repost this again in the fall as Hilde suggested as well.

I particularly found her statement, “It’s a matter of what you don’t know that will hurt you”. How true this is. If you have a pond, you must continue to learn, study, and apply things that will make it a cleaner, healthier, and balanced place for fish and wildlife. I’m convinced we’ll be amply rewarded for our persistence.

And we can continue to learn because people like Hilde are willing to share their experiences…both good, and not so good.

Thank you for that Hilde!

Hello Mark,

There was a time when all I could think about was, clear water. We ran into a very different problem, all fish dead. Was sad to see this a couple of weeks ago. It’s a matter of what you don’t know that will hurt you.

We have had our fish pond for only 3 yrs. It came with the house when we moved to Ansonia, CT. The fish did fine the past 2 winters. This time, we have had a very severe winter. Ice on the pond for too long. I’m pretty sure that this was the problem, hypoxia, the fish ran out of oxygen. Most likely, a pond heater/de-icer would have kept them alive.

Very distressing thing when your fish die and you could most likely have prevented it. I was very fond of them, had even manged to train most of them to be hand fed (they loved honey nut cheerios). You could do a real service by mentioning pond heaters/de-icers when fall rolls around again. Not very expensive either, worth investing in, just in case…

With my regards,

Hilde

It’s nearly a consensus among pond experts.

When they are asked to evaluate a backyard pond with algae problems, more often than not they track the root of the problem back to fish in the pond. Fish may not be the primary cause in every case of pond algae, but their influence on the pond is always something to consider.

Now keep in mind, what I’m talking about here in general is the smaller backyard pond. Any small pond is like the proverbial fish bowl. They only hold so much water, and they’ll safely hold only so many fish.

In the simplest terms, fish eat, they digest what they can, and then they produce waste. And like any waste material, their donation makes good “fertilizer” for plants. It’s really part of the natural balance of things when you look at it. Good, desirable plants, live off waste material of fish and as they do, they clean the pond, and balance nutrient levels out too. This keeps ammonia levels, among other things, in a reasonable range which is a great aid to the fish.

There’s only one problem with all of this. Algae is a plant too. And it loves fish waste, decayed food, or organic matter of any kind that’s breaking down into an algae edible form.

It may seem strange to think of algae as a pond balancer, but that’s exactly what it is. It is working to clean up some imbalance (most often nutrient based) in the water. For all of it’s good deeds, this doesn’t mean we have to like it any more than we do, but it might help keep the whole battle with algae in perspective.

Getting back to the fish though.

If you have too many fish in a pond for it’s overall size, then often no matter what you do, it will be hard to keep algae totally at bay. You end up fighting a losing battle because it’s very likely that your filtration system might be overwhelmed, and other desired plants, while helpful, may just not be able to do enough.

So here’s a rule of thumb when it comes to fish in a small pond. Be sure to allocate 10 gallons of water for every inch of fish (and this includes all fish except Koi). For Koi you’ll want to allocate about 25 gallons of water for each inch of fish.

This means that if you have a 1500 gallon pond, this can support up to about 60 inches of Koi. Anything over this amount, and they could be adding significantly to an existing algae problem.

Be sure to try to stay under this ratio to ensure a healthy fish population for your pond size. By doing this, adding desired plants, supplementing with beneficial bacteria, and making sure your filtration systems are operating well, you’ll likely stay ahead of most algae problems before they develop.

One final note on fish. Be sure to not feed them too much food. If you find that a good amount of food is going uneaten and sinking to the bottom, slow down in amount or frequency. One rule of thumb is feed them no more than they can consume in about five minutes time, once per day. This will minimize uneaten food from building up and decaying at the bottom of the pond

It’s hot, it’s steamy, and no, it’s not a romance novel. It’s the summer weather in most of the country as we move into June and July. This is a perfect time to talk about a phenomenon that often occurs during this time of year and it’s not a pleasant development if you have fish.

The incident is called “inversion” and it’s one of the various things that can deplete a pond of oxygen…quickly. Inversion usually won’t occur in smaller ponds, however larger ponds with a fair depth of 10 feet or more may be susceptible.

As the weather warms up a pond can experience the development of layers that vary in temperature and oxygen density. The upper level of the pond will develop rapid warming which creates water with lower density. Along with this reduction in density, the water will have a decreased ability to hold oxygen. Simply put, warm water holds less oxygen than cool water.

Usually though, with the help of photosynthesis and oxygen exchange there is enough oxygen to sustain fish populations.

As you go lower in the pond, the water begins to cool and while cooler water will hold more oxygen normally, due to the lack of photosynthesis and decaying organic material at the bottom of the pond, you’ll actually find less dissolved oxygen in the lower layers of a pond compared to the surface or top layers.

When environmental factors get rolling like really strong winds, or extremely heavy rains, then an inversion can take place. This represents a complete turnover or flipping of the pond from top to bottom. In other words the cooler, lower layer goes to the top and the warmer upper layer goes to the bottom.

Fish tend to like to stay near the surface or mid-layers where more oxygen is present in normal conditions but when changes can happen so quickly, they can experience oxygen depletion and suffocation.

Visually you may notice that the pond becomes almost black or very dark, where there was once relatively clear water. It may smell badly since the decaying matter has now been displaced and moved towards the top of the pond.

Often what’s most surprising to pond owners is how quickly this can take place and it can take some time for the pond to return to a normal state or condition. Nevertheless, in a matter of minutes the damage can be done to fish populations and certain sensitive species such as trout can be affected with even moderate oxygen depletion.

So how can you guard against inversion in your pond?

While there are no absolute guarantees of protection, one of the very best additions you can place in your pond is submerged aeration. We talk about this quite a bit but it can’t be stressed enough. Aeration adds consistent and reliable oxygen levels in a pond and it does so in the lower levels where oxygen content is inherently low. This simple act can provide a level of insurance against complete oxygen depletion in a pond and it also improves many other factors in the overall health of a pond environment.

Secondly, one of the elements that adds to the negative affects of inversion is heavy organic build up at the bottom of the pond. This gunk is literally like rotten compost, and this is often the material that turns pond water so black and disgusting when a pond turns over. So, reducing this element in a pond is a good thing to do.

For large ponds there are really only a few options that you have to reduce this organic buildup. Dredging or the manual scraping and cleaning of the pond bottom or the through the ongoing use of beneficial bacteria.

Bacteria plays an important role in controlling algae growth but one of it’s other great qualities is the enzyme activity that helps maintain the natural breakdown of organic solids in a pond. Studies show that proper bacterial applications with adequate oxygen can “eat away” or reduce bottom organic sludge by up to 3 to 4 inches in a season. By our definition a season would include spring, summer and fall. In wintertime most bacteria and algae become dormant.

So the moral of this story is that if you have a larger pond with adequate depth and you have fish, be on the lookout for the early elements and conditions that can lead to pond inversion. Do your best to keep adequate oxygen levels in your pond and work to keep the bottom free of excessive organic build up. By doing these two things, you may very well be able to avoid an inversion in your pond even when mother nature throws a variety of conditions your way.

Well it was quite a response.

Of all the articles we’ve done so far, the one about keeping pond fish safe from predators really generated a lot of responses from our readers.

This doesn’t surprise me really. Pond owners are helpful, caring people, and many know what it’s like to find a heron, raccoon, cat, or other critter looking for fish for dinner. I guess that’s why I’ve never seen so many suggestions or tips come in via email regarding how to keep them all at bay.

Suggestions included motion activated lights, decoys, guard dogs, border wires, netting, and more. In my book, nearly anything goes as long as it’s legal and doesn’t harm anything.

So in the spirit of trying to help other pond owners from this plague, if you have a tip or technique for dealing with predator problems around your pond, please share it here. You can do so by using the comment section below. That way everyone can learn as we go along.

We all appreciate it!