Protecting your koi from predators

Don't feed the herons!

As you might imagine, there are a handful of animals here in South Jersey that given the chance would instinctually treat your koi pond as their private food stash.  This is not too surprising considering this is a fish whose beginnings were as a humble food fish, farmed by people in Eastern Asia.  As far as we know, the modern ornamental koi has only been around for one or two thousand years, barely a blip on the grand scale of evolution.  Its existence here in the pinebarrens is a recent development, brought about by the fascination with Japanese koi ponds in the minds of American soldiers returning from WWII.  Even the koi's ancestor, the common carp, has only been in the waters of NJ since the mid to late 1800's.  This means that the wild animals in our backyards have not evolved alongside these fish, something that is both a blessing and a curse for koi-keepers.  On the positive side, not having lived among carp/koi means the predators are not accustomed to considering them as a food source; when they get hungry there is no instinct telling them to fill their belies with carp.  On the negative side, it means that when one of those animals discovers a novel and untapped food source in your pond, it will likely exploit it for all its worth.  

Click 'Read more' down on the right to learn how to keep your koi safe...

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When koi are released and are allowed to breed in the wild, they do not retain their brilliant colors.  These fish will soon revert to a dull shade of mud-yellow without any human intervention.  By the fourth generation, wild-born koi will have nearly all of their colorful ornamentation.  Although koi spawn each spring, and regularly live 50 years and beyond, the bright and shiny ones are most likely to be seen and eaten, and it doesn't take long for the balance to tip in favor of the better-camouflaged individuals.  The ornamental koi that we all love are literally dependent upon us to exist.  
We need to provide them with safe habitats.  The biggest part of this is the act of creating an isolated body of water that is free from predatory fish, a.k.a. a water garden or koi pond!  Controlling what goes in the pond allows people to create bubble-environments that would not occur in nature.  This freedom from the stress of predation has given the ugly old carp the opportunity to thrive, and to express itself in ways that would not be safe out there in the wild.  You could think of the beautiful colors a koi wears as its way of thanking us for giving it a good home.  

This is a photo of our first pond during a drain & clean; the arrow is pointing to the fish cave. You can see it is both the lowest and most secure area in the pond. This is done on purpose. In the winter koi will go to the lowest part of the pond, so we made that part the most secure to keep them safe while they hide from the cold.

​To create the best home for koi, there are a few important criteria your pond should meet.  

1. Make the pond at least 2' deep.  This gives the koi enough depth to go beyond the reach of most predators.  Raccoons, for instance, do not like to get their head under water, and prefer to use their sensitive paw-hands to find their food.  Even better than 2' is 3', but you don't need to dig the entire pond to that depth, a 3'x4' area that is 3' deep will be enough room to provide the koi a safe zone at the bottom of the pond.  
2. Build a fish cave for the koi to hide in when they feel threatened.  The Landvista Aquascapes approach to fish caves involves utilizing large flat rocks atop a pair of medium-size boulders.  Imagine a Stonehendge monument, but much longer, that's sort of how we build a fish cave.  We like to set it against the edges of the pond where it blends into the surroundings, rather than in the center where it would stand out.  
3. Marginal plants.  This one is easily overlooked, after all, how would plants on land make a difference under water?  The answer is that the plants along the edge of your pond provide shade and cover, and they create a place where it is difficult to access the water.  Fish may swim up near the plants, and the plants will obstruct the any animals on land from getting too close.  Another benefit of marginal plants is that all the bugs falling into the pond off their leaves and stems creates a new food source for your fish. 
4. Aquatic plants, especially floating plants like lily pads, lotus and water lettuce, create excellent cover in the pond and give your fish nice pockets of shade where they can hide.  Aquatic plants are crucial to any pond ecosystem, and the cover they create for fish is an essential part of this symbiotic relationship.  

A net like this over your pond can help keep your koi safe from predators, and it also keeps leaves out of the water.

We consider sufficient depth, hidey holes, and plant cover as critical elements in a good pond.  They are excellent first-steps to take when creating a safe koi-environment, but they are not the only precautions you may take, we know of a handful of other tricks that are also of some benefit.  

• Decoys.  Based on experience, the most effective decoys for koi ponds are decoys of heron and alligator.  Herons are territorial birds, and they will avoid a pond that appears to be hosting another heron.  They are not dumb birds, however, and will notice if a decoy is always in the same place day after day.  The trick is to keep moving your decoy around to a different location.  Moving it once a day would be great, but every 2-3 days will still be effective.  Gator decoys are good for scaring off mink and other mammals, and you don't have to move them around.  They can also be effective against herons on the ground, but because alligators are well camouflaged, they may not be noticed by herons in the sky.   
• Noise.  Wild animals are instinctively cautious, and will usually scurry off at the sound of a knock or a tap.  We use a bamboo knocker fountain that works like one of those drinking birds: as water pours into the top of the bamboo it eventually outweighs the other end and tilts down, knocking into a shorter piece of bamboo and pouring out its water, which flips the balance and it tilts back up to start the cycle over again.  This is especially effective against deer, whom may not pose any danger to your koi, but are known to reduce a lush hosta to frayed stems in a single night.  
• Sprinklers.  This one goes along with noise, as the splashing from a sprinkler or fountain has the same startling effect on animals.  You can hook up a motion sensor to a sprinkler so it only activates when something approaches, greatly enhancing the surprise-factor.  Just remember that it's there or you might wind up startling yourself!  
• Netting.  The same netting that we use during the autumn to keep leaves out of our ponds may be used year-round for pest-prevention.  This usually works fairly well for birds, not as well for for mink.  A determined critter can still claw its way under or through the netting.  
• Fencing.  Some people have such a problem with mink killing their fish that they place a fence around their pond.  This certainly makes a difference, but being a relatively unappealing visually, this option is mostly used as a last resort.  
• Dogs.  It doesn't have to be a big guard dog that sleeps outside, (although that would certainly be most effective) even a little pet terrier will help.  The reason is because wild animals have excellent noses.  They can smell that there's a dog living there, and they will tend to avoid the area.  This isn't a guarantee, plenty of people with dogs still fall victim to mink stealing their koi, but it does make a difference.  Outdoor cats can also help guard against mink or weasel, but are little help against larger predators like fox, possum, raccoon, and coyote.  Although cats and fish are not exactly best friends, pets often develop a kinship or at least tolerance towards each other.  It is possible that your cats may become protective of your koi, but it is equally possible that they prey on your fish themselves.     

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Landvista Aquascapes has a great team of pond experts that designs, builds, services and repairs beautiful koi ponds in the South Jersey area. Landvista Aquascapes is based in Atco, NJ and loves working on water features in the towns of Medford, Marlton, Mt. Laurel, Moorestown, Mullica, Maple Shade, Mt. Holly, and Mantua.  We adore backyard ponds in  Tabernacle, Tavistock, Shamong, and Sicklerville.  We are your go-to waterfall contractor in Voorhees, Westhampton, Waterford, Winslow, West Deptford, and Woodbury Heights.  Landvista Aquascapes builds safe homes for koi in Haddon Heights, Haddonfield, Hammonton, Hainesport, and Hi-Nella.  Landvista Aquascapes fixes koi ponds in Berlin, Cherry Hill, Deptford, Egg Harbor, Franklin, and Gloucester.  

Thanks for the algorithm love, Google!