Why Are My Pond Fish Hiding? Guide to Koi Shyness & Solutions (updated)
One of the most frustrating problems with a fish pond is not being able to ever see the actual fish! Fish that hide all day can make a garden pond seem empty and lifeless, especially when they’re supposed to be the main attraction. Although this is often a common problem with newly introduced fish, it can also be a problem with older fish who have been a part of your family for a long time.
There are numerous reasons why koi and goldfish may become skittish or go into hiding, and it can be difficult to determine the exact cause. The reason could be a single issue, such as a shyness in a new environment, or a combination of many issues making an older fish stressed and skittish. Luckily, for most common causes, there are things you can do to help re-build confidence and give them a friendly nudge out from hiding.
Are koi more skittish than goldfish?
Both goldfish and koi can demonstrate skittish behavior, although we find that koi are more susceptible to a sudden change in behavior even when they have been comfortable for a long time. This is because koi are more sensitive to changes in the environment than goldfish, and may become stressed or frightened under certain conditions. For example, a changing water pH or rising ammonia level in the water will likely start to affect koi sooner than goldfish, so you’ll notice a change in behavior first in your koi.
Sometimes fish also just need some “downtime” to de-stress, and they should start to acting normally again after a short period of hiding away. This applies to both koi and goldfish, and should not be a problem unless the behavior continues for more than a few weeks.
If there is a sudden change in behavior or things just aren’t getting better after a long period, you may need to take a closer look at your pond to try to determine if there is a problem present.
Common Reasons Koi or Goldfish Hide
1) Newly Introduced Fish
Probably the single most common reason for fish to start hiding is if they’re newly introduced to a pond and haven’t had time to get used to their new environment. This can happen in both brand new ponds after adding multiple fish, or when you add a single new fish to a mature pond alongside your older fish. In both cases, the fish have just had a huge change in environment, and this can be quite traumatic to both koi and goldfish.
After adding a new fish to your pond, it’s actually very common for them to hide and act shyly for a few days while they slowly begin to explore their surroundings. This hiding behavior should not be considered a problem unless it continues for more than a few weeks, or you notice the fish is not eating any feed you provide. Even if the fish doesn’t eat with you close, it will likely begin eating when you retreat to a further distance from the water. Typically new fish shyness resolves on its own in time, so is not usually something to worry about.
2) Predator Attacks
Another common and more serious problem that may be affecting your fish and causing them to hide is attacks from predators, such as herons. Even if you don’t notice any predators in your garden, this doesn’t mean they’re not paying your fish a daily visit! Herons, for example, usually visit ponds during the early hours of the morning or right before dusk, so unless you’re around during these times you may just be missing the action. Telltale signs of predator attacks on fish are missing fish, damaged scales, injured fins, and fish that are constantly hiding. During an attack fish will instinctively retreat to the deepest point of the pond for shelter, and they may remain there longer and longer each time unless the threat is removed. Predators will also cause stress for pond fish, which over time, may start to affect their general behavior and confidence.
3) Changes in Water Quality (pH/Ammonia)
Maintaining good, stable water quality is one of the primary goals of fish keeping, and a change which affects the overall balance can cause fish to act strangely or even become sick. The term “water quality” refers to a number of different layers which make up healthy pond water, with the most important being pH, ammonia, nitrite, KH, and GH. For pond fish, and in particular koi, keeping these levels stable and within a safe range is very important for fish health. A sudden swing in pH, or a rise in ammonia, for example, can cause huge stress on fish and force them into hiding. Testing water annually or at the sign of problems (hiding fish) is good practice, as an imbalance in substances could easily be a factor for newly skittish behavior. Rapid changes in pH and a spike in ammonia are often the most common culprits in these cases.
4) Poor Quality Fish Food
One of the best times to say hello to your fish is during feeding sessions, and in most cases, your fish would agree! However, if you’re feeding koi or goldfish a low-quality fish feed they may slowly become less interested over time. This is especially true in mature ponds with heavily planted environments, as fish likely have a more nutritious source of food from insects and plants. Selecting a food that meets your fish’s requirements is important, as well as making sure the primary protein source is aquatic-based. Many low-quality feeds will have a primary plant-based protein source to lower costs, as well as other “filler contents,” and sometimes fish are just fussy unless it’s the real thing!
5) Sickness or Parasites
Strange fish behavior or a newly skittish fish may have a problem with parasites or a bacterial infection. A fish that feels under the weather will naturally separate itself from the group and seek shelter in a quiet part of the pond, away from everything going on. They may start refusing food, and spend more time hidden away from other fish. If you notice this kind of behavior, your fish may have a growing infection or parasite problem which may require treatment.
6) Stagnant Pond Water
If your pond is stagnant without good water flow, your fish could be suffering from low oxygenation. Pond fish require large amounts of dissolved oxygen to breathe and may become sluggish and unresponsive to food in water with low levels. As well as this, beneficial bacteria need oxygen to break down harmful substances, such as ammonia, and cannot function efficiently without it. This could lead to rising ammonia which may also be stressing your fish. If your pond has no water features, a weak pump, and you notice algae growth is rapid, you likely have insufficient aeration.
Steps to Make Fish More Confident
Step 1: Add Fish Shelters
For newly introduced fish there is little you can do to prevent them from hiding until they grow used to their new environment. Generally, this behavior will only last a few days, but can be prolonged if the fish is constantly stressed and has no “safe space” to retreat to. Funnily enough, one of the better ways for a new fish to grow in confidence is to make sure they have a place to hide!
If a new koi or goldfish has nowhere to de-stress after a sudden move, it will just take them even longer to adjust to their new pond. Providing plenty of hiding spots and shelter for fish to relax is a good way to speed up the transitional period. A fish which feels safer and more relaxed in a new pond will be more quick to adjust and gain confidence, even if that means hiding for a few days.
Heavily planted ponds should provide a good amount of natural coverage, so you likely just need to give your fish time to get used to their new home. Ponds without natural coverage may benefit from the addition of a man-made fish shelter. These are designed to provide a safe hiding place for fish, allowing them to escape predators and to de-stress when needed. They will also likely become a new fish’s best friend for the first few days they’re introduced, and you’ll often see them in the shelter while they get used to everything. We highly recommend them for open ponds with little natural hiding spots or coverage.
Step 2: Implement Predator Deterrents
Predator attacks from herons, hawks, cats, or raccoons can have a serious and long-lasting effect on pond fish. If a predator is hunting fish daily, they will become less and less confident in their own pond and will start retreating to deeper water for extended periods. They may also become more wary of humans and other animals around the water, and try to avoid swimming close to the surface.
The best way to prevent predators is with deterrents designed to scare away the animals before they have a chance to catch your fish. Most deterrents are aimed towards stopping herons, but they will also work for other predators by making the garden and pond less inviting. Popular deterrents include decoys, netting, shelters, fencing, and automatic water and sound devices. Depending on how confident the predator is in your garden, you may be able to scare them with just a single method or you may need to implement a range of different approaches. The most effective in our experience are a combination of pond netting, fish shelters, and automatic “scarer” devices. Having all of these deterrents at once will stop all but the most stubborn of predators, but you can try one method at a time to see what works.
Check here for our full guide on heron and predator deterrent methods and what we consider the best choices for ponds.
Step 3: Test and Improve Water Quality
Rapid changes in water quality or a gradual imbalance can cause fish to become stressed, sick, and go into hiding. Testing water quality at the first signs of problems will help you determine if the cause is related to your pond’s water chemistry. Common culprits are a high or low water pH, and a rise in ammonia levels. Both of these measurements, and more, can be calculated using a water testing kit or an electronic pH reader. These tools can provide accurate readings for a range of water measurements, allowing you to determine if your pond is within safe parameters for fish keeping.
If your pond is having problems with ammonia or pH it can usually be resolved before too much harm comes to fish, although the most important thing is to make sure everything is as stable as possible! Sudden swings are much more dangerous than gradual changes, even when trying to fix a problem. It’s better to maintain a more stable environment and slowly improve things than to try to adjust water quality quickly with a “quick fix” treatment.
For more information on the ideal water measurements and how to test them, check our guide on testing pond water here.
Step 4: Try a Different Fish Food
Fish may start turning down food which is low quality or has too much filler content, and you may mistake this behavior as the fish hiding from you. In a matured pond fish have plenty of natural food sources, so unless the food you’re giving them is particularly tasty, they may start turning it down more often.
Feeding time is a good way to get better acquainted with your fish and build a strong and confident relationship. Pond fish who love their food will also love you for providing it, and they’re unlikely to stay hidden long when it’s dinner time. It’s important to interact with your fish daily during feeding as this is the single best way to gain their confidence and reduce hiding if they’re scared of you.
If you notice your fish aren’t taking as much food as usual when you’re actively feeding, or turning down food altogether, we recommend switching up their feed. A fish food with a high quality aquatic protein source is preferred as this is a more natural diet, and most fish prefer it over plant proteins. In general, a quality fish feed should be 30% protein, 3-12% fat, and have minimal ash (filler) content. This range will provide optimal benefits for growth and strong immune systems, with as little waste as possible.
For recommendations on quality koi foods and more information about the ingredients, check our article here.
Step 5: Treat for Parasites and Infections
A sick fish will instinctively break away from the group and try to find shelter elsewhere in a secluded part of the pond. Fish with parasites or infections may start acting strangely, often sluggishly, and become very uninterested with food.
If you notice a sudden change in behavior that is accompanied by your fish hiding regularly, you can treat them for both infections and parasites to be on the safe side. Common parasites, including flukes and tapeworms, can be treated safely with Aqua Meds Prazi treatment. Bacterial infections can be remedied with a wide-range treatment which helps improve the fish’s immune system and promotes recovery. We recommend API Pond MELAFIX for both new and mature fish to treat infections such as eye cloud, fungus, and fin/tail rot.
Treating for infections and parasites is a big part of fish keeping, and is usually something pond owners will perform every winter and spring for optimal health. These kinds of treatments also work well after a predator attack to help improve recovery and prevent open wounds from becoming infected. Most treatments contain natural active ingredients and will not harm or stress your fish, so you can use them safely on a regular basis if needed.
Step 6: Improve Aeration and Filtration
Stagnant water with low oxygen content or a poorly filtered pond makes for very unhappy pond fish! If fish are hiding or don’t want to know, it could be that they’re trying to tell you something is wrong with the water. Both goldfish and koi need plenty of oxygen to thrive, and will become slow and even sick when levels get too low. Oxygen is also needed for beneficial bacteria to break down harmful substances before they can build up and become a danger to fish.
As well as this, ponds need a good filtration system, and sometimes the eco-system can be improved simply with better filter media or additional bacteria to supplement the process. If you have many fish in your pond, you should also ensure your filter box is large for effective filtration. As a general rule, you cannot “over filter” a pond, so the bigger the better in terms of fish keeping!
If your pond has little aeration, you can consider adding a water feature or an air pump which will add both flow and oxygen to the pond. To improve filtration, you can try optimizing your filter media, adding activated carbon to remove chemicals, or supplementing with more beneficial bacteria.