Top 5 Most Common Problems with Koi Ponds

Koi make up the majority of our veterinary practice, and in seeing so many cases, some common themes occur. Don’t make the same mistakes with your fish!

  1. Not Checking Your Fish Daily – We know in the winter, when metabolisms are quiet, your fish are not very entertaining. However, even in the slower, winter months, small problems can start to grow very quickly, especially when the weather starts to warm. Even though you may not be feeding your fish daily, it is critical to check on all the fish DAILY to make sure they are doing okay.
  2. Not Testing Your Water Quality – This rule does not apply to fish tanks alone. Koi ponds can suffer the same New Pond and Old Pond syndromes and a whole host of other issues. Water quality is the #1 important factor in fish health and is the leading cause of secondary disease. Buy a test kit, learn how to use it, and keep track of how your pond changes with the seasons. Learn more about water quality here.
  3. Adding New Fish without Quarantine – This year will have a significant increase in Koi Herpes Virus cases. Protect your fish by quarantining ALL NEW FISH for at least 4-6 weeks. DO NOT expect your dealer/vendor to do this for you. Most parasite outbreaks come from new fish being added to a pond without quarantining first. Watch our Koi Herpes Virus webinar here.
  4. Feeding an Appropriate Diet – There are many, many, many different koi foods available and they are NOT all created equal. Read through the ingredient list carefully and understand what all the different nutrition labels mean. Watch our helpful webinar so you can make the best choice for your fish. Maintenance, Growth, Color-Enhancing, etc do NOT mean the same thing throughout the different brands. And “nucleotides” is a completely idiotic label. Do you know what nucleotides are?
  5. Keeping Up with Your Maintenance – In winter, we know things slow down and maintenance routines can relax. However, this is not an excuse to completely ignore your pond! You should at MINIMUM keep up with your backwashes to keep your pressurized bead filters functioning properly and keep your skimmer and matting free of debris. Click here for a complete checklist of pond tasks.

If you have ANY concerns about your koi at ANY time, contact your local aquatic veterinarian. If you are in California or Nevada, call us at (831) 278-1081. We will have our Spring Pond Package ready to roll as soon as spring hits. Schedule your visit today!!


Top 10 Mistakes New Fish Owners Make – #6

The #6 Mistake – Not Storing Fish Food Properly

What is the best way to store any pet food? Rather than roll up the bag and toss it in the corner, all pet food should be kept in an airtight, opaque storage container in cooler temperatures of a pantry or closet. And fish food is no exception.

Also keep in mind that fish food starts to lose water-soluble vitamins, such as vitamin C, as soon as you open it. Within a few months, there is barely any available vitamin C left. (Sources here, here and here.) Vitamin loss can be prevented by properly storing your fish food. All fish food should be kept in an airtight container, in a cool place out of the sun.

Fish Flakes

Due to their high surface to mass ratio, fish flakes lose vitamin C faster than any other fish food. If your fish can handle a pellet, switch them over. These days they come in very tiny sizes!

Fish Pellets

Most of these products now come in light-proof, re-sealing pouches, which is great! Keep them in a cool place out of direct sunlight to keep them in good condition.

Koi Food

Even though your koi live outside, your food should not! If it is not in a re-sealing bag, keep all food in an airtight container in a cool place, out of the sun.

Since the temperature of a koi pond can vary widely, make sure you are feeding a temperature-appropriate diet. Higher protein foods are fed with warmer water.

For more on fish nutrition, check out our Fish Food Nutrition webinar:

Top 10 Mistakes New Fish Owners Make – #7

The #7 Mistake – Feeding Your Fish Too Much

One of the more common “healthy” pet issues we see in all of veterinary medicine is obesity, and fish are no exception. They may have better control than your golden retriever, but overfeeding your fish can have more severe consequences than just rounder fish.

Unfortunately, there is no absolute calculation to tell you how much to feed your fish. It depends on their species, temperature, water quality, other stressors, the type of food, formulation and current disease processes. For cats and dogs, it all depends on body size and life stage. If you take any bag of cat or dog food and look at the back, it will tell you what life stage the food is intended for and what amount to feed for body weight. (This assumes that your pet is the correct weight for the body type and structure.) But when was the last time you weighed your pet fish? Fish should be fed based on body size, but we know this is an impossible task for most owners. Thankfully, fish are pretty good at determining when they are full. A bigger problem is what happens when there is too much food in the tank.

So what should I do to ensure my fish are not overfed? We recommend using the 5-Minute Method. It is very simple:

  1. Sprinkle a little bit of food into your tank. We recommend mixing it close to the filter return so all fish can get a fair share.
  2. When all the food is eaten, sprinkle a little bit more. If the food is not completely consumed, WAIT.
  3. Continue for 5 minutes or until the fish stop eating.

NOTE: Some species, like betta fish, are not great at regulating their intake. Keep in mind that their stomachs are about the same size as their eyeballs. Only a few pellets once or twice a day is adequate!

Why does this method work?

The biggest problem with overfeeding a fish tank is not just fat fish, but increased stress on your biological filtration. The breakdown of fish food, since it contains a lot of protein, causes an increase in the ammonia levels in your tank. Using this method makes sure that the food ends up in the fish, not the bottom of their tank. If you’re unfamiliar with ammonia and the nitrogen cycle, read this explanation.

For more information on fish food in general, watch our webinar.

The Green Pea Myth

Constipated goldfish is the most widely over diagnosed case on the internet. There is not ONE peer-reviewed published paper about goldfish constipation and its treatments. Most commonly, goldfish “constipation” is misdiagnosed as a cure all for a sick fish. And in comes the main treatment… shelled green peas!

What is it about these tiny green globes of goodness that make most fish rise up from the almost dead?

One: They have almost no protein whatsoever, decreasing the amount of ammonia waste from your fish, decreasing the strain on your nitrogen cycle. Decreasing the ammonia waste from your system will make ANY fish better. Every 100 grams of green peas contains 5.4g of protein. Compare that to 100g of commercial fish flake and pellets having between 32-45g of protein.

Two: Green peas sink in water, therefore making fish dive to the bottom of their tank to eat, preventing excess air from ending up in their GI and swim bladder. Goldfish are physostomous, with a duct connecting their esophagus to their swim bladder. Considering the anatomy of some fancy goldfish varieties, these ducts are extremely short and therefore more air is able to get into the swim bladder, causing positive buoyancy issues. When fish eat at the surface, slurping food down like pigs, they can take in a lot of extra air. By feeding sinking peas, they don’t suck in as much air.

Three: Goldfish “indigestion” can be caused by an inappropriate diet. Goldfish, like all other carp, are omnivores, eating plants, bugs and almost anything tasty that fits in their mouths. In feeding them a flake or pelleted diet, you are aiming for a balanced diet. There are sooooo many fish foods out there, and a lot of them are based on educated guesses rather than actual research. As a fish owner, it is up to you to evaluate your fishes’ food to make sure it is appropriate. We have our most watched webinar on this very subject of reading fish food labels. Many of these “constipation” problems are from feeding very old food. After 6 months, your fish food has lost enough of the water-soluble vitamins, including vitamin C, that you are essentially feeding your fish cardboard. Getting a fresh bag of food, or switching the diet to our green peas (full of vitamins!), fixes almost all of the fish “indigestion” cases we see.

But what about all that fiber? 100g of peas contains 4.8g of fiber and most fish foods contain 3-5g of fiber, so it’s not really all that more fibrous.

All in all, peas are a low calorie treat that fish can enjoy. But are they magical, cure all tablets of greeny goodness? Sorry, but no.


What do I feed my fish?

If you own any pets, I guarantee you have fallen victim to pet food marketing. It happens to all of us, even veterinarians, causing us to question the education we received on just this topic. “Grain free,” “gluten free,” “all natural,” “organic” and other buzzwords are dropped at lightning speed to confuse the consumer into purchasing based on just how many of these words can fit on a package. And fish diets are no exception. Sure, they may not get the press of the cat and dog food, but a lot of little containers can fit into a very small shelf, causing fish owners eyes to glaze over just taking in the sheer magnitude of choices. Many owners will be drawn to either the flashiest packaging or cheapest price. It’s just a fish, right? Well, just like the food you eat yourself and feed to your fluffy pets, fish rely on good nutrition in order to stay healthy. By purchasing a quality fish product, you can improve your fishes’ lives significantly.

So how do I choose a quality product?

The best consumer is an informed consumer. We have a great webinar that is recommended by many of the top fish food companies. It breaks down how to read the labels on the back of fish food containers. There are considerably less items to peruse than your regular box of supermarket crackers.

Don’t have time to watch? Let’s break it down to the simplest parts.

Pellets vs. Flakes

This rule is easy to follow. If a pellet fits into your fish’s mouth, go with the pellet. This is due to surface to mass ratio and water soluble vitamins. Consider how much contact a flake has with the air and water in comparison to a pellet. A big, wide flat flake will lose more of its water soluble vitamins, including vitamin C, faster than a concentrated pellet. No matter how long the container has been open, pellets win.

The 6 Month Rule

I don’t care what is printed on your container; after you break the bag or jar open, you have 6 months to feed that food, then toss it. At the end of those 6 months, the water soluble vitamins, again, are so reduced, you might as well be feeding your fish cardboard. Those dates are printed on the outside in the event the store doesn’t sell the food by then.


This is listed on the ingredient list as “crude protein,” “crude fat” and “crude fiber.” This does not refer to petrol and is instead the method of testing.


All animals need protein to survive. Fish can be herbivores, omnivores or carnivores. Herbivores and omnivores need between 35-45% protein in their food. Carnivores require 40-55%. The protein source must contain all essential amino acids for the fish to live. The best source of these for fish is animal protein, specifically fish meal. Fish meal is any leftover fish scraps from processing fish into other products, mostly for human and cat consumption. Fish meal is perfectly safe and healthy. The best plant source is soy, but this can only make up 50% of the total protein. Soy does not contain all the essential amino acids fish need to survive.


Fats are used for energy, insulation and hormone production. In most fish, fats should be 15-25% of the total diet. Just like humans taking fish oil supplements, fish also require N-3 fatty acids that they cannot fabricate themselves. Vegetable oils have very few N-3 fatty acids. Fish can become obese with overfeeding, so try not to feed your fish your love!


The primary energy source in food is poorly digested in fish. High levels of carbohydrate rich treats can actually cause liver malfunction. Omnivores should only have 25-40% of their diet from carbohydrates, whereas carnivores require <20%.


Fish require most of their water and fat soluble vitamins from their diet. This includes vitamins A, C, D, E & K. Vitamin A deficiencies can lead to skeletal deformities, and lack of vitamins C & E decrease immune function. As we mentioned previously, these vitamins are the first nutritional component to leech out of food pellets and flakes.

Minerals (ASH)

No, ash does not mean that charcoal particles are mixed in as filler. Ash measures the mineral content of the diet. Most fish get their minerals from the surrounding water, so there is very little need for supplementation in the diet. Phosphorus is one of the main requirements from food, but only 0.3%.

Spotting Quality Food

Consider the various protein sources in a bag of fish food. If there are additional protein supplements listed, or multiple protein sources, this indicates a poor protein source and therefore, poor quality diet. Know the scientific names of all the vitamins and make sure your food contains all the essentials. A “vitamin mix” is perfectly acceptable.

Color Enhancing Food

Some koi diets contain color enhancers to bring out the red pigments in the skin. This is done through the addition of carotenoids, including synthetic materials, yeasts, bacteria, fungi, krill/shrimp and algae. These foods should be few very sparingly and only a short period of time.

How much to feed?

You’ve heard of our 5-minute rule, yes? You can apply it to all fish, not just koi. Always consider the size of the stomach in a fish. Provided you are not reading this zoomed in, the stomach on your betta fish is only this big –> o It’ll only take 4-5 of the tiny pellets and 1-2 of the larger pellets to fill that stomach. Bettas are repeat offenders for eating too much and not being able to pass large balls of poop. We are happy to recommend different feeding strategies based on your system.

If you have any questions about fish food, please contact our office directly: or (831) 346-6151

Top 5 Fish Mistakes – #3: Poor Nutrition

Top 5 Fish Mistakes – #3: Poor Nutrition

Fish medicine has come a long way in the last few decades and with that comes more knowledge about what fish a supposed to eat. Long gone are the days of flake-only diet. You have options for pellets, frozen food, live food, on and on for any species you desire to keep. A little bit of research goes a long way in order to provide your fish with a decent diet. Check out for a good comprehensive view on what your fish is supposed to be eating.

Keep in mind the size of your fish. Note how big their mouth is. If they can’t get their mouth around the food you feed them, they will not be able to eat! For tiny fish, flake is the best all-around staple diet. It can be supplemented with live or frozen food if you prefer. For medium size fish, pick a diet that is appropriate to their species and mouth size. Fish with large mouths can be fed a wider variety of foods, but they need a fish-pellet diet to stay at optimum health.

Once open, fish food will not keep for more than 6 months. Keep that in mind when purchasing your bag of food. You will need to use it all in 6 months. Flake food degrades even faster, due to its increased surface area. The first component to break down is vitamin C, an important component in health and immunity. Other vitamins follow soon after, so make sure you’re replacing your food every 6 months.

How much are you feeding your fish? Like our land-based pets, sometimes we feed our love to our pets, causing them to gain excess weight. We recommend checking out our feeding guidelines to give you some starting points. Remember that fish metabolism is temperature dependent!

Need some feed suggestions? Check out our store, Santa Cruz Koi!