How do you know if a fish is sick?

We’ve already established that fish get sick, so how can you recognize when something is wrong? Signs of illness can be broken down into two categories: physical and behavioral.


These indicators of illness can be very easy to spot. Physical signs of disease include:

  • Changes in coloration
  • Bumps/lumps
  • Asymmetrical body shape
  • Misshapen fins
  • Wounds
  • Ulcers
  • Etc, etc etc

Most of the times, these changes are fairly obvious, but especially in the case of coelomic tumors, subtle changes can be very hard to spot. Here are some examples of physical signs of disease:


Behavioral signs of disease are harder to spot. If you don’t check your fish out every day, these signs can be very difficult to spot. A 5-minute fish viewing session twice a day is recommended at bare minimum. Behavioral signs of disease include:

  • Incorrect body position
  • Negative/positive buoyancy
  • Avoiding areas of tank/pond
  • Hiding/unsocial (species-specific)
  • Swimming behavior
  • Flashing
  • Non-seasonal change in appetite/feeding behavior
  • Etc

In order to recognize “normal” behavior, you may need to look outside your home pond/tank. What may be “normal” in your pond may be very obviously not normal if you watch other fish of the same species in a different environment. Call up the neighbors and arrange a pond/tank social hour at a different home each week/month!

If you have a behavior that you cannot identify as normal or abnormal, CALL A PROFESSIONAL. Our office number is (831) 278-1081. It is better to be certain than let a unknown behavior slide for too long.

For more information on spotting sick fish, including some behavioral indicators, watch our webinar:


Top 5 Spring Diseases in Koi

It’s almost koi season at Aquatic Veterinary Services! Here are our most common diseases we can expect to see and the signs you should be aware of if any of these diseases are present in your pond.

5. Carp Pox

Although not THE koi herpes virus, carp pox is also known as cyprinid herpesvirus-1. It causes lesions within the skin that can look like “candlewax drippings” and “frosting” along the leading edges of the lips and fins. In cooler water temps, the lesions can be severe, but as the water warms, the fishes’ immune system and skin replacement can make the lesions almost vanish. Only in severe cases will a fish start to be compromised to secondary infections.

Since this is a herpes virus, there is no treatment or cure. If you have one fish in your pond that is showing these clinical signs, all of your fish have already been exposed. Only immune-compromised or stressed individuals will show clinical signs.

This is a very common disease for us to diagnose. Unless the case is severe, the fish will have good health, but will not be very pretty.

4. Monogenean Treamatodes (aka ‘flukes’)

These irritating little worms are most commonly gyrodactylus or dactylogyrus species. They can infiltrate the skin or gills and cause severe irritation for any fish. You will most commonly see signs of skin irritation, with increased redness on paler fish, bruises or missing scales.

Since fish cannot itch themselves like a cat or dog, they exhibit a behavior known as “flashing.” Usually, you will see your fish throw themselves sideways along the sides or bottom of their pond in an attempt to dislodge these irritable invaders.

Severe infestations can cause the gills to shut down and death to occur. There are many over-the-counter medications that will claim to take out these bugs. Please keep in mind that these medications are not controlled or overseen by any government checks. A veterinarian can prescribe a prescription-strength medication to take care of your problem safely and easily.

Boo & Bubbles: A Visit From the Fish Vet

3. Gondal Sarcomas

Unfortunately, we often do not catch these tumors in time for surgery. Females between 8-12 years of age seem particularly more susceptible. Our Spring Pond Package for 2019 will include ultrasound screenings for all females since we are trying to catch this disease early.

The only physical sign you may see is a slightly enlarged, perhaps asymmetrical, body shape.

These space-occupying tumors most likely start from female gonadal tissue. By the time they are visible externally, most of the internal organs are failing. These masses are very hard to catch, which is why our new screening system will be started this year. If caught early, the tumor can be removed via surgery.

2. Trichodina

This aggressive “scrubbing bubble” is often aided by our #1 disease in koi. We tend to see this parasite most commonly, often displaying the same “flashing” behavior as our monogenean friends.

This parasite is easily treated by our prescription-strength medication. Over-the-counter medications do not work well against this parasite for some reason.

1. Water Quality

I know it is not a “disease,” but poor water quality is the #1 diagnosis for disease I make. Having poor water quality makes all diseases WORSE, including bacteria, fungi, parasites and other pathogens.

Water quality is directly linked to fish health. Like the air we breathe, the water a fish swims in has a direct effect on their overall immune function. Before the spring diseases come, get your maintenance routine overhauled and test your water chemistry regularly to make sure your fish have their best chance for a healthy spring.

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!!

“Reputable Dealers” Cannot Guarantee Healthy Fish

“Reputable Dealers” Cannot Guarantee Healthy Fish

Over the years, many of our clients have added fish to their pond without quarantine and denied any problems simply because the fish have come from a “reputable dealer.” Unfortunately, even our store, with some of the strictest quarantine guidelines, cannot guarantee our fish are 100% disease free.

Why is this? Well, keep in mind that fish live in a toilet. There are constantly pathogens on them, including bacteria, fungi and parasites. A healthy fish’s immune system works to constantly keep these invaders at bay, but they are always around in low numbers. This is why when water quality goes off the rails, we commonly see secondary infections. The stress of compensating for poor water decreases a fish’s immune function, allowing these pathogens to multiply and spread.

No dealer can 100% sterilize a fish. It would be cruel to even attempt it. But they should be able to keep you away from the worst. In fish, these are mainly viruses. Viruses, such as Koi Herpesvirus (KHV), can wipe out a pond very quickly. By ensuring a proper quarantine length and temperature duration, most dealers will catch infected fish and remove them from their purchasing pools. However, even if they say their protocol is one thing, unless you watch them go through this protocol, you cannot guarantee anything.

The only way to cover all your bases? Quarantine your fish yourself. A simple setup with separate equipment and filtration out of splashing range of your pond will guarantee that no sick fish are bringing anything into your pond. Read this article on quarantine or watch our webinar to make sure you can keep your fish healthy.

Preventing Disease in Fish Tanks and Ponds

Preventing Disease in Fish Tanks and Ponds

Everyone always wants to know how to keep their fish system from becoming infested with some horrible disease that puts all their fish at risk. Well, it’s a lot simpler than you think!

  1. Quarantine. Quarantine. Quarantine. This includes plants and ALL NEW FISH. The stress of handling and transport is enough to make even the healthiest of fish turn on your tanks inhabitants. Fish cannot be sterilized and always have pathogens on them, including parasites, bacteria and fungi. Most problems occur when new fish, invertebrates or plants are added to an established system. Set up a separate hospital tank and have it at the ready whenever new fish are on their way in. 4-6 weeks is the MINIMUM requirement for all new additions. For more information, be sure to watch our Quarantine Practices webinar!
  2. Maintain your water quality through consistent maintenance, proper feeding and adequate filtration. Water quality is the #1 thing owners can do to keep their fish healthy. Get a test kit, know how to use it and what normal parameters look like. Not all fish systems will be identical! Keep up with your maintenance. If everything is a bit discombobulated, use these handy checklists for tanks and ponds.
  3. Feed your fish a good quality diet that is species appropriate. Look for a food with appropriate levels of protein, fat and carbohydrates. We are happy to give consults on diet for FREE. If you want to learn more about fish diets, watch our webinar.
  4. Note any signs of disease early and take precautionary measures. You set up that hospital tank, right? Learn the physical and behavioral signs of disease in fish through our free webinar.
  5. If you think something is wrong, ASK NOW! Don’t wait until a small problem becomes big and hard to manage. Our job is to help you take care of your fish, plain and simple. We can work within your budget to make sure your fish get the care they need. Call us at (831) 346-6151 or email

Follow those rules and your fish will thank you! Being healthy and disease free is the way to be, no matter what your species!

How to Help A Sick Fish

How to Help A Sick Fish

“Help! I have a sick fish. What do I do?” is the most common question we get asked. Regardless of the issue, there are some things you should always do:

  1. Check your water chemistry. Low cost, reliable, at home test kits should be included in every new aquarium and pond setup. Make sure you use yours regularly and know how to properly read all the results. In a pinch, many pet fish stores offer free or low cost testing. Many issues that cause sick fish can be related to water quality. At the first sign of illness, test your water quality!
  2. Look at your fishes’ diet. Just like the food we eat affects our overall health, so does your fishes’ food. Most fish foods will start to lose their vitamin content after only 90 days! Flake foods will lose their vitamins faster due to increased surface to mass ratio. If you have some questions about what diet is best for your fish, ask your local fish veterinarian or pet fish store for recommendations.
  3. Check your other fish for signs of disease. There may be one susceptible fish in your tank or several. The number of fish affected will help indicate what illness you are dealing with.
  4. When was the last time you added new fish? Adding a new fish that was under considerable stress from transport and then dropped in an alien environment can bring lots of fun parasites and diseases into an established tank. Just like you bring home lots of new germs from the airplane ride with complete strangers, so does your new fish addition.
  5. Call a professional for assistance. Do not waste time falling into an internet black hole. Many seasoned fish hobbyists can help with general husbandry and diet issues. For disease diagnosis and treatment, you will need to contact your local fish veterinarian. We realize that there are currently many over-the-counter medications available, but keep in mind that these are not regulated products. No one is checking the contents of those little foil packets before you dump it in your tank/pond. Treating a fish that does not need medication can breed resistant strains of bacteria that can affect your fishes’ future health. For a list of veterinarians who see fish, check out the American Association of Fish Veterinarians and the World Aquatic Veterinary Medical Association.

Top 5 Mistakes Fish Owners Make – COMPLETE!

Our seminar on the Top 5 Mistakes Fish Owners Make is complete! Catch up on everything you missed:

Watch the Recorded Seminar

Read Our Articles

  1. Too Many Fish
  2. Disorganized Cleaning
  3. Poor Nutrition
  4. Limited Education
  5. Not Recognizing Problems

If you have any additional questions or concerns, please contact our office at (831) 346-6151

Top 5 Fish Mistakes – #5: Not Recognizing Problems

Top 5 Fish Mistakes – #5: Not Recognizing Problems

Do fish get sick? You bet they do! Fish illness can present itself in many ways. Most problems can be divided into two categories: physical and behavioral. Physical problems are the easiest to diagnose and involve physical changes in a fish’s appearance. This category can include open wounds, ulcers, lumps and bumps, color changes and changes in body shape, such as with dropsy or egg-laying females. Behavioral issues are changes in a fish’s everyday routine. This can include loss or decrease in appetite, odd swimming posture, changes in buoyancy or lethargy. Some of these subtler changes can only be noted with daily observations.

Fish owners are very attuned to their fish’s day to day routine, usually observed at feeding times. They note who is first to the food, who lingers behind or waits their turn and how all the fish swim around their tank or pond. If a fish is starting to become ill, an owner may notice a change in their physical appearance, or perhaps the fish that used to eat everything all the time has started to hang out at the bottom during feeding times, noting a behavioral change. Usually, a one-day slump is normal for a fish to have every once in a while. Just like people, fish can have off days where they return to normal the following day.

If a fish’s behavior has been altered for three or more days, it’s time to do some problem solving. We recommend checking your water quality to start and usually doing a water change regardless of the values. Most issues with fish that we encounter in our veterinary practice are actually secondary to poor water quality. Investing in a drop-based water test kit and testing weekly is a great tool for any fish owner. If the water checks out okay and the fish is not improved, it’s time for a deeper look. There are reference books available for those looking to educate themselves on fish health.

Here are some good reads, all written by fish veterinarians!

Fish veterinarians are a growing veterinary specialty and are happy to help educate fish owners on best practices and help out when there is a fish in distress. To find a fish veterinarian near you, check out the following two databases:

American Association of Fish Veterinarians

World Aquatic Veterinary Medical Association

We here at Aquatic Veterinary Services are happy to help with any fish questions even if you do not live in our immediate area. We are happy to help answer any fish questions that any fish owners need assistance with. We would much rather you turn to us than try to scour the internet and lose yourself off in a dark corner. Come to us and get the right answers the first time! 

Click Here to Get Help Now

The Realtor’s Guide to Selling a Home with a Koi Pond

The Realtor’s Guide to Selling a Home with a Koi Pond

Are you a realtor? Do you think it’s extra hard to sell a home with a pre-existing koi pond? Well, never fear! We’ve written the complete guide to selling a home with a koi pond: highlighting their many attributes while finding solutions to perceived challenges. Click HERE to download your copy or read on!

The Realtor’s Guide to Selling a Home with a Koi Pond

Many homes in the Bay area have koi ponds. Their owners hope that they will be able to sell their houses without having to remove their ponds and fish. Sometimes it can be challenging to sell a home and convince the subsequent owner that a koi pond is a benefit. This guide illustrates the benefits of owning a home with a koi pond. It also gives suggestions to mitigate the real or imagined challenges.


Nothing promotes relaxation like a koi pond.

Imagine taking your coffee/tea out to your pond every morning and simply observing your fish swim around.

Watching fish is a very meditative experience and good for your overall mental health. Studies have proven this:

Set up a lounge chair or small table near the pond in order to thoroughly enjoy the pond in full relaxation.

The sounds of the waterfall and other water features help calm the mind. Save money on sound machines and go for a much more natural option.

Your fish will love you.

Yes, it’s true! Koi have a broad range of personalities and will become very interactive at feeding time. We have owners who train their fish to eat out of their hands.

Fish will come to recognize each family members’ footsteps as they approach the pond. They can feel the difference in footfall vibrations through the pond. They will soon learn to swim over when they “hear” you coming! Children love them too!

Food motivation is a terrific training tool. Koi in particular can be trained very easily using food rewards. It may take some time, but they can be trained like any other companion animal. You can teach them to eat out of your hands and to swim over by name.

Amazing learning environment for children.

Kids love koi ponds, plain and simple. Being able to interact with aquatic animals in any environment is a fantastic learning Experience for children of all ages.

As they grow, children can become more involved in taking care of the pond, just like any other pet. Have younger children skim leaves off the top of the pond or assist in feeding the fish. Older children can help with tending aquatic plants and even basic maintenance operations, such as skimming leaves and cleaning skimmer baskets.

Rick pond


Cleaning the Pond

As with any other pet, koi need to be cleaned up after every once in awhile. If your pond is setup correctly, the maintenance will be extremely minimal.

Maintenance companies are available to help make ponds more manageable. Clients can clean themselves, or you can schedule to have the cleaning done for you.

Have the current owners write out cleaning instructions from their current routine and run it by a pond professional. Just getting their opinion can help ease the new buyers concerns about owning a pond.

Have a few business cards with quotes from maintenance companies already at the home in case anyone has any specific questions about costs.

Keeping the Fish Healthy

What do you do if there is a sick fish in the pond? Did you know there are veterinarians who specialize in aquatic animal medicine! If you haven’t heard of these vets before, you certainly aren’t the first. Veterinary medicine is branching out into many different specialties to better serve a wider array of clients and pets.

If you are currently along the central California coast, you have our very own Aquatic Veterinary Services of Northern California in your service providers! Our 100% mobile office now offers hospitalization for critically sick and injured fish of all types.

Our veterinary staff is also available by phone and email to answer general questions for all interested parties, including other real estate agents, sellers and potential buyers.

If you are outside of our service area, check the following databases for your closest local fish veterinarian:

American Association of Fish Veterinarians:

World Aquatic Veterinary Medicine Association:

Cost of a Koi Pond

If the pond is already built and its ecosystem established, the majority of the costs have already been taken care of. The cost of maintaining a pond is very minimal compared with building one.

Some costs to consider include: food and treatments for the fish, replacing any broken equipment, paying for a regular maintenance service (optional), and the cost of water.

In areas of water scarcity or during drought season in California, water costs can be the largest percentage of your koi pond costs. However, a correctly set up filtration system with a low bioload (# of fish/square foot) will require very little additional water.

  • Water taken out of the pond for regular water changes should be used to irrigate gardens and lawns. The nitrate in the water is the ultimate plant fertilizer!
  • Regular water quality testing should be performed in order to determine the frequency of water changes. Your local fish veterinarian or pond maintenance company can help you with this, or you can buy your own test kit online.
  • Pond plants can also help decrease the buildup of harmful compounds in the pond.
  • It is always better to have more filtration than the pond needs.

For More Assistance

If you or your clients have any additional questions, we are here to help!

SCK March Mag Pics-0683

Aquatic Veterinary Services

Of Northern California

(831) 346-6151

4061B Soquel Dr, Soquel, CA 95073


Q & A with Fish Veterinarian

Q & A with Fish Veterinarian

Q & A with a Fish Veterinarian

Jessie Sanders, DVM, CertAqV
Jessie Sanders, DVM, CertAqV

We had a chance to sit down with Dr. Jessie Sanders, chief veterinarian at Aquatic Veterinary Services of Northern California, to ask her a little about her job and career.

Q: Why did you want to be a fish veterinarian?

JS: I have always had a deep love of water and animals. I knew from when I was very young that I wanted to be a veterinarian. I did my undergraduate degree in Marine Biology and was fascinated with the animals that lived underwater. During my college years, I had the amazing opportunity to volunteer for Mystic Aquarium’s fish and invertebrate department. I had so much fun helping take care of the animals in their collection and always wanted to learn more. I followed their veterinary team closely and always wanted to be more involved in advanced animal care. From those volunteer hours, I figured out that I wanted to be an aquatic veterinarian.

Q: Where did you learn how to be a fish veterinarian?

JS: I attended Tufts University for my veterinary degree. Their exotic program was limited and they only had 2 lecture hours on fish medicine, so I was forced to create my own curriculum. I attended AQUAVET, a summer program for veterinary students on aquatic medicine offered through the University of Pennsylvania and Cornell University, and MARVET, another summer program offered through St. Matthew’s on Grand Cayman. During my senior year of veterinary school, students are encouraged to take externships off campus with other veterinary organizations. I had the privilege of working with the veterinary staff at SeaWorld Orlando, the Marine Mammal Center in Sausalito, CA, back at Mystic Aquarium and with Aquatic Veterinary Services of Western New York.

Q: How did you get your job?

JS: After veterinary school, I moved from Massachusetts out to California. I looked around for a “normal” veterinary job in a small or large animal general practice and came up empty after 6 months of searching. Seeing that there was a very large aquatic community in the central California coast area, I started my own mobile practice.

Q: How did you start your practice?

Our mobile unit
Our mobile unit

JS: With the mobile practice, it did not take much to get up and running. My mentor, Dr. Helen Sweeney, of Aquatic Veterinary Services of Western New York, gave me a detailed list of all the equipment I would need and a great database of fish medicine resources. Once I collected my equipment and filed for a business license, I was up and running in March of 2013.

Q: What type of fish do you treat?

JS: I treat everything that swims, including frogs and turtles! My main client base are koi and goldfish owners. Koi and goldfish are very hardy species and a very common pet in this area.

Q: How do you treat fish?

JS: We treat fish just as you would a cat or a dog, but with a few differences. Most of our exams start with catching the fish out of the tank or pond and putting them in a separate tub with some sedation. I am an excellent fish catcher thanks to years of practice. With the sedation, it is much less stressful for the fish to be handled since they are not used to it like a cat or dog. Once they are relaxed and sleepy, I can examine their outsides for any signs of disease and take samples of their skin and gills. These samples go under a microscope that I bring on the road with me.

Q: What about advanced treatment, like surgery?

Our in-house surgical setup
Our in-house surgical setup

JS: Fish can undergo surgery like any other animal. We mix the anesthetic into the water instead of aerosolizing it. My surgical assistant holds a tube in the fish’s mouth that pumps the water over its gills, keeping it asleep while I do the surgery. From a simple bump removal to invasive abdominal surgery, we’re equipped to handle it all.

Q: Why would you need to open a fish’s abdomen?

JS: My main species, koi, are prone to large tumors in their abdomens (coeloms). The only way to get them out is surgical removal. These tumors can be quite large, sometimes half the weight of the entire fish!

Q: What is a typical appointment like for a home visit?

Water testing while patient looks on
Water testing while patient looks on

JS: Like any other veterinary appointment, we start with getting a history on the current issue. Sometimes, it is just a simple health screening, where there are no current issues, but the owner wants to prevent them down the line. Other times, I will get called in to look at a particular fish or a few. We go over how the fish has been behaving, the duration, any past health issues, diet and water quality. I will commonly do water quality screenings during every visit, to make sure that whatever is going on with the fish is not augmented by poor water quality. Then, I will catch the affected fish and put them in the sedation tub for their exam. Small fish, such as bettas and goldfish, I can hold in one hand, so they usually do not require anesthesia. Affected fish will receive a full physical and any immediate treatment they require. Sometimes, we will take an unaffected fish out of the pond to compare to the sick fish. After the exams, we discuss the course of treatment with the owner and any improvements to their system that need to be made.