Mycobacteria in Fish

Over the last few months, our office has seen several cases of mycobacteria. Never heard of it before? Well, here’s everything you need to know:

Mycobacteria in Fish

Depending on your fish experience, you may have heard a lot or very little about the potential dangers of mycobacterial infections. This disease can be very hard to diagnose without proper pathology processing and can persist in seemingly healthy systems for years. Clinical signs are very vague and can be augmented by other problems with your tank. Of all the diseases fish can potentially contract, this one can be passed onto HUMANS. Due to the severity of this disease, we’re here to set the record straight and make sure all fish owners know the ins and outs of this disease.

What is mycobacteria?

Mycobacteria is most commonly associated with tuberculous. It persists in almost all aquatic environments as a non-harmful environmental contaminant. Some species, however, can infect fish, including M. marinum, M. fortuitum and M. chelonae. M. marinum can be found in both freshwater and marine environments. It is spread through direct contact and release from the internal organs post-death.

What are the clinical signs of infection with mycobacteria?

Unfortunately, the clinical signs of a mycobacteria infection are very vague. It is most commonly associated with wasting, loss of body condition, lethargy and anorexia. Other signs include scale loss, skin ulcers, a dropsy-like appearance, reproductive problems and a host of secondary infections.

How is a mycobacterial infection diagnosed?

Mycobacteria is diagnosed in fish through a biopsy of internal organs sent to an aquatic pathologist. There are no tests that can confirm mycobacteria in live fish at this time. The presence of mycobacteria is confirmed using an acid-fast stain.

What treatments are available for mycobacteria?

The saddest part of this infection is that no treatments are available for a mycobacteria infection. Fish can persist with this bacteria in low stress environments with good water quality, but will eventually succumb to the disease. It is recommended the entire system be decontaminated with a carefully selected disinfectant that will penetrate the mycobacteria. Not all disinfectants will work with mycobacteria. Prevention is key through proper quarantine and possibly sacrificing some individuals for histopathology screening.

Is mycobacteria dangerous to humans?

Yes. This is one of the fish diseases that can be passed onto humans. Although the disease is rarely life-threatening, the bacteria can easily enter any open cuts or sores that are placed in tank water. Take proper precautions and avoid contact with tank water and do not allow other pets to drink the water.

What do I do if I think my fish may be infected?

It is extremely important that mycobacterial infections be diagnosed as early as possible. Contact your local aquatic veterinarian or aquatic pathologist to get your fish tested. ( or Remember, there is no testing available for live fish, so you may need to sacrifice a sick individual to confirm.


Francis-Floyd, R. 2011. Mycobacterial Infections of Fish. Southern Regional Aquaculture Center.

Francis-Floyd, R & R Yanong. 1999. Mycobacteriosis in Fish. University of Florida IFAS Extension.

Barley Straw in Koi Ponds – What’s it all about?

If you have any experience with keeping koi in large outdoor ponds, you’ve had some experience with algae. Controlling it is not always an easy task. Throughout your struggles, you’ve probably heard something about barley straw and extract. How does this work and what’s it all about?

The Science Behind Barley Straw

The exact mechanism of how barley straw works is still unknown. As the barely straw breaks down, it releases compounds that keeps algae from growing, especially string-type algae. Although it will stop the growth of algae, it will NOT kill it. Killing algae will need an additional UV filter or chemical additives.

Is it safe for fish?

Barley straw is the safest algae deterrent available for koi ponds. Adding barley with a UV light will take care of the bulk of your algae problems.

What is the difference in the formulations?

Most products involving barley come in three forms: hay bales, pellets or liquid. The hay bales should be kept in a mesh bag to keep the individual straws from floating into your filtration. Pellets are usually compressed hay in shorter lengths. Both the full bales and pellets will take 3-5 weeks to start being effective. The barely straw needs to be broken down in order to start stopping algae. Liquid extracts bypass this step by doing the breakdown in advance.

When should I add this to my pond?

The best time of year to add barley is before your warmer months and throughout the summer. By starting to use the barley straw prior to the biggest algae growth season, you can stop growth before it starts. Read the instructions carefully on any product before you start to use it.

Five Years of Fish Fun

Five years to the day, something that has never been done before got started. The FIRST veterinarian to pursue an all-aquatic veterinary practice, not on the side or part of a previously established veterinary practice, opened her clinic doors. No one had ever heard of this specialty before. Not in California or many other states. And not only a veterinarian, but a traveling one that could show up and take care of things pond or tank-side. We didn’t have a single client for over 2 months. Our first year, we had 53 appointments for 29 clients. We now have over 350 clients and almost 50 appointments in our first two months, even with our chief vet being out for 3 weeks. Our range started with Santa Cruz and Santa Clara counties. We now cover 22 counties and have traveled as far north as Roseville and south as Torrance. That’s 420 miles of 800 miles total for California! We never mind the far drives. We know how important our services are to fish owners everywhere!

Our staff has grown from a one-person operation to a two business hospital/store with 5 total employees. Expertly trained by our veterinary leader, this staff is a wealth of fish knowledge and can solve most common husbandry problems without veterinary intervention. Our hospital manager, Sara, is started on her vet tech degree, and can triage most callers issues before the vet even knows about them. Our answering service is an amazing addition to our team. They talk to our callers and can send us a detailed summary of all the calls coming into the hospital. It allows us to filter these through and decide which calls get priority. When we started, we got a call or two per week. Now, there are days when our phones don’t stop ringing. We just can’t get to everyone at once, so the answering service helps us out immeasurably.

And don’t forget our publications! Our children’s book series, Boo & Bubbles, was started to make sure that families had all the correct information regarding adopting a pet fish. We see countless instances where some prior knowledge or general help with basic husbandry issues could have solved problems swiftly. Our first book, Boo & Bubbles, addresses tank setup, bringing your fish home from the store and acclimation. The second, Boo & Bubbles: A Visit from the Fish Vet, covers maintenance and what to do when your fish gets sick. It is the first appearance of a fish veterinarian in literature. The third, to be available this coming April, will cover quarantine and adding fish to the same system. This is a very accessible children’s series that needs to be a part of any new fish family’s library. Our koi book, Healthy Koi Made Easy, just came out with its second publication, updated with new pictures and chapters. This highly accessible koi manual covers all topics new and seasoned fish owners should know, including water quality, signs of disease and quarantine. It is available in softcover, PDF and on Kindle.

It has been a very challenging five years since our inception. We are attempting a business model with no plans or blueprint. Other veterinarians have tried aquatic medicine and settled on making it a side profession. We are modifying that plan and paving the way for future veterinarians to bring aquatic practice into their hospitals in any way possible. All fish deserve high quality veterinary care, and we will make sure it happens. In the last five years, our company his made a lasting impact on the veterinary profession, and we will continue to do so for the next 5, 10, 20, 50, 100 years and on.

Thank you for your support.

Dr. Sanders at the 2014 ZNA NorCal koi show meeting all the wonderful fellow koi enthusiasts

How Do Fish Undergo Surgery?

One of the most common questions we get asked is how do fish undergo surgery? Yes, even surgical treatment is available to fish. It can be a simple lump removal all the way through to a full open abdomen procedure. It is simply amazing how well a fish improve from a simple corrective surgery.

Are they awake for the procedure?

Absolutely not! Just like people, cats and dogs are sedated for surgery, so are fish. Rather than using an aerosolized anesthetic, fish are sedated using a water-based anesthetic. Our office uses a compound called MS-222 or Tricaine-S (tricaine methanesulfonate). Other fish vets may use eugenol or clove oil. These compounds produce a safe plane of anesthesia to operate with the fish happily in dreamland. Recovery using clean water usually occurs within 10-30 minutes.

Surgery on the stomach of a shovelnose catfish

Are the fish underwater when you operate?

No again. For simple external procedures, the fish will lie on one side with the surgical site up in the air. Usually we have an assistant or net hold the fish partially submerged. For open abdomen procedures, we have a specially crafted, acrylic V-shape that fits over a 10-gallon aquarium. An aquarium pump moves water from the reservoir below, through a tube to the fish’s mouth, which then flows over their gills and back down. It is a very simple closed circulation system that works extremely well. (Modified through the amazing work of Drs. Harms & Lewbart). There is one person assigned to this job for the entire surgery and monitors the fish’s anesthetic depth through gill movement and heart rate.

Our specialized surgical rig

What is the craziest surgery you have ever done?

Well, we do a lot of procedures that are very odd for the general veterinary practitioner. Given the specialty of our service, we see nothing but “odd” cases. Some of our favorites include our fish friends Rocky, Lemon and Sparky. Read all about their cases here.

Watch some of our procedures on our YouTube site: Eyeball Removal, Abdominal Tumor Removal

Have more questions? Check out our Fish Surgery FAQ

Fish X-Rays

A few months ago, we first met Huxley and Darwin. They are both moor goldfish with big, bulging eyes and short, stubby bodies. Huxley is red and Darwin is black. When they first presented, Darwin had a growth on his dorsal fin and Huxley was on his belly at the bottom of the tank. A quick water test reveled that their water had a low pH, high ammonia and very low kH (alkalinity). This is commonly referred to as Old Tank Syndrome. Usually caused by a lack of maintenance, this case was compounded by the source water with a low kH as well. Darwin had the mass along his fin removed and changes to the maintenance procedure were made.

A few months later, Huxley (red moor) presented for lying on his side, a change from his belly-sitting behavior previously. Knowing the issues fancy goldfish can suffer with their anatomy, Huxley’s owner brought him to Westside Animal Hospital in Santa Cruz, CA who we partner with to perform radiographs, also known as x-rays. To perform radiographs on fish, they are sedated using a water-soluble drug, then picked up out of the water and positioned on a plastic sheet on the radiograph table. We use plastic bags and bubble wrap to make little slings to keep them straight up and down. They are only out of the water for approximately 20-30 seconds and then returned to the sedation water while the radiographs process. Here is what we found for little Huxley…


Huxley – Right lateral

Huxley – Dorsoventral

There’s a lot going on in these radiographs, and can be very confusing for those of us who have never seen an animal radiograph before, let alone one of a fish. Here are some more fancy goldfish for reference…

You’ve heard Rusty’s story before, but here are his radiographs

You’ve also met Lemon before

And here’s a comet goldfish for comparison…

This fish presented with a pebble stuck in its mouth. Can you find it?

All fancy varieties of goldfish originally descended from the standard comet goldfish. Can you see how their anatomy has changed to suit their external appearance? Most notable is the swim bladder. Fish have internal air balloons called a swim bladder that helps them maintain neutral buoyancy. Most carp species, including koi and goldfish, have a cranial and caudal air sac. You may note in the fancy radiographs, they only have one or in Rusty’s case, one almost on top of the other. It is completely normal for fancy goldfish to only have one air bladder, and it may even appear over-inflated. This over-inflation is an adaptation to limited tail movement. These goldfish have been bred for beautiful external features, not room for normal internal anatomy and swimming behavior.

What is most apparent on Huxley’s radiographs is the shape of his spine. Not only does it take an odd “W”-shape appearance, but two vertebrae have luxated (red arrow) or possibly fractured.

Before presenting, although negatively buoyant, Huxley was able to maintain an upright position by using his tail as a kickstand. However, following these radiographs and a neurological exam, Huxley has lost function of his tail and therefore is resigned to stay on his side. His owner is very diligent and has switched his substrate for smooth glass beads that do not irritate Huxley’s skin or grow bacteria. Huxley still has a ravenous appetite and likes hanging out with Darwin.

These cases are always hard for our staff and clients. Huxley will never swim like a normal fish. He will be on his side at the bottom of his tank for the rest of his life. His owner is aware of this and understands his limitations. The decisions concerning these cases are ultimately the owner’s paired with veterinary recommendations.

Fancy goldfish may be very beautiful, but their internal anatomy often causes secondary issues with buoyancy and visual disorders. Many of these bubble eye varieties will scar down from tiny tears. Internal anatomy limitations from external body features can cause swim bladder issues and affect buoyancy. When considering your next fish to adopt, remember that these fancy fish may be hiding a secret inside that may affect their livelihood as they grow bigger.

Koi Herpes Virus – What You NEED to Know

Koi Herpes Virus. Those three little words can spell disaster for any koi owner. Koi herpes virus is a viral infection that can kill 95-100% of exposed koi in 24-48 hours. Quarantining any new additions can keep KHV from spreading to established populations. With warm water and transport stress, fish will become sick and die quickly, but since they are quarantined, they will not spread the disease to your other fish.

In the cyprinid (koi and goldfish) herpes family, there are 3 known viruses. Cyprinid herpesvirus-1 causes carp pox. Carp pox is a skin disease of koi that causes irregular growths usually around the dorsal fin in koi. Cyprinid herpesvirus-2 is a disease in goldfish causing hematopoietic necrosis of the internal organs. Cyprinid herpesvirus-3 is the causative agent of the deadly koi herpes virus. The virus causes severe necrosis of the gills and other internal organs. Death occurs quickly, within 24-48 hours.

Koi owners need to be aware that KHV is present and deadly. Without proper quarantining procedures, all the fish in your pond can be decimated. Any new additions to any pond should be quarantined separately for minimum 4-6 weeks. The incubation period for KHV is 7-21 days. New additions need to be quarantined with new koi to make sure they are not a carrier. Carrier fish will never show physical signs of the disease, but can transmit it to other fish. Goldfish and other carp species can be carriers and NEVER show any signs of illness. Be sure the water is between 60⁰-77⁰F (16⁰-25⁰C) to bring out the virus if it is present. If your new additions are indeed carrying KHV, they will sicken and die quickly, but your other fish will be protected. Any fish that survive an outbreak of KHV are carriers of the virus and can spread it to other fish. It is recommended that carriers are isolated for the remainder of their lives or humanely euthanized.

So how do koi get KHV? Koi can get KHV through direct contact with infected fish or their fluids as well as contaminated water, mud or equipment. Once they contract KHV, the sick fish usually show unspecific signs of illness, most commonly, sudden death. Post-mortem analysis of fresh dead fish can confirm an outbreak of KHV. If there is suspicion that a fish may be a carrier of KHV, there is another test available that can confirm the presence of KHV in live fish from a blood sample.

KHV is a reportable disease to the state and OIE. It is not an actionable disease, like Spring Viremia of Carp, meaning that euthanasia of survivors is NOT required. It is up to the owner and veterinarian to decide what will be done with any survivors.

Unfortunately, there is no treatment for KHV. A vaccine was previously available, but has since been discontinued. The best thing to prevent KHV from spreading is quarantine. Quarantine all new fish additions for 4-6 weeks in water 60⁰-77⁰F (16⁰-25⁰C).

If you suspect your fish may have KHV, contact your local fish veterinarian IMMEDIATELY. In California, call (831) 346-6151. To find a fish veterinarian in your area, review the following databases.

American Association of Fish Veterinarians –

World Aquatic Veterinary Medical Association –

For more information, check out this handout from UFL or e-mail

Why Test My Water?

As you have heard us say, time and time again, water quality is the #1 thing pet fish owners can do to take care of their fish. Why is this? Because, just like the air we breathe, the water a fish swims in has a significant impact on its overall health. Poor water quality can cause severe problems with secondary bacteria or fungus, swim bladder disorders and even death. It may sound like a lot to undertake, but we’ll make it easy. We have several helpful guides around our website (here, here and here) and great brochures you can order. Want more? Check out our awesome Water Quality Webinar!

How do I test my water?

You’re going to need a test kit! Yes, there are convenient test strips available, and are better than nothing. Keep in mind, however, that we’ve tested these products and gotten conflicting results on different strips right out of the bottle! A liquid, drop-based test kit is a much better option and they are not too hard to use. Once you practice using them a few times, it will become very easy.

What parameters do I test?

When testing fish water, your nitrogen cycle parameters are the highest priority. These are your ammonia, nitrite and nitrate. pH and kH are extremely important as well. And don’t forget your thermometer! Fish activity and metabolism is directly linked to water temperature. Unlike us endotherms, able to regulate our internal body temperature, fish are ectotherms and rely on the water temperature to dictate their activity.

How often do I test?

With fish systems that have been in place for at least 3 months and have no changes to equipment or inhabitants, monthly testing is highly recommended. With systems that have new fish or other animals or new equipment within the last 3 months, such as pumps or filters, weekly testing is recommended.

What results are within parameters?

For koi and goldfish, your pond or tank should be within the following parameters: (These readings are based on the ranges given by the API Freshwater Master Test kit)

Ammonia: less than 0.25 mg/L, Nitrite: 0 mg/L, Nitrate: less than 40 mg/L

pH: 7.0-8.5, kH: above 100 mg/L, Temperature will vary seasonally

Tropical fish will have species-specific tolerances for ammonia, nitrate, pH, and temperature. Most communal species will be within the same ranges as koi and goldfish, but the temperature must stay between 75-85F.

Betta fish have a higher tolerance of ammonia and nitrate, but that doesn’t mean they don’t deserve a clean tank. Temperatures must be kept at 78-82F for betta fish. (Want to learn more about bettas? Check out our Betta Page or Betta Basics Webinar).

Can you recommend a good test kit?

Absolutely! For most pond and tank owners, we recommend the API Freshwater Master Test Kit with kH and a thermometer. We have full kits available at our Fish Vet Store.

Webinars On Fish Health

Want to get more great fish health information? Check out our webinar series!

New, upcoming webinars can be found on our Fish Vet Store page.

Past webinars can be found on our YouTube page.

Happy learning!

The Dreaded White Spot Disease

Ich, white spot disease or more formally Ichthyophthirius multifiliis, is one of the most common freshwater parasites. It is a protozoan parasite and can cause 100% mortality if not treated quickly. Unlike some other parasites, only one of these can cause a major problem. As a fish veterinarian, I perform skin and gill biopsies commonly. If I were to see a few Trichodina or monogenean treamatodes (flukes), it is not concerning and does not warrant treatment. However, just one ich parasite can produce over 1000 offspring! This rapid reproduction can overwhelm a system and its inhabitants very quickly. Infections most commonly occur when a new individual is added to a tank/pond and not properly quarantined. Remember, you will save a lot of time, money and lives by quarantining all new fish for 4-6 weeks before adding them to your existing system.

Ich reproduces through a complex lifecycle. Starting as a trophozoite, the protozoan feeds on epithelial cells of the skin and gills. When it has eaten enough energy, it moves onto an encapsulated phase, called the tomont. This stage is protected by a capsule that adheres to fish, plants, substrate, or anything in your pond. Within the capsule, the tomont divides by binary fission until there are over 1000 theronts, which then break out and become the feeding trophozoites.

When treating for Ich, you must take its complex life cycle into consideration. Most treatments specific to Ich only treat the free, feeding stage (trophozoite), not the encapsulated form where the parasite divides. Therefore, a two-step or prolonged treatment is required, the length of which depends on the temperature of your system. In 77⁰F water, it takes only 3-6 days for one trophozoite to produce its 1000 offspring. However, at 59⁰F, it takes up to 10 days. The length of time for the life cycle to complete increases the colder the water gets. Keep this in mind while trying to gauge how far to spread apart your Ich treatments.

Most commonly, outbreaks of Ich occur in the spring was the weather starts to warm. Fish stocked at higher densities will develop outbreaks faster since there is more tissue for the trophozoites to feed upon. Clinical signs of Ich are most commonly white spots on the skin and/or gills. Sick fish may show general signs of illness which include sitting on the bottom of their tank, lack of appetite or reddening of the fins. Definitive diagnosis is made by observing the encapsulated form whirling under a microscope. Fish may show signs of flashing (scratching their bodies on objects in their tank) with some bruising along their sides.

There are a few different treatments available, but make sure to remember to treat at least twice or continue treatment for the length of at least 1.5 life cycles. Possible treatments should include formalin, formalin/malachite green, copper or salt. There are many commercial products available to treat Ich specifically. Make sure to check the ingredients so you know what you are adding to your tank. Remember that copper is toxic to ALL invertebrates and salt can kill freshwater plants. For more information on how to diagnose and treat Ich, please contact our hospital.


Secrets to A Cleaner Fish System

Proper fish tank or pond maintenance takes patience to learn but is easy to master. Once you find a routine that works for you, your water will always be perfect and your fish will thank you for it.

Not to mention all the money you’ll save on veterinary bills!

Identify the different parts of your system and follow the water flowing through all your components. (**hint: draw a picture!!**)

Know how to safety turn off your system without overflowing or running pumps dry. If your system is maintained by another person or company, have them show you how to do this. If there is ever an emergency, you need to know how to stop everything, just in case.

Identify what maintenance needs to occur daily. For outdoor ponds, this usually includes skimming debris off the surface or emptying your skimmer. For saltwater tanks, you probably need to top off with freshwater daily.

Identify your mechanical and biological filtration components. Mechanical filtration physically removes debris and includes settling tanks, mesh screening, drum filters, floss, etc. Biological filtration are specific media where good bacteria is cultured. This good bacteria is essential to converting your fish’s ammonia waste into safe nitrate. (Don’t remember this? You need to watch our webinar!) When cleaning these components, you DO NOT want them sparkling clean! Cleaning biological filtration too thoroughly can reset your filters to ZERO.

Routinely remove old water from your system and replace with new, fresh, clean water (What you hear us refer to as a WATER CHANGE, or backwash for certain filter types). The size of your system, the amount of fish you have and your filtration capability will determine how often this needs to occur. It is important to watch your water parameters and learn how your system changes daily, weekly, monthly, seasonally, etc.

Learn how to clean up after your fish. In a tank, you will need to master how to use a gravel siphon. Ponds may require the use of a pond vacuum. Many YouTube videos are available on how to operate the many various types of siphons and vacuums available. (Need a gravel siphon? They’re part of our WATER QUALITY TESTING PACKAGES. Available now for a limited time!) Using the siphon or vacuum also counts as a WATER CHANGE!!

It may sound like a lot of steps, but I promise, you CAN DO IT!

If you need assistance, contact a local fish tank/pond cleaning professional and have them teach you the steps. If you want, they can do all the hard work for you, leaving you with the easy job of simply enjoying your fish.

Click Here for a Daily/Weekly/Monthly Tank Cleaning Checklist

Click Here for a Daily/Weekly/Monthly Pond Cleaning Checklist

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