Salt in Fish Systems

Salt is a normal component of many fish systems. Saltwater and brackish systems require salt on a continual basis. But what about freshwater systems? Some internet pages recommend keeping salt in koi/goldfish ponds/tanks at all times. Others say don’t bother. What are the effects of salt on an all-freshwater species?

In a freshwater environment, a fish’s body is more dense than the surrounding water. As a result, water is constantly trying to enter the fish’s body and achieve osmotic homeostasis. A fish’s gills, kidneys and urinary systems are responsible for removing the excess water. When these mechanisms are compromised, the clinical manifestation of “dropsy” can occur. By adding salt to the water, you are changing the osmolality of the environment surrounding the fish, thereby decreasing the amount of water diffusing into the fish. Some people figure this is less stressful for a fish, but after millions of years of evolution, it really isn’t necessary. A fish’s body can handle the metabolic demands of freshwater. It’s the human equivalent to drinking less water so your kidneys don’t have to work as hard.

Most salt-avid fish keepers will keep their fish in very low salinities: 1-1.5%. This level can be very hard to test accurately for and will often vary between 0-3%. This level will not hurt your fish. If you feel like you NEED to have salt in there, that’s fine, but you should not strive for levels greater than 2%. You do NOT HAVE to add salt to your freshwater fish system. Always add non-iodonized salt (not table salt)!

For some parasites, depending on the species and water temperature, higher therapeutic levels of salt can be used to treat the infestation. Salt works by first increasing, then depleting the mucus coat, which many parasites use as a food source and for protection. Once the mucus coat is gone, the single-celled parasites rupture from the changing osmotic gradient. But if you are slowly bringing your salt levels up without realizing it, some parasites have been found to become resistant to therapeutic salt levels, requiring treatment at even higher doses. The higher the salt dose, the harsher the treatment for the fish.

All in all, a little salt is fine, but don’t obsess over it. Your fish will do just fine without it. The only time we recommend salt is for recovery from trauma or surgery. Don’t forget that salt can kill aquatic plants!


Pond Bottom Cleaning – Best Practices

Now that we’ve covered all your potential options for pond substrates, how is the best way to go about cleaning the bottom of your pond? Here’s the full checklist of tasks for all ponds to keep up with on a daily/weekly/monthly/yearly basis.

If you have rocks on the bottom of your pond:

To prevent the buildup of dangerous anaerobic bacteria, stir your substrate weekly. If the rocks are larger, use a pond vacuum to suck the muck out from the bottom. To make the job easier, start to scoop out the rocks.

If you have a concrete bottom or liner:

Gently sweep any debris and algae towards your bottom drain a few times a week. If you do not have a bottom drain, use a pond vacuum to suck up all the debris after it settles post-sweep. Be careful with liners not to scrub too vigorously or else you may rip a hole!

If you don’t ever clean the bottom of your pond:

Time to start! If you think there is more than a few inches of mud at the bottom of your pond, get your fish out of the pond and in a temporary holding tub just in case you have pockets of hydrogen sulfide. Dig down until you hit the liner or concrete bottom. Try to keep up with cleaning on a weekly or at least monthly basis to keep it from being such a chore!

If you do not have a bottom drain:

Never fear! Even if you didn’t add a bottom drain when you put in the pond, one can be retrofitted. Bottom drains make cleaning ponds so much easier! Contact your local pond professional to get one added to your pond today!

What’s at the bottom of your pond?

There are many ways to build a koi pond, and some methods can affect your maintenance regimen. Your pond bottom, also known as your substrate, can dramatically change how much time and effort you spend cleaning your pond. We’ll cover some of the most common bottom covers and the pros and cons of each

Gravel/Small Rocks

Pros: This substrate is the most eye appealing of them all. It breaks up the industrial look of a synthetic fish environment and can provide hold for and uncontained plants.

Cons: You will need to stir the gravel/small rocks frequently to keep them from cementing together. A pond vacuum will be of little use and will keep collecting all these small stones. This substrate collects lots of debris and is hard to clean. If the substrate is deeper than 3″, you run the risk of anaerobic bacteria production once they are cut off from the oxygen in the water. This can create pockets of hydrogen sulfide that can kill fish if mixed into the water supply.

Large Rocks

Pros: Another aesthetically appealing bottom substrate. Larger rocks are more suitable to a “river” appearance.

Cons: Your pond vacuum will work slightly better if the substrate is too large to fit up the hose. If the stones are too heavy, you will have a very hard time cleaning between them. Multiple layers of stones will be more likely to collect debris than only one layer of rocks. This layering effect can contribute to cementing of rocks together and formation of hydrogen sulfide producing anaerobic bacteria.


Pros: A liner bottom is one of the easiest substrates to keep clean. They work well with a bottom drain.

Cons: Pay special attention to the thickness of your liner. Thinner liners may be more economical, but they will not last as long as thicker liners. They are prone to tears from rocks, root growth and boots. They are not as aesthetically pleasing and deep folds can potentially trap fish.

Concrete/Spray Liner

Pros: Concrete bottoms with a spray-applied liner are very easy to keep clean. They are more durable than simple liner ponds. Leaks from tears are not an issue as this type of bottom stands up well to abuse from rocks and boots.

Cons: This is one of the most expensive substrate options for fish ponds. If your concrete is not mixed properly, you will lose chunks of your bottom, leading to leaks. They are susceptible to earthquake damage if this is an environmental concern. Be sure both your concrete mix and spray liner are appropriate for usage with fish. You cannot change the shape of your pond or add any underwater features later with this substrate.

Plants/Mud/Bog/”All Natural”


Cons: Your lack of cleaning effort creates a dangerous health hazard to your fish. Dense planting and layers of debris and fish waste create layers of bacteria that lose contact with oxygen in the water. These anaerobic bacteria use sulfur as a food source. If you mess around in the muck or your fish try to flash on this surface, you will release hydrogen sulfide and kill all your fish.

It is impossible to recreate a native environment in a synthetic fish system. “All natural” systems in wild environments use multiple species working together to balance waste management. In a man-made pond, you are missing many of these critical elements. Do your regular maintenance!

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.

pH and kH

It’s time for everyone’s favorite topic: water quality!

Many of our clients purchase “master” test kits which include: ammonia, nitrite, nitrate, low and high pH. This is a great collection of parameters to start with, but what about kH?

For those of you unfamiliar with kH, kH measures the buffering capacity of your water. Buffers bind to free hydrogen ions (H+) and keep them out of solution. Since your pH is a direct measure of [H+] in your system, kH directly impacts pH. And remember that high [H+] = more acidic and low [H+] = more basic.

(For those of you who are confusing this with gH, or total hardness: gH measures the amount of calcium and magnesium in your water. Although this may be a component of your kH, they are separate parameters entirely.)

So, if your kH levels are too low, all the H+ your fish discharge due to metabolic processes can build up and crash your pH. Adequate kH levels will keep your pH consistent throughout the day, regardless of what your fish and filters are doing. Knowing your tanks kH is an essential component to any fish keeper’s database. There are simple tests available that will make your testing a true “master kit.”

A kH value of >50 mg/L is adequate, but >100 mg/L is better. 

If your tank kH is low, test your source water kH. Some city and well systems have low kH coming in and will need buffers to be manually added to your system to maintain adequate levels. Keep an eye on your pH when manually adding buffers in order to make sure your pH will not change too much. Slow and steady is the goal for any pH changes.

Troubleshooting Fish Systems

Troubleshooting Fish Systems

Many of the fish issues we see at Aquatic Veterinary Service condense down to one thing: ineffective husbandry. Most of the time, it is not the owners fault and they receive false information from many conflicting sources. Well, we’re here to set the record straight and make it easy to take care of your fish. The better care your fish receive, the better their overall health and fewer calls to the veterinarian!

Fish Troubleshoot #1: Test your water.

For those of your loyal followers, you know how important water quality is to fish health. Most of the issue we see would have been avoided completely if the water parameters had been maintained. Test kits are available for cheap and are very easy to run. At the first sign of distress: CHECK YOUR WATER!

Fish Troubleshoot #2: Water changes.

All fish systems need regular water changes. I don’t care what that internet forum told you. If you imagine the wild fish populations, their water is never stagnant or contained. It is constantly flowing in, out, up and around. Fish kept in ponds and tanks are in artificial systems. They require new water every once in awhile to flush out not only nitrogen products, but hormones and other waste that is impossible to see with the naked eye. Never done one before? Well, we’ve created a helpful guide to show you the way.

Fish Troubleshoot #3: Clean your damn tank.

Are fish low maintenance? Well, you don’t need to walk them or potty train them, but they do require regular care and maintenance. If you do a little bit weekly, it will make the whole process easier. A cleaning protocol should include: scrubbing walls, removing waste and excess food, rinsing filter media and cleaning decor. We have handy checklists for both ponds and tanks that you can tweak to create your perfect protocol.

Fish Troubleshoot #4: Temperature.

Fish are ectotherms. This means that unlike your fluffy mammalian pets, they cannot regulate their internal body temperature. Their body temperature, with the exception of larger ocean-dwelling fish, will be the same as the water temperature. Different species of fish have specific tolerances for temperature. Goldfish and koi, can survive in just above freezing temperatures all the way up to 90F! However, some tropical fish can only do 77-83F. Know your species temperature tolerance and make sure you have a good thermometer in the tank at all times. And stick on ones do not count!

Fish Troubleshoot #5: Diet.

Not all fish eat the same things! Commercial diets might seem all-inclusive, but these can be misleading. Some fish can be very picky eaters while others would eat your tires if given the opportunity. Research the diets of your fish and if you can’t find any conclusive information, try to offer variations including pellets, vegetables, fruit, bugs and frozen diets. Flakes are great for small fish, but graduate them to pellets as soon as possible. Pellets have less surface to mass ratio, meaning that all the nutrients won’t be leached out as soon as they hit the water! Many food packages are labeled with an expiration date, but this applies only if you don’t open the bag. As soon as a bag or jar is opened, you must toss the remainder after 6 months. After 6 months, a lot of the vitamin content has broken down, so you’re essentially feeding cardboard.

Fish Troubleshoot #6: Personality clashes.

Just like people, cats and dogs, not all fish will get along with each other. Usually, this comes down to species territoriality, but we see it result in fighting over food, space and mates, often resulting in injury and death. When setting up a tank, always make sure the fish you’d like to home together will get along or have enough room to feel safe. If aggression develops over time, you will need to rehome the bullied or the bullier. Unfortunately, there is no effective behavioral therapy for fish… yet.

Stick to these key points and your fish will be happy and healthy for years to come!

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

The Princess and the Pond

The Princess and the Pond

In every veterinarian’s career, there will come cases that try us mentally, physically and emotionally. For us here at Aquatic Veterinary Services, we have been tested by a case that we battled for almost 6 months. What started as a simple lesion steamrolled into a serious bacteria problem for multiple large koi.

Princess, a 28″ kohaku koi, had been moved with 5 of her pondmates from Redding last fall down to Carmel. Early in their acclimation, one of the koi got sucked up into the filtration and was killed. The fish were moved temporarily to another pond for a few weeks before the problem could be fixed and the fish returned. One of Princess’s cohorts, Whitey, started to have a small red spot on her nose. In addition, Princess started to have a red mark next to her left pectoral fin. Physical exams showed a penetrating pectoral ulcer on Princess’s left pectoral muscle. Princess received an antibiotic injection and would receive a re-check in a few weeks.

Princess (left) & Whitey (right)

A few weeks later, Princess’s wound had not improved and now Whitey also had signs of a nasty ulcer on her right pectoral muscle. A culture was taken from Whitey’s wound and the owner elected to treat with an aggressive 8-hour dose of potassium permanganate. Due to the high algae load in the pond, the first PP treatment required two smaller, follow up doses in order to keep the pond purple for the full treatment. Even with the treatment, the fishes’ wounds did not start to improve. In fact, two other fish in the pond were starting to show signs of a persistent infection. One had fractured a fin ray that caused a massive hole and the other’s eyes started bulging out.

Well, when the culture results arrived, we found out why the fish were not responding. Two drugs, out of the dozen processed, would be able to kill the Aeromonas spp. present. Two, out of a panel of twelve. One of the drugs would cause kidney failure if used at too high a dose. The other was only available as a powder for oral dosing. We were able to make up a medicated feed with the powder, but unfortunately, the fish decided that it was not to their liking. Some drugs are very noxious and fish will not eat them, even when we try to hide them with flavorings. So, that left us with one drug, but only one dose taking careful weight measurements so as not to incite kidney failure. All 5 fish in the pond received injectable medications.

Did it work? Not really. Many of these drugs require repeat doses in order to be truly effective. At this point, we were left with very, very few options. This is the part where I stay awake at night thinking, ‘what else can I do?’ Thankfully, when we were trying to come up with some sort of alternative plan, the powder antibiotic was finally available as an injectable! We bought as many vials as we could and we managed three rounds of injectable meds.

Keep in mind that all of these injections were done in the pond without sedation. We also had to give all of these fish physical exams every visit, without sedation. You try holding a 25 lbs slippery rocket made of pure muscle and see how long you get to stab it with a needle. I am so proud of myself that I was able to give these fish the care that they needed with the limited options we had available.

Long story short: every fish is now on the mend. Are they healed entirely? No, not yet, but all of the wounds are showing great signs of proper healing. Thanks to their very patient owner and our unwillingness to give up. These cases don’t come around very often, but when they do, we are so glad to report a happy ending for this pond.

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


No Pond Quick Start

Putting in a new pond comes with lots of challenges. You built it perfectly with great filtration and put in the most amazing fish, but your ammonia is off the charts and you can’t get your filter to start cycling. (Cycling is the process wherein good bacteria convert toxic ammonia to toxic nitrite to safe nitrate.) There are many products out there that claim they can “quick start” your pond and get it cycling faster. Well, we’re here to tell you that these quick fixes do not work.

After trying several products to get our own hospital tanks cycling, we were forced to wait not-so-patiently until they started cycling naturally. Most systems will start to cycle between 4-6 weeks, MINIMUM (temperature dependent). To prove this point, the first day we tested positive for any nitrite was EXACTLY 4 weeks to the day that we added fish to our tank. We added several different products to our 4 separate hospital tanks to try and speed this process up, but to no avail.

The only way to ensure a faster start is to take biologic media (mats, beads, etc) from a pre-existing, cycling system and add them to the new biological filter. Since we were starting from scratch across the board, this option was not open to us. Keep in mind: differences in water chemistry and temperature can cause changes in your bacteria colonies. Transferring established media to a pond with very different water chemistry and temperature variations will not do you any good and will kill the pre-established bacteria.

Sorry, but you’re just going to have to wait.

Review your nitrogen cycle!
Review your nitrogen cycle!