Aeromonas, The Alley and Dealing with them Both in Your Koi Pond

What is Aeromonas?

Aeromonas hydrophilia is a common pond water bacteria. So common in fact, it is found in every single pond. No amount of water changes or chemical warfare will get rid of it.

When not being an opportunistic pathogen, it is useful for helping to maintain good water parameters by digesting fish poop.

When introduced into an immunocompromised koi, it causes the damage that too many koi enthusiasts are intimately familiar with.

When this bacteria finds it’s way into a situation where it shouldn’t be, it causes a host of illnesses in koi. Ulcer disease, also known as Hole in the Side disease, is the most notable.

As the name suggests, as the disease progresses from a white, pimple-like spot on a koi’s body, it ulcerates and creates an open sore in and on the koi.

This furunculosis (or Ana aki in Japanese) is the condition that manifests itself in those blood-ringed , scabless ulcers that can cause loss of scales, permanent scarring, septicemia, internal infection and death.

Unlike some other diseases, Ulcer disease on one koi does not signify an epidemic amongst an entire population. Other koi may get it, but it will be for the same or similar reasons that the koi in question gets it, namely:

• poor water conditions (large pH variance, increased ammonia and nitrite levels)
• stress
• injury (scrape, scratch or chemical) resulting in an entry into the epidermis
• parasitic infection that causes the secondary bacterial infection

For more information on Aeromonas and how to treat it, you can read our article Aeromonas, Your Koi and What You Can Do to Combat It.

What is “Aeromonas Alley”?

Aeromonas Alley refers to the period of the year when winter makes way for spring and the water temperatures start to rise. It is usually in the 55-70ºF range.

As the water warms, Aeromonas bacteria become more active.  Koi immune systems also become more active, but at a much slower rate than the harmful bacteria.  This leaves a period where the bacteria are active and hungry for flesh to infect, while immune systems are still struggling to get up and running at peak effectiveness.  This is when Koi are most susceptible to bacterial infections.

Koi owners will be at their most vigilant when the water temperatures are in this range. Even those koi kichi in the warmer southern states have to remain vigilant. A pond doesn’t need to be frozen over to be at risk when spring rolls around. Temperatures can still drop into the 50s and stay there until spring starts—which means they will have to deal with Aeromonas Alley.

You may not be able to stop Aeromonas, but there are means of limiting and dealing with its capacity to become an issue for your koi when they are at their most vulnerable.

Medicated Food

This was often a topic of debate amongst koi enthusiasts. Some used it as a panacea for safeguarding against Aeromonas Alley (and other potentially harmful bacteria or health threats). Others believed it was all just so much marketing and a waste of money.

But it is now a moot argument, as the Food and Drug Administration has placed regulations on medicated feed for animals—including that in fish food. Only vets have the capability to prescribe antibiotic-infused medicated food. This has caused many food manufacturers to stop the production of medicated foods altogether.

However, there is an alternative to “medicated foods” that rely on prevention rather than “cure.” These probiotic-enhanced foods (like the Platinum Pro from Blue Ridge Koi and Goldfish) contain Primalac which have been scientifically proven to strengthen a koi’s immune system.

Blue Ridge has also released their new Probiotic Plus feed, with elevated levels of Vitamin C that boosts the immune system even beyond that of Primalac. Along with the addition of Montmorillonite clay (commonly known as koi clay), which introduces much-needed trace elements that pond water lacks, it is an all around great Spring purchase for a koi’s health. Probiotic Plus is a preventative food, meant to boost koi immune systems and prevent infection from ever getting started.

There are many koi enthusiasts who make their own homemade blends of vitamin and mineral enriched feeds. The formulae might be slightly different, but the principle is the same—slow down bacterial threats while their koi’s immune system gets up to speed. Like this one from Next Day Koi customer, Sandy Campbell:

I like to mix a gallon zip loc bag of koi food with concentrated real orange juice, just enough to wet the pellets but not soak them. Mix in a child’s crushed Vitamin C and an entire head of crushed garlic. Mix it all well and keep in the refrigerator. This can be fed a few weeks before winter and when they start feeding again after winter. It’s packed with Vitamin C. I also like to feed small pieces of kiwi fruit as it has more Vitamin C than oranges. All this boosts their immune system.

Going Indoors

This is not always an option for koi owners with space limitations or without the requisite components to be able to effectively house their koi over winter. However, if it is possible, going indoors and being able to regulate the temperature to be higher than Aeromonas Alley range can mitigate the likelihood of it being an issue.

Ulcer Disease Preparation

Prevention is ALWAYS better—and cheaper—than cure. Having said that, being prepared to quickly and effectively treat any symptoms that arise is a necessity. Having supplies and medications ready to do topical and injectable antibiotic treatments goes a long way in limiting any damage that the disease can cause.

Quarantining—Having a separate tank or “hospital pond” where the water temperature and parameters can be quickly and easily regulated is extremely helpful. Higher water temperatures (80-83ºF) can help to bump the koi’s immune system. It is also helpful in feeding correct amounts and creating an anti-bacterial bath.

Salt—Adding 3lbs/100gallons of salt can slow fluid and electrolyte loss from the ulcer. It can also help eliminate parasites (which could be one of the causes of the ulcers).

Chemicals—Hydrogen peroxide will clean out the wound. Some enthusiasts advocate the use of potassium permanganate or solutions of formalin/formaldehyde as well as Merthiolate or mercurochrome.

Medication—Putting a topical antibacterial ointment (like Neosporin or Polysporin) on the fish or bathing it in tricide-Neosporin mixture can help to combat and stop other forms of infection entering the koi, it but it won’t cure it. Injectable antibiotics (like Baytril)—injected behind the pectoral fin, just in front of the anal vent—have proven effective in curing ulcers.

It is worth noting here that there is a wide range of treatment styles and products that have been successfully adopted by koi enthusiasts. A professional opinion is a good first option to take.

Summer Conditions

The same standards that are used to keep koi hale and hearty during the warmest months of the year are the ones that will help to stave off Aeromonas in the Spring.

• Clean pond bottom,
• Clean filters,
• Proper water parameters,
• Quarantine all fish before adding them to the pond,
• Proper water changes.

Winter Prep

It may seem counterintuitive that your winter preparation can impact your spring, but it is true.

A fastidious winter prep will set your koi and pond up for a smoother transition into the spring.  A healthy immune system, even if it is slower in winter, means that your koi come out by and large with the same healthy immune system. It builds on itself, giving your koi a better fighting chance against Aeromonas (and other bacteria) as it becomes more active.

Here is a handy koi pond winter prep checklist.

Cleaning up the Alley

We have stressed more than once above, but it is worth repeating the steps to take to minimize the likelihood of Aeromonas getting a foothold in any of your koi come Spring.

• Cleanliness—this counts in winter when you are shutting up shop and in the spring when you open it back up. Clean filters (and low levels of organic waste) are key to success.
• Routine water changes—keeping the water fresh (and dechlorinated of course) can keep the bacteria in low concentrations as they start to go dormant.
• Oxygen levels—Oxygen deprivation can contribute to disease as well as provide an environment for bacteria to replicate.
• pH levels—crazy pH fluctuations will wreak havoc with an immune system. Between 7-9 and STABLE morning to night, is where you want your levels to be.
• New koi—don’t add any without rigorous quarantine, and especially not late in the season
• Diet—find the right balance of vitamins and minerals and use according to need.
• Don’t overfeed—feed recommended amounts and according to the water temperature schedule. With less decaying organics in the water, there is less for Aeromonas to thrive on.

Aeromonas and Aeromonas Alley are cause for some trepidation amongst koi owners but the bacteria can be controlled as can the overall health of your koi to lessen the chance of Aeromonas becoming an active pathogen.