Re:White swollen spot on horses tail!

Dear Ricky:

Thank you for the update, sir. I’m very sorry to hear that you weren’t able to save the seahorse with the tail infection, but it’s wonderful that his tankmates were unaffected and have even gone on to produce a brood of babies for you. Congratulations on your seahorse fry!

You’re quite correct — identifying the problem in its early stages and isolating the affected seahorse immediately for treatment is the best way to prevent an infection such as this from spreading to the rest of the herd. You did very well in that regard.

It’s very difficult to determine what the proximate cause of any specific health problem may have been from afar, but for what it’s worth, I would be happy to share my thoughts on the matter with you so that you can avoid tail infections (and bacterial infections, in general) in the future. Basically, anything that causes stress for the seahorses and suppresses their immune system can leave the seahorses vulnerable to disease problems such as bacterial infections (e.g., snout rot and tail rot; marine ulcer disease) or potential parasite problems.

This time of year, many health problems can be traced back to heat stress from summertime heat waves. If your tank had been running warmer than normal, or experienced a heat spike above 80°F, then heat stress may have played a role in your seahorse’s tail infection. (Tail rot in seahorses is often associated with heat stress.)

However, tail rot can also develop when a mechanical injury to the tail, such as a cut or scrape, becomes infected. The initial injury could be a nick from a hermit crab, a sting from an anemone or aggressive coral, irritation from an embedded bristleworm spicule or spicules, or simply an abrasion from a sharp edge on a rock or an overly abrasive piece of coral. Certain ciliates and protozoan parasites can attack the skin of seahorses, and when their integument is compromised, secondary bacterial and fungal infections may set in, resulting in tail rot. Likewise, subcutaneous emphysema (external GBD) can lead to secondary infections of the tail if untreated. Or an underlying bacterial infection (Vibrio, Pseudomonas or Mycobacterium) may be the primary cause of the tissue erosion and ulceration that’s so characteristic of tail rot.

So there are a great many other possibilities and stressors we should consider besides heat stress. With that in mind, I’m going to run through the factors that are most commonly associated with bacterial infections and then offer some suggestions on how to minimize such health problems in your aquarium, Ricky. (I’m sure most of these factors don’t apply in your case at all, but it never hurts to review them all for the sake of thoroughness.)

Disease-causing (pathogenic) bacteria are opportunistic invaders that are normally present in low numbers but don’t cause problems until the fish is injured, stressed, infested with parasites or otherwise weakened (Indiviglio, 2002). They will then take advantage of the overtaxed seahorse’s impaired immune system and reproduce extremely quickly, causing a variety of illnesses and problems (Basleer, 2000). Some of these are specific to seahorses, such as snout rot and white tail disease, and others are common to all fishes, such as Mycobacteriosis or popeye.

A bacterial infection almost always indicates that there is another problem that is stressing the fishes and weakening their immune response (Indiviglio, 2002). In addition to treating the infection itself, the hobbyist must also identify and correct the underlying problem in order to restore health. Check your water quality and aquarium parameters. A water change and general clean up are usually a good place to start.

One of the best ways to prevent bacterial infections and other disease problems is to provide them with a stress-free environment. Many of the parasites and pathogens that plague our pampered ponies are ubiquitous — present in low numbers in most everyone’s systems or within the seahorse’s body itself (Indiviglio, 2002). As a rule, healthy fish resist such microorganisms easily, and they only become a problem when seahorse’s immune system has been impaired, leaving it susceptible to disease (Indiviglio, 2002). Chronic low-level stress is one of the primary factors that suppresses the immune system and weakens the immune response, opening the way to infection and disease (Indiviglio, 2002). Long-term exposure to stressful conditions is very debilitating. Among other effects, it results in the build up of lactic acid and lowers the pH of the blood, which can have dire consequences for seahorses for reasons we’ll discuss later.

When disease breaks out in an established aquarium it is therefore generally an indication that something is amiss with your aquarium conditions. A gradual decline in water quality is often a precursor of disease (Indiviglio, 2002). Poor water quality is stressful to seahorses. Prolonged stress weakens their immune system. And an impaired immune system leaves the seahorse vulnerable to bacterial, parasitic, viral, and fungal infections to which healthy, unstressed seahorses are immune. As if that weren’t bad enough, there are a number of environmental diseases that are caused directly by water quality problems.

With this in mind, it’s important to review the most common stressors of captive seahorses. These include the design of the aquarium itself. A poorly designed seahorse setup that lacks adequate cover and shelter, or has too few hitching posts, will be stressful to the occupants (Topps, 1999). Seahorses are shy, secretive animals that rely on camouflage and the ability to conceal themselves for their safety and survival. A sparsely decorated tank that leaves them feeling vulnerable and exposed will be a source of constant stress (Topps, 1999). The seahorse setup should have plenty of secure hiding places so they can conceal themselves from view completely whenever they feel the need for privacy. It should be located in a low traffic area away from external sources of shock and vibration.

Needless to say, rapid fluctuations in temperature, pH, salinity and other aquarium parameters must also be avoided. A large aquarium of 40 gallons or more provides much greater stability in that regard than does a smaller setup. The greater the water volume in the aquarium and sump, the more stable the system will be.

Heat stress is especially debilitating and dangerous for seahorses due to a number of reasons (Olin Feuerbacher, pers. com.). For one thing, elevated temperatures can have a very detrimental effect on the immune system of fishes. This is because many of the enzymes and proteins involved in their immune response are extremely temperature sensitive (Olin Feuerbacher, pers. com.). Some of these protective enzymes can be denatured and inactivated by an increase of just a few degrees in water temperature (Olin Feuerbacher, pers. com.). So when seahorses are kept at temperatures above their comfort zone, their immune system is compromised and they are unable to fend off diseases they would normally shrug off.

At the same time heat stress is weakening the seahorse’s immune response, the elevated temperatures are increasing the growth rate of microbes and making disease organisms all the more deadly. Research indicates that temperature plays a major role in the regulation of virulence genes (Olin Feuerbacher, pers. com.). As the temperature increases, virulence genes are switched on, so microorganisms that are completely harmless at cooler temperatures suddenly become pathogenic once the water warms up past a certain point. Thus both the population and virulence of the pathogens are dramatically increased at higher temperatures (Olin Feuerbacher, pers. com.).

This is true of Columnaris and certain types of Vibrio. At cool temperatures these bacteria are relatively harmless, but at elevated temperatures they become highly contagious, virulent pathogens that kill quickly.

In short, it’s doubly important to keep seahorses at the proper temperature. Because of the reasons mentioned above and the fact that water holds less and less dissolved oxygen as it warms up, seahorses generally tolerate temps at the lower end of their preferred range much better than they handle temperatures at the upper limit of their range.

Incompatible tankmates are also stressful for seahorses. This includes not only aggressive, territorial fishes and potential predators but also inoffensive species that are restless, active fishes. Seahorses in an undersized aquarium may be uneasy around fishes that are always on the go, swimming tirelessly back and forth.

Other common stressors for seahorses include overcrowding, overfeeding, stray voltage, and a host of issues related to water quality: ammonia or nitrite spikes, high nitrate levels, inadequate circulation and oxygenation, high CO2 levels and low 02 levels, low pH, etc., etc., etc (Giwojna, Jun. 2002).

In short, if hobbyists provide their seahorses with a stress-free environment, optimum water quality, and a nutritious diet, they will thrive and your aquarium will flourish with a minimum of problems. As always, preventing disease in the first place is infinitely preferable to trying to treat health problems after the fact.

When disease breaks out in an established aquarium it is therefore generally an indication that something is amiss with your aquarium conditions. A gradual decline in water quality is often a precursor of disease (Indiviglio, 2002). Poor water quality is stressful to seahorses. Prolonged stress weakens their immune system. And, as we have been discussing, an impaired immune system leaves the seahorse vulnerable to bacterial, parasitic, viral, and fungal infections which healthy, unstressed seahorses easily fend off.

At the first sign of a health problem:

Because diseases are so often directly related to water quality, or due to stress resulting from a decline in water quality, when trouble arises the first thing you should do is to break out your test kits and check your water chemistry. Very often that will provide a clue to the problem. Make sure the aquarium temperature is within the acceptable range and check for ammonia and/or nitrite spikes first. See if your nitrate levels have risen to harmful levels and look for a drop in pH.

Be sure to check your dissolved oxygen (O2) level too. A significant drop in O2 levels (6 – 7 ppm is optimal) is very stressful yet easily corrected by increasing surface agitation and circulation to promote better oxygenation and gas exchange. At the other extreme, oxygen supersaturation is a red flag indicating a potentially deadly problem with gas embolisms (Gas Bubble Syndrome).

If any of your water quality parameters are off significantly, that may well be the cause of the problem or at least the source of the stress that weakened your seahorses and made them susceptible to disease. And correcting your water chemistry may well nip the problem in the bud, particularly if it is environmental, without the need for any further treatment.

Clean Up & Perform a Water Change

After a quick check of the water chemistry to assess the situation, it’s time to change water and clean up. In most cases, the surest way to improve your water quality and correct the water chemistry is to combine a 25%-50% water change with a thorough aquarium clean up. Siphon around the base of your rockwork and decorations, vacuum the top 1/2 inch of the sand or gravel, rinse or replace your prefilter, and administer a general system cleaning. The idea is to remove any accumulated excess organic material in the sand/gravel bed, top of the filter, or tank that could degrade your water quality, serve as a breeding ground for bacteria or a reservoir for disease, or otherwise be stressing your seahorses. [Note: when cleaning the filter and vacuuming the substrate, your goal is to remove excess organic wastes WITHOUT disturbing the balance of the nitrifying bacteria. Do not dismantle the entire filter, overhaul your entire filter system in one fell swoop, or clean your primary filtration system too zealously or you may impair your biological filtration.]

At first glance your aquarium parameters may look great, but there are some water quality issues that are difficult to detect with standard tests, such as a decrease in dissolved 02, transitory ammonia/nitrite spikes following a heavy feeding, pH drift, or the gradual accumulation of detritus. A water change and cleanup is a simple preventative measure that can help defuse those kinds of hidden factors before they become a problem and stress out your seahorses. These simple measures may restore your water quality and correct the source of the stress before your seahorse becomes seriously ill and requires treatment.

At any rate, Ricky, it sounds like you have done an excellent job of rehabilitating your seahorse tank following this disease outbreak and stemming the problem in the bud. A healthy interest in courtship and mating is always a good sign so it’s obvious that your seahorses find the conditions in your aquarium very much to their liking. Here’s hoping that they continue to thrive and prosper under your diligent care.

Respectfully,
Pete Giwojna