Uncommon Saltwater Diseases and Infections

All saltwater aquarists will deal with common diseases in the beginning of their tank keeping journey. These include the infamous Ich, or “white spot disease,” skin and gill flukes, HLLE, Lymphocystis, velvet, and possibly even Brookynella, or “Clownfish Disease.” These each come with their own remedy, but the cures are well documented and easily available at any local fish store. Sometimes, we get a new fish who develops symptoms that don’t match these widely known ailments, and we are left to frantically research and hope to find someone else who has had the same issue and was able to cure it. This article is aimed at helping you identify these uncommon diseases and how to, hopefully, save your fish.

Uronema Marinum

Identifying this disease is fairly simple. It almost exclusively infects Chromis, although it may appear in other damsels and clownfish as well. Outside of these, it is incredibly rare to see Uronema on other species. It presents itself as a a red lesion or sore on the fish’s body. It is a free swimming parasite and requires no host, so the fish can never be returned to the infected tank, and all of the Chromis should be removed due to risk of infection. To treat the fish, remove him immediately as the disease spends incredibly fast. In a quarantine tank, treat his food with a binder and Metronidazole. Now, treat the quarantine tank with Metronidazole, acriflavine, chloroquine phosphate, or copper. If one does not seem to be working, switch to a different medication after using carbon to remove the old treatment. It can be tricky to cure once there is external damage.

Black Ich

This appears the same as normal ich, but with black spots instead of white. Black Ich is actually a
parasitic worm. Tangs in general seem to be the most susceptible to it. To treat, use a dewormer such as
praziquantel, or formalin if the worms are stubborn. Black Ich does not seem to be as life threatening as
actual ich (Cryptocaryon Irritans).

Gram Positive Bacteria

Within the broad category of bacterial infection, there are two categories of bacteria involved. Gram
positive bacteria are typically slower acting, and may not appear on the fish until it has been infected for
a period of time. These are most common in established individuals that may have been in your tank for
months, maybe even years. They can appear as a number of ailments, such as cloudy eyes, lack od
appetite, ripped fins, or lethargy. A lot of times, the immune system is able to fight the infection off on
its own. If you suspect that your fish has a gram positive infection, and does not seem to be great
distress, encouraging a healthy immune system is a good treatment route. To do this, feed a heavy,
varied diet and soak foods in vitamin supplements (not just garlic). Using a UV sterilizer, good water
parameters, and low stress levels will also all help. If, for whatever reason, you believe your fish cannot
fight it off naturally, treat him in a quarantine tank with kanamycin, Erythromycin, or another broad
spectrum antibiotic. If the fish stops eating for more than a day or is laying on the sand bed, it is time to
treat with medication.

Gram Negative Bacteria

This is the more dangerous type of bacterial infections. These are typically fast acting, and may kill fish
with 24 to 48 hours if left untreated. As opposed to gram positive bacteria infecting established fish,
gram negative is typically seen in newly acquired specimens. Red sores, bloody scales, white or dark
patches, and red streaks on fish are all phenotypic of these infections. These require immediate
treatment with Minocycline, Kanamycin, Metronidazole, and/or Nitrofurazone. The last three may be
combined at the same time for best results.

Internal Worms

In my experience, wrasses are the most susceptible to internal infection from worms. Many arrive at the
fish store already infected, so it is a good idea to treat these fish preventatively before adding to your
display tank. Symptoms include loss of appetite, color changes, irregular swimming patterns, white
feces, and the inability to gain or maintain weight. Treat the fish with medicated food for best results. I
have had good luck using a binding polymer such as Seachem Focus along with Metronidazole and

Tang Fingerprint Disease

This is a disease that we know little to nothing about, but is worth mentioning. Confined to tangs only,
this presents itself as a round or oval like areas of discoloration on both sides of the fish. It almost
always clears overnight and the fish appears as if nothing ever happened. It is thought to be viral in
nature, but this has yet to be confirmed. Nothing is typically required to cure this, although vitamin
enriched foods and perfect water quality are always encouraged, especially when things like this pop up.

Final Notes

Due to the large array of diseases we see in this hobby, and how much time and money we invest into
our tanks, we should all quarantine new animals before adding them into our display tank. Even
experienced hobbyists sometimes overlook this fact and add a fish directly into their tank, only to face
the repercussions days later. Some of these diseases can be incredibly difficult to identify, and it is not
worth risking infecting a whole tank that has been established for years just to save a couple weeks of
quarantine. Even after quarantining new fish, I highly recommend you keep certain medications and
extra 10 or 20 gallon setup on hand incase something pops up down the road, as some diseases can stay
dormant for quite some time. I always keep Erythromycin, Kanamycin, Metronidazole, and Praziquantel
medications on hand and they have saved me once or twice.

60 thoughts on “Uncommon Saltwater Diseases and Infections”

    1. Thirty-one years ago, I had a saltwater tank with everything I wanted, except one fish that I could not find. I cautiously added fish and invertibrates … used a quarantine tank … etc. After a year I gave up hope on finding that one fish, so I dismantled my quarntine tank. All the previous fish had been healthy and it seemed the quarantine tank was a waste of time. Then I found this missing fish, bought it and introduced it directly to my tank. Within two weeks, ever fish in my tank died. If you value you existing tank buddies, quarantine new fish.

  1. conner stumpf

    I unfortunately got marine velvet in on some snails I bought… wiped out all but my clown in days. Dont overlook any water or surface can transfer disease

  2. silvercityreefer

    The best thing I ever did was start a quarantine tank when I setup my first saltwater reef tank. This gives me time to observe new fish, ensure they are eating properly, along with treat any diseases that may arise prior to introducing them, and any diseases, to my main display.

  3. Glad you brought these conditions up, I hadn’t seen anything about a couple of them before now! Fortunately haven’t had any of these.

    Found a word error here above in the
    section Uronema marinum, fifth line
    To treat the fish, remove him immediately as the disease SPENDS should be /spreads
    incredibly fast.

  4. eddie roggero

    Great advice. Can you get those medications over the counter and what kind of shelf life do they have? Also do you quarantine inverts as well?

  5. Dwayne Newell

    Refugium information is outstanding. Wonderful ways to keep the Chaeto alive and thriving which in turn keeps my tank healthy.

  6. Kenneth Showman

    I learned my lesson about quarantining years ago with fresh water. Since then I quarantine everything (fish, coral, inverts). I don’t always keep my fish quarantine tank up and running, but I always keep some marine pure bio cubes, and some live rock in my sump incase I need to setup my quarantine tank on short notice. As always I love that you guys don’t just sell high quality products on your site, but also try and help educate us on the hobby.

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