Marine Oodinium

MARINE OODINIUM (Amyloodinium Ocellatum); Also occasionally known as Coral Fish Disease or Saltwater Velvet.

Although closely related to freshwater velvet (Piscinoodinium pillulare), these two external parasites differ in that the marine variety (Amyloodinium Ocellatum) does not have chloroplasts to produce nutrients (via chlorophyll and light), thus Marine Oodinium does not take on the appearance of Velvet. This difference is not always recognized in treatment recommendations on some prominent sites where this difference makes for different treatment methods as well. Ooodinium is also sometimes mistaken for Brooklynella, as symptoms and disease progression are similar. This species is found world-wide in tropical/temperate waters thus those of you having salt water fish have, or will, encounter this parasite, and why prevention is also important.

AMYLOODINIUM OCELLATUM BASICS:

Oodinium has been a fast moving killer in marine fish keeping for many years. Oodinium is a parasitic dinoflagellate which can infect and kill many species of saltwater fish. Similar to Crytptocaryon (Marine Ich and other external fish parasites, this Dinoflagellate is much more dangerous in the confines of an aquarium, especially a small overcrowded tank due to rapid re-infection.

Again, similar to Cryptocaryon, Oodinium there are 3 stages in its life-cycle: the infective Dinospore, which is free-swimming; the attached Trophont, which is found on external surfaces in contact with environmental water; and the mature cyst/ dividing Tomont. The mature cyst can release over 250 Dinospores which are free swimming and impossible to see with the naked eye. Since these Dinoflagellates do not have Chloroplasts like their freshwater cousins, they have to have a host to survive. Usually these Dinospores can only live 48 hours to one week without a host (this does not mean a tank free of a full blown infection for over a month is free of Oodinium as relatively healthy fish can be hosting them until ‘something goes wrong’).

The gills (similar to Brooklynella) are where Oodinium Dinospores attack first due to the soft tissue that is easy to pentetrate. The Dinospore attaches a filament into the host fish for feeding becoming a Trophont. After anywhere from 24 hours to a few days, the Trophonts cease feeding and form a Cyst to fall off a start a new cycle again. All stages possess a cellulose cell wall that can make them difficult to treat, however the Dinospore stage is the most susceptible to treatment (there are treatments for the other stages too, although less effective, I will discus them a little further down. Unlike Cryptocaryon and freshwater ich, the cell wall is not as thick and these parasites to not bury themselves nearly as deeply, which makes some treatments possible or more effective than with Cryptocaryon (the thinner cell wall also lends itself to more effective UV Sterilization too). The down side is that Oodinium often has a much faster life cycle and attacks the gills with much more furor than does Cryptocaryon or freshwater ich (Ichthyophthirius).

INDENTIFICATION:

A fish infected with Oodinium will exhibit abnormal behavior, which can include gasping, loss of color, gasping at the water surface, scratching on tank objects (flashing), constant swimming at the surface with spastic movements and trying to jump out, not eating, swimming with mouth open, being sluggish, and more. As the infection progresses, tiny white/opaque spots (trophonts) may be observed on the skin/fins as well as a mucous slime or coating, especially around the gill area.

TREATMENT:

There are no really good Oodinium treatments on the market in my opinion (Aquatronics used to make an excellent product called Marex which contained Chloroquine Phospate and pyrimethamine). Some have had success with Organi-Cure, but this is limited in my opinion. Metronidazole has shown some limited effectiveness for Oodinium (Metronidazole works reasonably well for Cryptocaryon). Probably the most effective current in tank treatment available is Copper Sulfate at .15 -.20 ppm (a copper test kit is a must!). Copper sulfate is not as effective in Marine Oodinium (as compared to freshwater velvet) in part due to the differences in the dinoflagellate (Marine Oodinium does NOT contain Chloroplasts).

Assuming you have done as much prevention as possible (or not) and still have an Oodinium outbreak, here are the steps I would recommend followed by steps to prevent further outbreaks and curtail the current outbreak (this is also assuming you have a display tank loaded with live rock and other organisms you would rather not see destroyed by the addition of copper):

[1] Remove the fish, all if possible.

[2] Prepare a freshwater dip; for this dip, I adjust pH (so as reduce more osmotic stress than need be) and add Methylene Blue (at double in tank strength), I will use a specific gravity of 1.001 for the saltwater fish. This dip should be no less than 3 minutes and no more than 5 minutes to be effective. This is very effective in removing Oodinium directly from the fish (including gills). Do not be alarmed if the fish ‘lays down’ and acts dead, this is a common initial reaction and the fish will usually perk up a minute or two into the dip. How this works is that the cell membrane of the Oodinium cyst cannot withstand the change in osmotic pressure as well as the fish and will burst, that is why the minimum three minutes is a must. I will also note that this dip is more effective for Oodinium than Cryptocaryon even though I recommend this for both due to the fact that the Oodinium Cyst does not imbed nearly as deep as the Cryptocaryon cyst does, allowing for a much more likely rupture of the cell membrane due to osmotic pressure.

[3] Even if you have to use sterile Rubbermade containers (or similar) with sponge filters for economic or space reasons (rather than hospital tanks) I highly recommend the purchase. Use these containers with at least TWO prepared with temperature adjusted pre-mixed saltwater. After each dip (minimum once per day is recommended), move the fish to a NEW hospital tank or container and dispose of the old water from the previous container. I recommend this procedure for 10-14 days. If possible still wait a full three weeks before returning to your display aquarium.

If you would rather not go through this process, treatment with copper sulfate for three weeks at .15 to .25 ppm in the display tank does still works (assuming you do not have any invertebrates or your remove them). Removing the copper with take copper removal resins and lots of water changes though (carbon will not work).

For very mild cases you cases you can try Metronidazole or Quick Cure (with an occasional dip thrown in if possible.

PREVENTION;

For me this is the most important aspect of this Oodinium, not getting and infestation in the first place.

Here are several practices that can help prevent this disease (the more of these procedures followed the better):

*Water parameters. This kind of goes without saying, however it is worth pointing out. No ammonia or nitrites, Nitrates under 20 ppm, Alkalinity over 240 ppm, Calcium 400- 450 ppm, Redox -300 mV.

*Baths or quarantine for new fish. I recommend quarantine or if not possible a 30 minute bath, for more details about baths or quarantine please read this article see the Full article link.

*UV Sterilization; This is one of the more important aspects for Oodinium prevention (although not the only and certainly not a cure all!). The key is a properly installed well made unit.

*A good source for your fish. This is important! Find a source you trust and stick with it, do not price shop unless you are sure of quality of the less expensive specimen. If your primary source for fish and other marine life has treated you well and sold you good stock, why shop around?

*Good Maintenance practices, Follow regular and efficient cleaning procedures.

*A good and balanced diet. Make sure your fish get what they need in their diet (each species is unique and a generic food is generally not enough unless you have a tank of damsels). For instance make sure your Emperor angel has sponge in its diet. One fish food I would strongly recommend as part of your basic diet for most marine fish (not the only food though) is Spirulina 20.

For my FULL article about saltwater Oodinium (much more information and pictures, please visit this URL: MARINE OODINIUM (Amyloodinium Ocellatum); Also occasionally known as Coral Fish Disease or Saltwater Velvet