Once Marine velvet has broken out in a system all the susceptible fish will have the parasite and, even if they may have no signs, all the fish in that system will need treating. Otherwise, on re-introduction of the most susceptible species, the parasite will breakout again from the asymptomatic carrier fish that have remained in the main tank.
Treatments for marine velvet generally fall into three categories: chemical, environmental and experimental.
Probably because this disease is often misdiagnosed as something else, such as Brooklynella hostilis
or marine white spot, it hasn’t attracted a lot of grey literature cures unlike marine white spot. Although Vitamin C (ascorbic acid) therapy has been suggested as a “reef safe” cure, it is a bit of a long shot to say the least.
However, the following words of warning should be heeded before chemical treatment of a reef tank is attempted. (Source: Simon Garratt, posted on UltimateReef)
“Modern reef keeping methods have now moved way beyond the days when LR was considered a simple source of bacteria, and filtration. In modern systems the 'critter' population regularly feature as a major player in the functioning of the tank. As such, any treatment should consider the impact it will have on the tanks ecosystem.
'Reef safe' chemicals have often only been tested with the most commonly kept 'show' inverts. Many have not been tested nor claim to be safe with the multitude of background life that 'modern' reef keeping deems as beneficial, and form a substantial part of a modern reef eco-system, especially those containing sand beds etc. The use of 'chemicals' designed to kill parasites can have disastrous consequences in more diverse systems as they will kill off these beneficial animals as well as the parasite.
As a rule of thumb Keep chemicals out of the reeftank and carry out any treatments in a specialised quarantine tank. Whilst it’s perfectly acceptable and correct to deem the survival of the fish as a priority, it shouldn’t be at the detriment of the rest of the system, and certainly not to the degree it jeopardises the systems stability.”
Copper based treatments are easy to use and readily available from LFS in either ionic or chelated forms: chelated forms have a longer ˝ life in the aquarium, otherwise there is no difference between them because the active ingredient, copper ions, is the same. The two important things to remember about copper are that it will kill all invertebrates, and so cannot be used in a reef tank, and that you must get the dose right. If the dose is too low then the treatment will be ineffective, too high and you will poison your fish. I recommend that all copper treatments are carried out in a quarantine tank away from your invertebrates and that the levels of copper are monitored daily with a copper test kit to make sure the dose of copper falls into the therapeutic range of 0.2 to 0.3ppm for 7 to 10 days. Once a tank has been treated with copper it can be problematic reintroducing invertebrates because copper forms complexes with carbonates in the aquarium and these can leach back into the water with time causing copper toxicity to the invertebrates.
For this parasite, this isn’t the drug of choice. Being mostly plant it has much better copper detoxification methods than other protista that have more animal characteristics, such as Cryptocarion. So to cure this parasite you need to use longer exposure to copper in the range of 0.2 to 0.3ppm (10 to14 days) or higher copper doses. Data from the research community indicates that the median dose required to cure this parasite is 0.37ppm, however, this is getting close to the upper limit of copper toxicity for some of the more delicate fish species (circa 0.4ppm). Indeed, there is one report of a strain of Amyloodinium ocellatum requiring a dose of 1.2ppm to affect a cure.
b) Chloroquine diphosphate
Chloroquine diphosphate was reported by Noga & Levy (1995) as an effective and safe treatment for Amyloodinium ocellatum
. In this study a dose between 5 to10 mg/l cured the infection in ten days. However, this drug isn’t available in the UK from an LFS and has to be purchased (probably ordered) from a pharmacy. Although safe for fish it is very toxic to macro and micro algae and some invertebrates (in particular corals and anemones) so treatment should be done in a quarantine tank.
Cheap, cheerful and effective: sounds perfect, so what’s the catch? Well it’s toxic, carcinogenic and an irritant. It is, however, a uselful treatment for Amyloodinium ocellatum
. It can be purchased readily from your chemist and some off-the-shelf cures contain it or a related chemical (paraformaldehyde or gluteraldehyde) so a read of the labels or data sheets of some products is essential if you want to use it.
The best way to use this chemical is as a long term bath or to combine it with a freshwater dip (see environmental treatments).
For a long term bath, add 25ppm to your quarantine tank (it’s toxic to some invertebrates and algae, including most coralline algae species, so cannot be used in a reef situation) and this dose repeated every day for 10 days. Remember liquid formalin (which is how you will get it from the chemists) is 37 to 40% formaldehyde and you want 25ppm so you need to add 0.0625ml formalin per litre rather than 0.02ml to get the correct dose.
You can also use it as a short term dip in seawater at 200 to250ppm for 1 hour or combined with a freshwater dip at 200 to 250ppm for 3-5 minutes. For both dips the treatment regime should be carried out on days 1, 2, 3, 5, 7 & 11 followed by 4 to 6 weeks of observation in a quarantine tank.
NB formalin dips are a stressful process and are not advised for very delicate or very ill fish.
As this chemical is very toxic I would recommend that appropriate protective clothing is worn such as gloves and safety glasses and use it in a well ventilated place.
In my opinion to Acreflavin is one of the most under-used treatments available to marine fish keepers. It has a broad range of effect, being effective against protozoans, bacterial infections and external fungal diseases. It is as “reef safe” as any other “reef safe” treatment and is easily obtained. It can be bought in several formulations from the LFS but make sure it isn’t combined with malachite green or methylene blue which have toxicity issues in marine systems.
It is effective at a concentration of 6 ppm against Amyloodinium ocellatum
(Paperna, 1984) and this dose should be added to the aquarium on days 1, 2, 3, 5, 7, & 11. Your skimmer should be turned off and any activated charcoal removed. It dyes the water a greenish yellow colour which will change the light spectrum reaching your corals (if you decide to use it in a reef tank, personally I believe all medications are best kept out of a reef aquarium and used in a quarantine tank) and this colour is a bit of a pig to get rid of, but after treatment turning your skimmer back on and adding activated charcoal helps remove the coloration (as do water changes).
e) Hydrogen peroxide
More often used for crustacean ectoparasites, like sea lice, hydrogen peroxide can be very efficacious in treating Amyloodinium ocellatum
. It is administered as a bath of 100ppm hydrogen peroxide in seawater for 30 minutes. This treatment regime should be carried out on days 1, 2, 3, 7 & 11 followed by 4 to 6 weeks of observation in a quarantine tank.
NB Hydrogen peroxide dips are a stressful process and are not advised for very delicate or very ill fish.
Hyposalinty is often quoted as a good and safe way for treating Amyloodinium ocellatum
in a reef tank. Unfortunately Amyloodinium ocellatum
has a natural salinity range 3 to 45 ppt (Noga, 2000). The lower end of which has a SG of around 1.005, far to dilute to support marine fish and invertebrates. So if you DON’T want to cure your outbreak of marine velvet then by all means use hyposalinity therapy.
b) Freshwater dips
In freshwater the parasite drops off the skin of the fish very rapidly (leaving a small wound, which is important as we shall see later). Noga (2000) and Noga & Levy (1995) both reported that a single freshwater dip would remove 80-90% of the parasite. However, if the fish are simply returned to the tank where the outbreak occurred then they will just become re-infected. For this treatment to be effective then (like all the dip treatments discussed in this article) the fish should be kept in a quarantine tank and the main display tank kept fish free for 8 to 12 weeks. Once in the quarantine tank the treatment should be repeated on days 1, 2, 3, 5, 7 & 11 followed by 4 to 6 weeks of observation in a quarantine tank.
Remember those little wounds the parasite leave? Unfortunately, there can be thousands of them on an infected fish and those wounds can cause the fish to lose body fluids to the environment. This is exacerbated in freshwater so remember that a heavily infected fish could easily become physiologically stressed with this treatment method.
One of the most important things about a freshwater dip is that it will buy you some time to start another treatment or to set up a quarantine tank as even a very badly infected fish can lose most of its parasite in a few minutes and improve quite dramatically.
To carry out a freshwater dip:
- Take some freshwater (RO is best) and heat it up to the same temperature as the tank: I find the best thing is to float a plastic ice cream tub full of freshwater in the tank until the temperature equalises.
- Adjust the pH of the freshwater to match the tank using a commercial pH buffer.
- Catch the fish and pop it into the freshwater bath, watch the fish carefully and be prepared to remove it if it becomes very distressed. Normally 3 minutes in a freshwater bath will dislodge most parasites; this can be extended to five minutes. I would not leave the fish any longer than five minutes in a freshwater bath.
- Catch the fish and put it back into the tank. Do not pour the freshwater back in the tank as this may introduce the parasites back into the display tank.
NB A freshwater dip is a pretty stressful process and is not advisable for very delicate or very ill fish.
c) Low light & water changes
is a photosynthetic organism so a useful supporting strategy to any of these treatments is to keep the tank under a very low light regime just actincs or moonlight LEDS are perfect. It won’t cure the disease but can buy you some time until natural immunity takes over (see below) or you can set up a quarantine tank. If you also carry out 25% water changes each day you will also reduce the parasite load in the tank: again it won’t cure the disease but will buy you some time.
However, the low light will be detrimental to corals etc. But in the quarantine tank situation low light is very beneficial as it is not only detrimental to Amyloodinium ocellatum
but will help reduce the fish’s stress levels as well.
Having read this far you may think “damn, this is a tough disease and the remedies aren’t that effective, or difficult to use”, and to some extent you would be right. However, recent research on malaria (another protista which has some plant-like characteristics in its genome) suggests that some herbicides have tremendous potential for treating this pathogen. Again these treatments may be some way off and wouldn’t necessarily be suitable for a reef tank. However, they may, at last, provide a simple and effective way of controlling this pathogen.