Velvet dormant in tank for a year?

I found a study done on cryogenic preservation of Amyloodinium ocellatum.

Studies on the cryopreservation and in vitro culture of Amyloodinium ocellatum [2006]
Yang, Chu-Ya Cheng-Fang Chang [Corporate Author] Li-Lian Liu [Corporate Author] Shih-Chu Chen [Corporate Author] Jung-Pin Hsu [Corporate Author]

The Amyloodinium ocellatum was collected from cobia ( Rachycentron canadum ) gill and four tests including 4 ¢J storage, toxicity of cryoprotectant, cryopreservation and in vitro cultivation on fish cell line were conducted to establish the methods of preservation of Amyloodinium ocellatum. Survival of trophont, morphology and division of tomont and number of dinospore released were evaluated the effects of this study. The results showed that division irregulated, delayed and stopped of the tomont were found after stored at 4 ¢J over 48 hours. It was produced 1.08 x 10 4 cell/ml dinospores from 1 x 10 3 trophont at 4 ¢J, 24 hours storage group and significant higher ( p¡Õ0.0001 ) than other storage groups. For the toxicity of cryoprotectant, the concentration of DMSO 3~10¢M, Glycerol 3~10¢M, Methanol 3~10¢M, Ethanol 3~5¢M, PrOH 3~5¢M, DMAc 3~5¢M, Sucrose 3~15¢M, Trehalose 3~15¢M, Dextran 3~5¢Mand Ficoll 3~10¢Mwere safety to use on A. ocellatum trophont preservation. It was unsuccessful to cryopreserve the trophont of A. ocellatum when stored at direct liquid N2 freezing, different -20 ¢J freezing time, -1 ¢J min-1 freezing container and different cryoprotectant equilibration time contain 10¢MGlycerol and DMSO, respectively. Using the U-shaped tube of sigle and double loop could gain pure and bacteria-free dinospores. The results of in vitro cultivation of A. ocellatum showed that eel epidermis and cobia fin cell line with different culture mediums were unable to grow the trophont and tomont of A. ocellatum.

What I extract from this is that the frozen Amyloodinium stages were not viable after being unfrozen. This suggests that propagation via frozen food is highly unlikely.
 
Seems combining hyposalinity and copper treatment increases treatment success:

Amyloodiniosis in cultured Dicentrarchus labrax: parasitological and molecular diagnosis, and an improved treatment protocol

ABSTRACT: Amyloodinium ocellatum, the causative agent of amyloodiniosis (marine velvet, velvet disease), affects marine and brackish fish in various warm and temperate habitats. We recorded disease outbreaks with high morbidity and mortality rates in marine-cultured European seabass Dicentrarchus labrax fry at 2 locations in northwest Egypt. The sudden outbreak, high morbidity and mortality rates, and skin lesions with a velvety appearance in affected fish all indicated A. ocellatum infection. This was further confirmed by microscopic findings of the parasitic stage (trophonts) in skin and gill smears. While ecological factors including water temperature and salinity were all amenable to parasite establishment and propagation, mortality rates differed between the 2 farms, with rates of mortality well correlated with prevalence and intensity of A. ocellatum infections. Characterization by PCR targeting rDNA gene fragments and subsequent DNA sequencing and phylogenetic analysis further confirmed the molecular identity of the A. ocellatum isolate, which was genetically similar to isolates from other geographical locations. Finally, an improved treatment method using dual hyposalination and copper sulfate exposure to increase the efficiency and decrease the toxicity of copper sulfate was tested. The gradual reduction in water salinity coupled with copper sulfate treatment was more efficient at controlling the disease than only applying copper sulfate. To our knowledge, this is the first parasitological and molecular characterization of A. ocellatum in marine cultures in Egypt. The high molecular identity and close phylogenetic relationship further confirmed the monophyletic nature of A. ocellatum isolates.
 
I did find the article from Noga and reading the rest now...

BTW, have you been to a fish store within weeks before this started?
Any visitors who have tanks?
What about fish for eating? Bought any fresh fish from the grocery store and then worked on the tank?
Have you or anyone from your house been to the ocean or a brackish pond, river,...?
 
The signs do sound like velvet, but is there any chance we can verify it to make sure we are talking about velvet? Any possibility of lab tests?
 
The signs do sound like velvet, but is there any chance we can verify it to make sure we are talking about velvet? Any possibility of lab tests?
Lab tests are tricky and usually require to send in a living fish that is infected but not too severely so that it can survive shipping. But first you have to find a lab that can do the test and is accepting samples from hobbyists. Easier said than done.
The golden to rusty velvety shine at the right light and observation angles is usually definitive enough for us to call it and take the appropriate measures.
A microscopic or even genetic confirmation is mostly a concern if you want to publish a study about the parasite.

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I don't know of any lab around me that would analyze the fish. The remaining have been in therapeutic levels of copper for almost nine days now so I would hope it's no longer in the gills.

As to your other questions:
-Before this happened my last visit to my LFS was probably two to three weeks prior. I can't remember the exact date but I go about once a month for food and this started about two to two and a half weeks ago.
-No visitors that I can think of that have tanks.
-Haven't bought fresh seafood from the grocery store in over a month or two. I do use frozen cooked shrimp regularly but if it can't be viable in frozen fish food I'm hoping it's not in human food. The tank is at the opposite end of the house from the kitchen and 99% of the time I wash my hands before and after putting them in the tank (leaving myself a bit of wiggle room there in case of a time I forgot).
-No one in the house has been to the ocean or brackish water. I live on the east coast so it's winter here and we haven't traveled.
 
The timeline would fit for you to have brought it back from the fish store.

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I'm open to any possibility and due to the timeline it could have happened. But it's kind of a scary thought that a trip to your LFS to buy food could bring this to your tank. I didn't touch any water while there but of course touched handles to open the food freezer and counter to pay. I do browse around the tanks a bit to see what's there.

I'm a bit of a germaphobe so one of the first things I do when entering my house is wash my hands. Is there any other way to transmit? I've read about aerosol transmission but thought that was for tanks close together.
 
How far is the store from you in terms of traveling time?

Hands, if washed properly, should be a lesser issue.
Droplets transferred on clothes are also a possibility.
The biggest risks are shoes! That's why commercial aquaculture facilities and even some public aquaria have visitors and staff disinfect their shoes in food baths before entering sensitive areas.

These may give you an idea of how aquaculture facilities try to protect themselves from pathogens:
Biosecurity in Aquaculture
Biosecurity for Aquaculture Facilities
 
The store is about 5 miles away, so about 15-20 minutes.

I read the articles and would never have guessed shoes! Droplets on clothes I can see if you touch an area that's still wet and than place your hands in the tank.
 
20 minutes might be short enough for an Amyloodinium stage to remain viable and infective in a droplet.
A droplet can get onto you without even touching anything. All that's needed is a pump, an air stone, or anything else to create a splash or otherwise send a droplet airborne. And there is plenty of that in pretty much every fish store.
It has actually been published in research papers that tank to tank transmission of velvet is possible via airborne droplets. Though in those cases the tanks were in the same room.

A droplet transfer of velvet from a store to a home tank is still a long shot but so far it would be the most plausible explanation I could come up with given all the info you provided. Maybe try to find out if the store had issues with velvet when you were there before the outbreak. If they had an outbreak it would definitely support this theory.
 
At this point, I agree a droplet of water containing velvet is possible. I've been to the store since and they didn't have an outbreak. They do get shipments of new fish weekly that could have coincided with my visit before the outbreak. I'm there monthly so it's hard to remember specifics of a particular visit that was routine at the time.

I do appreciate your diligence on this. I have learned so much about velvet and pathogens in general. I'll never take anything for granted again.
 
I would still not be too concerned about going to the store. If this was indeed a droplet transfer from an infected LFS tank to your clothes and from there to your tank then it was a freak coincident - pretty much the equivalent to hitting the Powerball jackpot.

BTW, Amyloodinium is an algae and as such, it can live for a good while (weeks to months) of photosynthesis alone. But this also provides a way of keeping it in check by unleashing predators like rotifers, feather dusters, or sponges on it. This may not be too useful in a fish tank, but it may help to eliminate free stages in coral and invert quarantine systems.
 
Apologies for the delayed response. I agree this must have been a freak thing and I will continue to go to my LFS (would have rather hit the Powerball with the odds of it happening though).

I did not realize Amyloodinium was an algae, makes sense that it seems to like light.

I have read a few articles about rotifers, feather dusters and sponges since reading your post. It seems feather dusters should only be in a reef tank but I’m intrigued by the rotifers and sponges. Do you think they can flourish in a fish only tank? I have thought about keeping sponges before because of the angels I keep but never considered rotifers.
 
When speaking of feather duster worms in this context I'm thinking more of the tiny hard or soft tube ones that come as hitchhikers. Especially the hard tube ones prefer to to grow in the shade, on the back of the tank, in overflows, filter Chambers, and skimmers. Sometimes they can be a bit of a nuisance, but overall they are benign and actually beneficial.

The same goes pretty much for most sponges.

Rotifers on the other hand will be hard to maintain in any kind of reef tank - there are just too many things that like to eat them.

All those will of course only be able to survive and thrive in a tank without copper.

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