Theory on velvet

[Humblefish]

Disclaimer: What I’m writing about below is NOT scientific fact; Just a pet theory I thought up.

Most people think about “normal things” while in the shower; I think about fish disease stuff.

It’s always bothered me that Marine Velvet Disease seems so prevalent nowadays, without a clear reason why. Velvet has been around since I started out in this hobby, but I don’t remember it being the fast killer we see today. Even in tanks with unquarantined fish where copper wasn’t in use. Maybe it’s just lingering in the wholesalers’ tanks or the collection facilities before them, where the fish are long gone before symptoms arise. Or maybe something else is at least a contributing factor:

Reef grade lighting.

Velvet is different from other parasites, being it is a single celled dinoflagellate. This enables it to use photosynthesis as a means of obtaining nutrients (encysted tomonts and free swimming dinospores are both capable of doing this.) For example, velvet dinospores can remain infective for up to 15 days, whereas with ich theronts it’s only 48 hours. Photosynthesis enables the free swimmer to survive longer without finding a fish host to feed upon. This inevitably leads to a higher success rate of the parasite being able to locate a host (which is bad for the fish). Also, is it possible that light gives tomonts more energy to release additional dinospores in the first place?

Back in the day we used subdued lighting on most saltwater fish tanks, and the first “reef lights” were compact fluorescents and VHO bulbs. I’ve never had much success growing SPS or a clam under either of those. Nowadays we have LED lighting so strong that it will burn your corals if dialed up too high. Could this also be “fueling” velvet in a way unseen with past lighting options? The one big hole in my theory are metal halides, which have been around for at least 20 years (probably longer). Why didn’t we see a spike in velvet when reefers started using MH??

Please discuss below!!!

 

[EddieJ]

So your theory is that the increased lighting makes Velvet more of a deadly outbreak when introduced to display tanks correct? Reef lighting would not come into play from wholesalers and QT practices I would presume. So it seems more prolific these days due to diseased fish introduced to highly lit DTs cause many fatalities/infections.

Makes sense ..

 

[Gareth elliott]

Perhaps this could tie into the expansion of global trade in general and its effect on disease in general. As well as increased reporting due to the age of information.
A microbe that once was benign now the predominant strain showing increased lethality due to the speed of of its reproduction. Add the fact these strains can now go from one corner of the world to another in a day. And the use of common cures perhaps showing decreased efficacy due to the same process.

 

[rushbattle]

Now you are talking my language. In aquaculture the first step to treating amylo is to shut off/out the light(s). Culture systems are kept as dark as possible, and amylo is one of the reasons. I’d say you are on to something. I think it’s just industry knowledge because I haven’t seen it mentioned in any published papers. Probably because we do experiments on quarantined fish, or sterilized systems with newly hatched disease free*** fish.

 

[chipmunkofdoom2]

I think you're on to something.

The one big hole in my theory are metal halides, which have been around for at least 20 years (probably longer). Why didn’t we see a spike in velvet when reefers started using MH??

I don't know if this is necessarily a hole in your theory. I don't know a lot about wholesaling marine fish, but I would imagine that lighting a fish holding-tank with MH would be impractical for several reasons. First, the fish don't need the light. Second, MH tend to produce a lot of heat, and in a large industrial building, especially in California or other hot places where marine fish may make their way into the country, the added heat might be really difficult to deal with. Third is the cost. While not especially expensive, a quality MH setup will use a lot of power and cost money. With thin profit margins, simply the cost of running MH over a fish holding tank might be the reason it wasn't done.

LEDs have changed a lot though. Whether true or not, LEDs are seen as a long-term investment because they don't need bulb changes, use less energy, don't produce as much heat and are believed to last for a long time. I know that lots of coral aquaculture facilities are moving to LED-only lighting, probably for these reasons. I don't think it's far-fetched that a fish holding tank, a tank which never would have had a MH pendant over it 15 years ago or so, could now have a powerful LED light over it.

What we would really need is someone who had experience in the wholesaling business a decade or so ago and is still in the game now. Only this type of person would be able to tell us if this type of change has occurred.

 

[EddieJ]

Or it could simply seem more prevalent due to social media and sites like this one .. The connected world..

Very hard to quantify percentage of fish infected these days vs past days. Also this is now an instant gratification hobby ending in more and more mass infections/deaths ..

 

[Humblefish]

So your theory is that the increased lighting makes Velvet more of a deadly outbreak when introduced to display tanks correct?

Yes

Or it could simply seem more prevalent due to social media and sites like this one .. The connected world..

I’m basing this more on my own personal experiences (and my father’s as well). I’ve been in this hobby for almost 40 years now (didn’t QT for 30 of those years) and my dad was doing it at least 10 years before that (in Germany.) At one time we had almost 20 saltwater tanks inside the house, loaded with fish. Ich was always a constant problem, but it would come & go with rare casualties. But I can only remember a few times where we wiped out a DT from something “that looked like ich” but was probably velvet. Still just anecdotal I know, but I would think we would have experienced more frequent wipeouts if velvet was as prevelant back then. Or possibly had a secondary energy source which increased its potency.

 

[LJLKRL05]

Maybe it is a certain spectrum of light the LED's produce that increases the velvet life cycle.

 

[Humblefish]

Maybe it is a certain spectrum of light the LED's produce that increases the velvet life cycle.

Or a certain PAR...

 

[drawman]

I think it's a great thought. I would assume that velvet would be able to photosynthesize under almost any lighting, however. I think the closest corollary would be "brown" dinos that do well under most lighting.

I think wholesalers to LFS don't have the resources to rid their tanks of velvet which results in constant reinfection and spread. Maybe certain variants are becoming more communicable as well. Either way it's a nasty parasite!

 

[Big G]

So based on this theory, you could try leaving the lights off on your QT when introducing new fish. And leave them off until the prophylactic treatment of copper or CP is done. Or when emergency treatment is in action, leave off the lights, too. Perhaps by doing this it will give you an edge on this disease. I like it a lot. Will try this on a new group of fish next week.

 

[Halal Hotdog]

I think one other variable to consider is back in the day I don't recall a lot of people distinguishing between fish diseases. All white spots were ICH. One thing I do find 'ICH' on average seems to be less lethal vs 20 years ago. As we are distinguishing more between the parasites we are seeing velvet being a lot more lethal and ICH is something that can be maintained long term.

That being said, your theory about lights affecting dinoflagellate growth/replication rate seems very interesting. It makes sense to me and would love to see a study on it directly related to marine velvet.

 

[Josh Kraft]

I'd be interested in seeing the results of TTM / blacking out your TTM tanks / QT after. Maybe you could clear out velvet AND ich using no medication?

 

[Gareth elliott]

Being that the theory of protists deriving photosynthesis from bacteria and eventually leading to plants.
What pur do they use? Is it similar to corals or more like plants? In the ocean is velvet more common before 100 meters? Questions you now have me asking lol.

 

[drawman]

I'd be interested in seeing the results of TTM / blacking out your TTM tanks / QT after. Maybe you could clear out velvet AND ich using no medication?

The only issue with this is that velvet will still feed on the fish. He is saying that they can photosynthesize as an alternative during food (read fish) shortage.

 

[Big G]

Humble, do we know what percentage of photo vs. protein velvet needs to survive?

 

[Humblefish]

Humble, do we know what percentage of photo vs. protein velvet needs to survive?

I do not know that. Not sure if any studies have been done.

 

[melypr1985]

I would think that if the dinospores can get energy from light, that would increase the (i guess you could call it) productivity of the tomont stage. IE: it develops more of itself successfully to be released into the water. Not that it would create more individual free swimmers, but instead the free swimmers that are released are more viable than they might have been. My thoughts are a bit jumbled on this and I feel like I'm rambling here, but I was equating it with animals (or insects even) that have multiple babies or eggs..... say, of the free swimmers released, normally only 65% are viable and strong. Now, with the addition of the reef lighting, it's more like 86% are viable or even 90%. Which would explain the increase in speed that velvet seems to have taken on.

 

[Empress]

I have two 250 watt mh 20k's and one 400 watt 20k. I've been running them roughly 12 hours a day for years. Of course I change them every 12 months.

In the far corner of my tank I have a growing patch of cyano where the power heads can't reach. So I decided to turn down the photoperiod by 4 hours a day to help slow down the cyano. So now the halides are only on for 8 hrs a day. I started this about 3 weeks ago.

And guess what?? Daisy (my kole tang) looks smooth and shiny as I've ever seen her. She used to always have this fuzzy look to her. I did have velvet in my display a couple years ago. We went fallow for 6 weeks. The 3 mollies in my sump tell me that I don't have it anymore, but Daisy still had this "hazy" look about herself. I turned down the lights and now she looks great. Even my husband noticed it. I don't know what this all means exactly, but I like it. [emoji225]

 

[Gareth elliott]

So while playing with my moonlight settings i set uv to 3% and watched the fluorescence of my corals for a good 30 minutes.
Afterwards remembered this thread.

If velvet photosynthesizes and chlorophyll has a distinct fluorescence to other materials(animal proteins, rock etc.) could uv light be used as a diagnostic tool? Is the trophont fluorescent or just the dinospores? Is there enough glow of the dinospores to see against the reef? To follow the progression of a fallow period. If the trophonts have a distinctive glow compared to ich could uv be used to diagnose one vs the other?
Had read a paper on uv diagnostic of human scabies a little while ago so this came together for these questions.