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FAQs on: Nutritional Diseases

Thiaminase and its role in predatory pet fish (and other piscivores) nutrition

By Marco Lichtenberger

The seafood we offer to predatory pets like large fishes, axolotls and predatory turtles cannot always compete with their natural diet in terms of variation and freshness.

Because we mostly feed our pets frozen foods, we need to consider any biochemical differences between their natural diet and their captive diet. The freezing and thawing processes can result in deficiency diseases in the long run, and if this is exacerbated by poorly chosen food items, the result is that our pets will enjoy a shortened lifespan.

In particular, one problem often discussed in the context of feeding predatory animals is the presence of the enzyme thiaminase in many types of fish and invertebrates. While strong and often controversial opinions on this topic have been voiced among pet owners, there is a distinct lack of solid information. It is the intention of this article to summarize what is known about thiaminase and the related deficiency disease, which can be relevant for pet fish nutrition.

"Predatory fishes like this moray eel need a fishy diet, but not all foods available in trade are equally safe with regard to their thiaminase content."

What is thiaminase?

Thiaminase is an enzyme, a chemical compound that destroys or inactivates thiamine. Thiamine is an important vitamin also known as Vitamin B1. There is not just one type of thiaminase, but several different ones, some of which can be produced by bacteria, fungi, plants and potentially animals.

The lack of Vitamin B1 in humans is called beriberi.

Thiamine Deficiency Syndrome and its symptoms

Vitamin B1 (also known as thiamine, thiamine hydrochloride, and in older text books, as aneurine hydrochloride) is an essential nutrient for most animals. It is a colorless and water soluble chemical that helps to convert carbohydrates into glucose. It is particularly important for the correct functioning of the nervous system. A lack of Vitamin B1 is called a Thiamine Deficiency Syndrome.

Symptoms of this syndrome are well known from several commercially important fish groups and can be confirmed using appropriate biochemical tests. Flatfish fed exclusively with thiaminase-rich clams suffer and die from paralysis and related physical shocks. Eels show a trunk-winding syndrome and hemorrhages along the base of the fins (similar symptoms have been reported from moray husbandry, too). Salmonids show nervous disorders, poor appetite, poor growth and jumpiness (again, similar things have observed among a variety of ornamental fish species). Skin congestion and haemorrhage have been reported from carp and other cyprinids. In general then, excessive amounts of thiaminase are connected with symptoms of sickness that include poor growth, loss of appetite, abdominal swelling and hemorrhage, loss of equilibrum, convulsions, muscle atrophy and a weak immune system.

While it has not yet been scientifically proven that pet fish suffering from the above mentioned symptoms have Thiamine Deficiency Syndrome, the parallels with their food fish relatives are striking. The problems of thiaminase are now well known in the professional fields of animal nutrition (e.g. fish farms), but so far this information has not been widely taken up by aquarists and pet owners. But it is clear that those hobbyists keeping large predatory fish and other carnivorous animals need to be familiar with the problem of Thiamine Deficiency Syndrome, and use that information to make sensible choices when selecting food for their livestock.

Aren't thiaminase containing fish eaten in the wild?

Yes, they are, and this can cause predatory fish massive problems. The offspring of salmon from the Baltic Sea -- which apparently feed mostly on thiaminase-rich herring and relatively little food that contains high levels of Vitamin B1 -- were found to suffer from a condition called Reproduction Disorder M74. This was later identified as being simply one particular form of Thiamine Deficiency Syndrome. The eggs produced by adult salmon were provided with very little thiamin, and the fry that emerged almost all died soon after hatching. Comparable problems have been found among salmonids in the Great Lakes of North America, and this has been hypothesized to be related to a diet containing a large proportion of alewives, another type of thiaminase-rich fish.

However, most of the time predatory fishes maintain a kind of balance between those prey fish rich in thiaminase and those fish rich in Vitamin B1. As long as the predator has a reasonably varied diet, it should get enough Vitamin B1 to stay healthy. It should be mentioned that in the examples of the sick salmonids from the Baltic, the key problem was that they were not eating a varied diet, but mostly consuming just one type of prey.

The big problem for captive fish is that they are fed frozen fish. Thiaminase is not destroyed by freezing, and over time will break down whatever Vitamin B1 is present in the frozen fish. The longer the fish is stored, the less Vitamin B1 it will contain. Furthermore, any fish fed such frozen fish will be consuming the thiaminase, and that will destroy some of the Vitamin B1 it already has. Making things even worse, freezing and thawing both break down some of the Vitamin B1 content of food as well.

While freezing does not destroy thiaminase, heating it will. This is why cooked fish is not dangerous with regard to thiaminase for human or animal nutrition. From the perspective of a fishkeeper, the big drawback to cooking food is that heating destroys a lot of the useful nutrients as well. While omnivorous humans compensate for that by eating a varied diet containing both raw and cooked plant and animal foods, piscivorous fish have no such option. They cannot be fed cooked fish and expected to stay healthy.

At least some types of live feeder fish will contain more Vitamin B1 than frozen foods, but the downside here is that the convenience of live foods is accompanied by a major risk of introducing pathogenic microorganisms such as mycobacteria and endoparasites. Feeder fish are also expensive compared with frozen foods, and as will be described shortly, many of the types of feeder fish widely sold contain a great deal of thiaminase anyway, dramatically reducing their usefulness.

Which fish and other food of aquatic origin contains thiaminase?

A common generalisation often made by aquarists is that marine fish don't contain much thiaminase while freshwater fish do. This is not the case at all.

From my review of the literature, of the 32 species of freshwater fish tested, 18 of them were found to contain thiaminase. Among the 61 marine fish tested, 32 were found to contain thiaminase. In other words, 56% of the freshwater fish examined contained thiaminase compared with 51% of the marine fish species. If there is a difference between freshwater fish and marine fish in terms of thiaminase content, any such difference appears to be rather small.

Among the food fish families consumed by man, species that contain thiaminase include minnows, carps, herrings, anchovies, goatfishes and snappers. Many different invertebrates have also been found to contain thiaminase, including mussels, clams and shrimps/prawns such as those in the genus Penaeus, sometimes in even higher concentrations than those found in fish.
In contrast several groups of fish have been generally found to be free of thiaminase, including North American sunfishes, flounders, cods and croakers.

"Bivalves such as clams can are a good food within a varied diet, but many contain a lot of thiaminase and
should not be used exclusively; some however, notably cockles, contain little thiaminase and are consequently a better all-around food for mollusk-feeding predators such as pufferfish."

Thiaminase content review

The data on thiaminase content comes from various sources, mostly from the National research council (1982), Deutsch & Hasler (1943), Greig & Gnaedinger (1971) and Hilker & Peter (1966); see also the literature list at the end of the article. The lists are far from complete, but most of the usually marketed and so far examined species are enlisted. Although primarily based on coldwater food fish and invertebrates, thiaminase content information exists for several tropical species widely marketed, and these been included accordingly.
Species that contain thiaminase

Freshwater fish
Family Cyprinidae (Minnows or carps):
Common bream (Abramis brama)
Central stoneroller (Campostoma anomalum)
Goldfish (Carassius auratus)
Common carp (Cyprinus carpio)
Emerald shiner (Notropis atherinoides)
Spottail shiner (Notropis hudsonius)
Rosy red, Fathead minnow (Pimephales promelas)
Olive barb (Puntius sarana)

Family Salmonidae (Salmonids):
Lake whitefish (Coregonus clupeaformis)
Round whitefish (Prosopium cylindraceum)

Family Catostomidae (Suckers):
White sucker (Catostomus commersonii)
Bigmouth buffalo (Ictiobus cyprinellus

Family Ictaluridae (North American freshwater catfishes):
Brown bullhead catfish (Ameiurus nebulosus)
Channel catfish (Ictalurus punctatus)

Other families:
Bowfin (Amia calva) - family Amiidae (Bowfins)
Burbot (Lota lota) - family Lotidae (Hakes and burbots)
White bass (Morone chrysops) - family Moronidae (Temperate basses)
Rainbow smelt (Osmerus mordax) - family Osmeridae (Smelts)
Loach, Weatherfish (Misgurnus sp.) - family Cobitidae (Loaches)

Brackish (freshwater to marine) fish

Family Clupeidae (Herrings):
Alewife (Alosa pseudoharengus)
Gizzard Shad (Dorosoma cepedianum)

Other families:
Sea lamprey (Petromyzon marinus) - family Petromyzontidae (Lampreys)
Fourhorn Sculpin (Triglopsis quadricornis) - family Cottidae (Sculpins)
Salmon (sp. indet., processed and salted, probably Oncorhynchus sp.) - family Salmonidae (Salmonids)

Marine fish

Family Engraulidae (Anchovies):
Broad-striped anchovy (Anchoa hepsetus
Californian anchovy (Engraulis mordax)
Goldspotted grenadier anchovy (Coilia dussumieri)

Family Clupeidae (Herrings):
Atlantic herring (Clupea harrengus)
Atlantik menhaden (Brevoortia tyrannus)
Gulf menhaden (Brevoortia patronus)
Razor belly sardine (Harengula jaguana)
Sauger (Harengula jaguana)

Family Scombridae (Mackerels, tunas, bonitos):
Chub mackerel (Scomber japonicus)
Skipjack tuna (Katsuwonus pelamis)
Yellowfin tuna (Neothunnus macropterus)

Family Lutjanidae (Snappers):
Green jobfish (Aprion virescens)
Ruby snapper (Etelis carbunculus)
Crimson jobfish (Pristipomoides filamentosus)

Family Carangidae (Jacks):
Giant trevally (Caranx ignobilis)
Doublespotted queenfish (Scomberoides lysan)
Bigeye scad  (Selar crumenophthalmus)

Family Mullidae (Goatfishes):
Red Sea goatfish (Mulloidichthys auriflamma)
Yellowstripe goatfish (Mulloidichthys samoensis)
Manybar goatfish (Parupeneus multifasciatus)

Other families:
American butterfish (Peprilus triacanthus) - family Stromateidae (Butterfishes)
Southern ocellated moray (Gymnothorax ocellatus) - family Muraenidae (Moray eels)
Bonefish (Albula vulpes) - family Albulidae (Bonefishes)
Milkfish (Chanos chanos) - family Chanidae (Milkfish)
Common dolphinfish (Coryphaena hippurus) - family Coryphaenidae (Dolphinfishes)
Hawaiian flagtail (Kuhlia sandvicensis) - family Kuhliidae (Aholeholes)
Black cod (sp. indet.) - family Moridae (Morid cods)
Flathead mullet (Mugil cephalus) - family Mugilidae (Mullets)
Sixfinger threadfin (Polydactylus sexfilis) - family Polynemidae (Threadfins)
Regal parrot (Scarus dubius) - family Scaridae (Parrotfishes)
Swordfish (Xiphias gladius) - family Xiphiidae (Swordfish)


Ocean quahog (Artica islandica)
Clam (Tellina spp.)
Cherrystone, Chowder, Steamer clams (family Veneridae)
Pigtoe mussel (Pleurobema cordatum)
Scallop (Pecten grandis)
Hawaiian clam (sp. indet.; extremely high in thiaminase)
Blue mussel (Mytilus galloprovincialis)

Limpet (Helcioniscus sp.)

Hawaiian flying squid (Nototodarus hawaiiensis)

Prawn, Tiger shrimp (Penaeus spp.)

"The flesh of this Brazilian ocellated moray Gymnothorax ocellatus contains thiaminase. Makes a better pet fish than food fish, anyway!"

Species that do not contain thiaminaseFreshwater fish

Family Centrarchidae (North American Sunfishes):
Largemouth bass (Micropterus salmoides)
Northern rock bass (Ambloplites rupestris)
Northern smallmouth bass (Micropterus dolomieu)
Blue gill (Lepomis macrochirus)
Black crappie (Pomoxis nigromaculatus)
Pumpkinseed (Lepomis gibbosus)

Family Percidae (Perches):
Yellow perch (Perca flavescens)
Walleye (Sander vitreus)

Family Salmonidae (Salmonids):
Bloater (Coregonus hoyi)
Lake trout (Salvelinus namaycush)
Rainbow trout (Oncorhynchus mykiss)

Other families:
Ayu (Plecoglossus altivelis) - family Plecoglossidae (Ayu fish)
Longnose gar (Lepisosteus osseus) - family Lepisosteidae (Gars)
Northern Pike (Esox lucius) - family Esocidae (Pikes)

Brackish (freshwater to marine) fish
Family Salmonidae (Salmonids):
Cisco, Lake herring (Coregonus artedi)
Atlantic Salmon (Salmo salar)
Coho salmon (Oncorhynchus kisutch)
Sea trout (Salmo trutta)

Other families:
Common eel (Anguilla anguilla) - family Anguillidae (True eels)
Pond smelt (Hypomesus olidus) - family Osmeridae (Smelts)

Marine fish
Family Pleuronectidae (Righteye flounders):
Winter flounder (Pseudopleuronectes americanus)
Winter flounder, Lemon sole (Pseudopleuronectes americanus)
American plaice (Hippoglossoides platessoides)
Yellowtail flounder (Limanda ferruginea)
Atlantic halibut (Hippoglossus hippoglossus)
European plaice (Pleuronectes platessa)

Family Gadidae (Cods and haddocks)
Atlantic cod (Gadus morhua)
Haddock (Melanogrammus aeglefinus)
Saithe, Pollock (Pollachius spp.)

Family Sciaenidae (Drums or croakers):
Atlantic croaker (Micropogonias undulates)
Southern kingfish (Menticirrhus americanus)
Spot croaker (Leiostomus xanthurus)
Silver seatrout (Cynoscion nothus)
Sand weakfish (Cynoscion arenarius)

Family Carangidae (Jacks):
Greater amberjack (Seriola dumerilii
Yellowtail scad (Atule mate)
Mackerel scad (Decapterus pinnulatus)

Family Labridae (Wrasses):
Cunner (Tautogolabrus adspersus
Tautog (Tautoga onitis)

Family Scombridae (Mackerels, tunas, bonitos):
Atlantic mackerel (Scomber scombrus)
Kawakawa  (Euthynnus affinis)

Other families:
Tusk (Brosme brosme) - family Lotidae (Hakes and burbots)
Largehead hairtail (Trichiurus lepturus) - family Trichiuridae (Cutlassfishes)
Piked dogfish (Squalus acanthias) - family Squalidae (Dogfish sharks)
Hake (Urophycis spp.) - family Phycidae (Phycid hakes)
Inshore lizardfish (Synodus foetens) - family Synodontidae (Lizardfishes)
Mullet (Mugil spp.) - family Mugilidae (Mullets)
Scup, Southern porgy (Stenotomus chrysops) - family Sparidae (Porgies)
Ocean perch, redfish (Sebastes marinus) - family Sebastidae (Rockfishes)
Black seabass (Centropristis striata) - family Serranidae (Sea basses and Groupers)
Hardhead sea catfish (Ariopsis felis) - family Ariidae (Sea catfishes)
Searobin (Prionotus spp.) - family Triglidae (Searobins)
Silver hake (Merluccius bilinearis) - family Merlucciidae (Merluccid hakes)
Eyestripe surgeonfish (Acanthurus dussumieri) - family Acanthuridae (Surgeonfishes)
Atlantic blue marlin (Makaira nigricans) - family Istiophoridae (Billfishes)
Blotcheye soldierfish (Myripristis berndti) - family Holocentridae (Squirrelfishes, soldierfishes)
Glasseye (Heteropriacanthus cruentatus) - family Priacanthidae (Bigeyes or catalufas)
Great barracuda (Sphyraena barracuda) - family Sphyraenidae (Barracudas)
Cockle (Cardium spp.)

Marine shrimps (sp. indet.; Hawaii)
Portuguese crabs (sp. indet.)

Brief squid, calmar (Lolliguncula brevis)

"All so far examined flatfish like this European plaice (Pleuronectes platess) are free of thiaminase."

"So far examined fishes from the family Gadidae like this Pollock (Pollachius pollachius) are free of thiaminase and a good choice for pet fish nutrition."

What to do with fishes not mentioned in the lists above?

Certainly not every fishy food is included in the lists above. For many food items probably no data exists, yet. What you can do if you are missing a food fish in the list is:
1. Find out the scientific name of the food fish and compare it to the list again. Many fish are traded under obscure names.
2. Try checking literature for the food species yourself. Search engines are your friends. (If you are successful, reporting it back could help other hobbyists).
3. If you fail to find information, treat the fish in question as if it contained thiaminase.

What obviously won’t always work is to see if the fish in question belongs to the same genus or family as one or more of the fish enlisted (e.g. with Related fish from the same genus or family may have a similar composition in terms of protein or fat, but the thiaminase content sometimes seems to vary greatly even between species within a single genus, and may even vary from population to population.

Little or nothing is known about the thiaminase content of some of the small ornamental fishes usually used as feeders. However, goldfish and minnows (including rosy red minnows) definitely contain thiaminase and consequently make very poor choices as feeders. On the other hand, the Poeciliidae (e.g., guppies, mollies, mosquitofish) are often recommended as safe feeder fishes for predators because of their presumed to be low thiaminase content. Despite claims among aquarists that guppies contain thiaminase producing bacteria, I am not aware of any scientific study demonstrating this to be the case. Since poecilids are grazers, an uptake of thiaminase-producing cyanobacteria would be possible, though less probable in a freshwater aquarium where a much smaller variety of algae are likely to be present than in the wild.

Anecdotal evidence that the notoriously delicate Ribbon Eel can live on a diet of mostly gut loaded black mollies for more than 15 years would seem to suggest that poeciliids are largely thiaminase-free and make a safe choices for feeder fish. Of course this depends on the quality of the feeder fish being used, and cheap feeder guppies from pet stores might not contain any thiaminase but could certainly contain all sorts of pathogenic bacteria and parasites! So when poeciliids are described as being among the best feeder fish, this depends on them being bred at home and gut loaded with Vitamin B1-enriched foods, such as a good quality flake food. Because poeciliids have a high tolerance for saltwater (mollies in particular can be maintained indefinitely under marine conditions) they are equally useful in saltwater tanks as in freshwater aquaria. But this said, avoidance of feeders is the best option in terms of cost, convenience and safety, and the use of feeders should be limited to those few obligate piscivores that will not take dead food or for the acclimation of newly introduced livestock prior to being trained to accept dead or frozen foods.

“The thiaminase content of guppies is unknown, but considered low or negligible, making them much safer to use than goldfish or minnow feeders.”

How can I avoid the thiamine deficiency syndrome?

Prevention is the best way to “treat” the thiamine deficiency syndrome. Things to avoid include:
1. Restrict feeding thiaminase containing fish to no more than 20% of all meals.
2. Avoid feeding exclusively frozen bivalves or shrimps, because these potentially have very high thiaminase content.
3. Avoid fish that was frozen for long periods (several months).

Things to do:
1. Keep the diet generally as varied as possible! Remember, nutritional shortcomings in one type of food will be cancelled out by the other types of food, so the more types of food, the smaller the chance of nutrient imbalances.
2. Soak food in a vitamin product intended for pet fish prior to feeding at least once a week, more often when feeding lots of shrimps and bivalves!
3. Get small packages of food, and use them up quickly.

Final words

Thiaminase-containing food will not be instantly lethal to your pets, but over the long term can result in a slow decline in health. Simple measures and a little conscientiousness when buying and preparing food is all that is needed to easily avoid Thiamine Deficiency Syndrome.


Anglesea, J.D. & Jackson, A.J. (1985): Thiaminase activity in fish silage and moist fish feed. Anim. Feed Sci. Tech. 13: 39-46.
Deutsch, H.F. & Hasler, A.D. (1943): Distribution of a Vitamin B1 destructive enzyme in fish.- Proc. Soc. Exp. Biol. Med. 53: 63-65.
Food and agriculture organization of the United Nations (1980): ADCP/REP/80/11 - Fish Feed Technology.  HYPERLINK "http:]" http:]
Greig, R.A. & Gnaedinger, R.H. (1971): Occurrence of thiaminase in some common aquatic animals of the United States and Canada. Special Scientific Report—Fish. U.S. Dept. Commer. Natl. Mar. Fish. Serv. 631: 1-7.
Hilker, D.M. & Peter, O.F. (1966): Anti-thiamine activity in Hawaii fish.- J. Nutr. 89(4):419-421.
National Research Council (1981): Nutrient Requirements of Cold-water Fishes. Washington, D.C.: National Academy Press.
National Research Council (1982): Nutrient Requirements of Mink and Foxes, Washington, D.C.: National Academy Press.
National Research Council (1983): Nutrient Requirements of Warm-water Fishes and Shellfishes. Washington, D.C.: National Academy Press.
National Research Council (1993): Nutrient Requirements of Fish. National Academy Press. Washington DC, USA.
Royes, J.-A.B. & Chapman F.A.: Preparing your own fish feeds.- University of Florida, 9 p.  HYPERLINK "http:]" http:]
Scardi, V. & Magri, E. (1957): Thiaminase activity in Mytilus galloprovincialis.- Boll Soc Ital Biol Sper. 33(7):1087-1089 (in Italian).
Wistbacka, S.; Heinonen, A.; Bylund, G. (2002): Thiaminase activity of gastrointestinal contents of salmon and herring from the Baltic Sea.- Journal of Fish Biology 60(4), 1031-1042.
Yudkin, W.H. (1949): Thiaminase, the Chastek-paralysis factor.- Physiol. Rev. 29: 389-402.

Thiaminase    1/4/12
Hello and Happy New
Year to the Wet Web Crew,
 <Hi Richard and a happy new year to you, too.>
I've been doing research on Thiaminase in fish as it relates to feeder fish and in so doing have contacted a number of fish nutritionist and the author of a study on Thiaminase in Lake Trout.  Here are some interesting facts:
1) Amazingly, there are no known examples of warm water species of fish or reptiles suffering from thiamin deficiency when consuming live prey.  No references period.
<No scientific references maybe, since there is little interest in this topic so far. There is also no scientific study showing that consuming live, Thiaminase containing food has no impact on warm water fishes. What we have is empirical evidence from decades of keeping predatory fishes (including some mostly fed with feeders, although is is done not that often and with a lot of species), which can be linked to malnutrition and at least symptoms similar of those suffering from a lack of thiamin, just have a look on the disease FAQs of the common predatory fishes at WWM.>
Thiaminase became a concern after it was discovered that fish in the Great Lakes and Baltic suffered low fertility rates as a result of consuming non-native species of Thiaminase containing fish.  This phenomena is strictly limited to these studies and it is postulated that it is temperature related and associated with the amount of time prey is in the stomach prior to digestion.  Thiamin is released upon destruction of tissue and will begin to degrade thiamin in the gut. In warm-water species enough thiamin is absorbed in the gut prior to its deactivation to make it a non-factor.
<If this was that simple no animal with a fast metabolism would suffer from eating Thiaminase rich food, but they do, even mammals with much faster metabolisms than warm water fishes.>
Fish that contain Thiaminase are often actually rich sources of B1. It is the digestion rate that effects uptake of B1 in lake trout which is why you see higher thiamin content in Lake Trout in the summer months even though the Thiaminase levels in alewives are at their highest.
 2) Feeding an exclusive diet of frozen fish that contain Thiaminase over many months will be the surest way to produce B1deficiency.
<That's actually what can be observed most often in the hobby.>
This has been demonstrated with mink, foxes and alligators.  All of which were fed frozen Thiaminase containing fish and after a number of months developed beriberi.  However, if someone had to feed frozen, simply using a varied diet of multiple species of fish that included non-Thiaminase species would prevent malnutrition.
<Just what is recommended in the WWM article.>
The mink and fox farmers learned to cook their fish soon after landing to neutralize Thiaminase.  Ice crystals rupture cell structures that then releases Thiaminase into the tissue.  Even in a freezer Thiaminase will deactivate thiamin rather quickly.
 3) Thiaminase does not cross the blood barrier but remains in the gut.
 Some species of fish appear to sequester Thiaminase in special cell vacuoles, but with predatory fish the Thiaminase does not cross the blood barrier and remains in the gut. Thiaminase passes out of the gut with the undigested food.  Thiaminase does not build up in the system and as long as a varied diet is followed that includes non-Thiaminase containing species fed at different times, even cold-water species will thrive. There is no science or evidence that feeding live has ever caused thiamin deficiency in warm-water species. The fish nutritionist that I have contacted, the author of the Lake Trout study and all the literature concur on this point.  Only feeding an exclusive diet of frozen Thiaminase containing fish will cause vitamin B1 deficiency in
warm-water species. And, only if continued for prolonged periods of time.
Your discussion on Thiaminase is extensive and mostly accurate, but I do not believe that it takes these subtleties into mind, which leads to consequential conclusions on the part of the reader.
<We'll add your opinion to the FAQ.>
It is important to emphasize that this is a cold-water disease as defined by the literature, and that there is a monumental difference between feeding live vs. frozen in regards to nutritional quality in many respects.
<See my opinion above.>
Thank you for your time.
<Welcome. Marco.>
Sincerely,  Richard Rombold
Re: Thiaminase    1/5/12

Let me say first, you guys rock that you take this issue so seriously. 
<Thanks for your kind words. My intention was seeing predatory aquarium fish suffering from symptoms known from thiamin deficiency for many years.
Those belong to two groups: A big group being fed frozen food (mostly one type of fish or shrimp or bivalve) and a small group being fed goldfish and minnow feeders. I am not aware of apparently Thiaminase related problems with feeder mollies (as noted in the article), though.>
Let me try to review this article and put some thought into your good points and get back to you in a couple of days.
I greatly suspect that the Barramundi were not fed live fish.
<That's probably right. My point in sending this article citation was mostly to show a scientific study, which in addition to empirical evidence, states if Thiaminase can be a problem for tropical fish, since you suggested their faster metabolism and faster uptake of thiamin would prevent them from the consequences. Based on the cited article and empirical evidence I cannot confirm the idea of a fast metabolism making Thiaminase completely harmless in tropical fishes, and it seems it cannot be confirmed for reptiles and mammals. The digestion period of small to medium sized morays for example is between 24-72 hours depending on the food composition and the activity and size of the fish (much slower than in a mink, which can show Thiaminase related diseases). Inside a tropical fish or warm blooded animal the breakdown of thiamin by Thiaminase can be faster than inside a cold water fish.
With regard to feeding live or fresh fish, I do concur that the relation of thiamin to Thiaminase is better than on frozen food (I stated this in the article). However, I would not claim it to be safe. There is no study I am aware of analyzing the use of e.g. minnows as feeders and thiamin supply. I can only offer empirical hobby evidence of fish being fed goldfish and minnows leading to possibly/probably Thiaminase related diseases with the known results. I did not observe this with homebred mollies as feeders. My resulting measures and recommendations from working on the Thiaminase topic were simple: feed a varied diet, prefer Thiaminase poor food when possible and add vitamins to frozen food. I generally do not recommend feeder fish and rarely used them myself. Neale has a good article about the feeder fish topic:
I remember another study on tropical groupers, which came to the conclusion that internal organs should be removed of food fishes to avoid Thiaminase, this would also indicate that using feeders is not considered safe by the author, but I don't have it at hand right now. I think it was by Sih-Yang Sim et al., who wrote the "A Practical Guide to Feeds and Feed Management for Cultured Groupers" in which the Thiaminase avoidance recommendation is also briefly noted.>
Thanks for the quick response, Rich
<Welcome. Cheers, Marco.>
Re Thiaminase   1/5/12

PS: A quick look at my literature re thiamin deficiency brought up a reference of a tropical fish species showing symptoms of  thiamin deficiency likely due to high thiamine activity in a food fish. It's Glezebrook an Campell "Diseases of Barramundi L. calcarifer in Australia: A Review". I'm citing : "Nutritional deficiencies have begun to appear in cultured barramundi. Six out of a group of 60 fingerlings being reared in a plastic lined swimming pool in Cairns were exhibiting abnormal swimming behaviour, i.e. nearly vertical with exaggerated tail movements. These fish were not interested in food and showed no obvious internal or external lesions. Microscopically, bilateral degenerative changes (vacuolation) had occurred on both sides of the brain and the peripheral nerves were also affected. In the spinal cord, gliosis, i.e. swelling of the glial cells, was evident, particularly ventrolaterally. There was strong evidence to suggest that fish being fed to the fingerlings was high in the enzyme Thiaminase. A dietary change has since corrected the problem." So apparently tropical predatory fishes can suffer from Thiaminase! I don't know if they've been fed live or frozen fish, though.
Re Thiaminase 1/7/12

This email was an addendum to an answer I send to Richard re Thiaminase. It should go to where the earlier answers went. I could not answer his original email at this point, because I had it already answered and deleted and couldn't find it in the deleted emails' folder. Hope that's no problem.
<Real good Marco. Will do. BobF>
Thiaminase... repeated

<PS: A quick look at my literature re thiamin deficiency brought up a reference of a tropical fish species showing symptoms of  thiamin deficiency likely due to high thiamine activity in a food fish. It's Glezebrook an Campell "Diseases of Barramundi L. calcarifer in Australia: A Review". I'm citing : "Nutritional deficiencies have begun to appear in cultured barramundi. Six out of a group of 60 fingerlings being reared in a plastic lined swimming pool in Cairns were exhibiting abnormal swimming behaviour, i.e. nearly vertical with exaggerated tail movements. These fish were not interested in food and showed no obvious internal or external lesions. Microscopically, bilateral degenerative changes (vacuolation) had occurred on both sides of the brain and the peripheral nerves were also affected. In the spinal cord, gliosis, i.e. swelling of the glial cells, was evident, particularly ventrolaterally. There was strong evidence to suggest that fish being fed to the fingerlings was high in the enzyme Thiaminase. A dietary change has since corrected the problem." So apparently tropical predatory fishes can suffer from Thiaminase! I don't know if they've been fed live or frozen fish, though. Marco.>
Re: Thiaminase 1/7/12

I appreciate seeing others who take the responsibility of keeping fish equally as seriously as I do.  In reading the wet web’s report on Thiaminase and other topics I could tell how much thought and work went into each report, which I respect.  I have
a prejudice towards feeders, but if they truly are harmful to a tank then I’ll beat that drum. I feel that the problems associated with feeder fish are more related to poor tank management and ignorance than in the value of feeders.  However, if
nutritionally they are inferior, or even just equal to, pelleted diets, then there is no real use for them other than to stimulate natural behavior.  I think that has to be the starting point.
<I agree.>
I found the paper you cited and yes there is no way of knowing if the Barramundi were fed live or not. In my experience older research did not see the relevance of the distinction.
<No it didn't. The only thing you will find is that fresh fish (and therefore feeders as well) has a higher relation of thiamin to Thiaminase and therefore is better than frozen food. The question is: is it safe?>
Several months ago I had a conversation with Jim Zajicek of the USGS.  He is a wealth of information on Thiaminase research and was co-author of the Lake Trout study.  Very open individual and more than willing to let you bend his ear.  His email is and I’d introduce yourself.  His bottom line was that unless you were interested in breeding cold-water species, feeding live Thiaminase containing fish was not a nutritional concern.  With regards to warm-water species, he
said it was a non-factor. I also contacted Andy Goodwin at the Pine Bluff aquaculture facility and he put the question to a panel of fish nutritionist and no one on the panel voiced a concern. But, I fear you are correct in saying that the research on the topic as it relates to tropical fish is nonexistent.
<Yes, that's the problem. We have good points for both opinions.>
 This spring I am setting up an old tank system and should have some extra space.  I thought it would be fun to run a trial.   I want to take three groups of fingerling bluegill and raise them on three unique diets and then compare the results in the Fall.  One group I would rear on Gambusia (non-Thiaminase species), one on goldfish (Thiaminase containing species) and a control on a pelleted diet.  Some feedback on what you think a fair trail would look like, and any other comments, would be very useful.
<This sounds like a very good idea. Results should be published. Your control group will let you distinguish between live vs. pelleted food, personally I'd add a group fed with frozen, Thiaminase containing food to see if the bluegill are affected at all during the experiment (the barramundi apparently were affected much quicker than trout). What also would be highly interesting is the respective Thiaminase activities of the food types used (I don't know if properly raised goldfish fed with a healthy diet have a better thiamin/Thiaminase relation than the ones you get from crowded store tanks). I'd also add a second stage to the experiment where fish showing symptoms are fed (if they still accept food) a varied, thiamin rich and Thiaminase poor diet to see if the deficiency diseases are reversible at an early stage.>
Thanks. Sincerely, Richard
<Cheers, Marco.>
Re: Thiaminase
I’ll keep you informed on plans for a feed trial as they develop.  It is planned to begin in March when the weather warms up.  The first priority will be to address Thiaminase.  I like your idea of feeding one group a diet known to be thiamin deficient.  I worry though as the number of unique diets increases that the answers may get more muddled.  I am fortunate to have contact with some great people in the industry.  I don’t know where you are located
but I spoke with Steve Lambourne from LA last week about my plans.  Steve’s family has been importing and selling tropical fish wholesale for nearly 50 years.  He has one of the best reputations for quality on the West Coast.  He reminded me that for many years goldfish were believed to be the perfect food.  Oscar owners fed their fish a goldfish exclusive diet for years on end.  This began to change when Jack Gratzek and the University of Georgia linked a goldfish exclusive diet to HITH.  Adding variety to the diet cured the symptoms.  This is a point that we all take for granted now.  What is interesting though is that we
forget that an all goldfish diet use to be the norm and that it  supported good health and achieved good growth for many hobbyist. If Thiaminase is an issue with feeding live then why did those keeping Oscars not then find their fish lethargic, listless and dying after a few months?
<A lot hobbyists did observe according symptoms... see FAQs. Also, not all species are affected equally, we don't even know if all goldfish contain thiamin and Thiaminase and to what extent (this likely will depend on the goldfish diet.>
What we have is a study of the effect of a Thiaminase heavy diet on Lake Trout,
<and others...>
and an awareness that feeding frozen feeders leads to thiamin deficient like symptoms, leading us to make the illogical leap that feeders fed live will also cause a thiamin deficiency.  I say illogical because there are decades of practical fish keeping experience which say otherwise.
<Definitely disagree here as explained in detail before.>
The problem is that in the absence of good information we begin to draw conclusions that are not supported in the literature
or in common practice, but that is the point and the reason for the need for someone to step and start conducting feed trials.  Think about it though. Why in the 80’s and 90’s were Oscars fed an all goldfish diet able to
survive and grow to the size they did? 
<Many did not.>
The symptoms of beriberi develop in months and are pronounced.  If thiamin deficiency was occurring it would have been well documented, but it wasn’t.  At that time we didn’t know that goldfish contained Thiaminase.  If feeding live caused beriberi we wouldn’t have needed to wait until 2005 for a study of Lake Trout to bring it to our attention.
<It wasn't that study, which brought this to my attention, but observed symptoms. The study along with others only helped to explain the symptoms so far without a definite cause.>
It would have been studied and we would already have the data. The fact that the question hasn’t been asked has a lot to do with the fact that the problem didn’t exist.
<Definitely disagree here, too, for the obvious reasons written earlier.>
But, still the question has never been asked and studied directly and until it is there are going to be questions. Sincerely,
<Agree here. Cheers, Marco.>
Re: Thiaminase  1/10/12

Points well taken and I'll get started on a trial as soon as the weather warms up.
I propose to use five unique diets on the trial:
Group A) Top quality commercial pellet
Group B) Exclusive Thiaminase containing live diet (goldfish)
Group C) Exclusive Thiaminase containing frozen diet (goldfish)
Group D) Exclusive non-Thiaminase containing live diet (Gambusia)
Group E) Varied diet (goldfish, Gambusia, worms, snails etc...)
Each group will contain 10 bluegill in 75 gallon plastic tanks.  Each group of ten will be weighed and photographed prior to beginning the trial.  Periodically each group will be sampled.  In the Fall the entire group will be weighed and photographed with an average weight and length given. If there is a need individual fish can be dissected and inspected by a vet.
I suspect that the live diets will outperform the pellets.
<Bet the latter will be the most healthy group.>
That can't be assumed and I'll invest in an auto-feeder to ensure the pelleted diet gets fed at regular intervals.  It will also be interesting to see how the various live diets perform in relation to each other and how long it will take for thiamin deficiency to manifest in the frozen goldfish diet and or the live goldfish diet.
<Yes, I'm very interested if/when fish show any symptoms.>
The point of the trial is to get hard data.  I appreciate your interest and encouragement and will send you updates as the trial develops. I also want to encourage your sincere critique of the trial both as it unfolds and in the planning stage.
<The only thing I can add at the moment is: With your contacts to scientists that have worked on the topic, do you have the possibility to get a measurement of Thiaminase activity in one or two of your specific live and frozen goldfish samples? In case symptoms occur one could roughly compare them to other Thiaminase containing types of food.>
You are not going to hurt my feelings by pointing out something that I overlooked.  Thanks.
<Kudos to you for undertaking such a study.>
Sincerely, Rich
<Cheers, Marco.>
Re: Thiaminase  1/10/12
<"Bet the latter will be the most healthy group." should be the "last", being the varied diet (group E), not the pellets. I don't know how good the pellets will perform, but a varied diet in my opinion/experience should work best.>
Re: Thiaminase    1/11/12

The author of the Lake Trout study said he could do the testing for thiamin levels but that it was difficult and expensive.  Only maybe two labs in the world have the experience to pull it off.  You have to be able to isolate the Thiaminase in the tissue so that it does not interfere with the thiamin measurement. It is out of my price range.
<Okay. So, let's assume the goldfish do contain a similar activity as measured in earlier studies.>
However, most fish are a good source of protein and muscle contains a lot of thiamin so it is assumed that when feeding live of any species that there is an abundance of thiamin available from muscle tissue.  It is simply a question of how much is absorbed in the gut before Thiaminase deactivates it.  As it was described to me, "its all a matter of timing".  Also of note,  fish require only a very small amount of thiamin.  Their needs are measured in micro moles of B1.  In your experience with thiamin deficiency was it caused by using a frozen diet or did you see a deficiency using a live diet?
<Mostly frozen (including various warm water aquarium species). For live diets there are suspected cases of Scorpaenoids, Morays and Antennariids and a small number of freshwater predators such as Oscars fed exclusively goldfish.>
Also, how long did it take for symptoms to appear?
<My final words in the article: "Thiaminase-containing food will not be instantly lethal to your pets, but over the long term can result in a slow decline in health." A few months to about a year. I suppose with diets having at least a very little variation, it could take longer.>
One more thing, I was rereading your article on Thiaminase on the web last night.  It is inaccurate to say that Thiaminase will deplete existing B1 stores in a predator fish (if I understood you correctly).
<I think you refer to the sentence: "Furthermore, any fish fed such frozen fish will be consuming the Thiaminase, and that will destroy some of the Vitamin B1 it already has." An "eaten" or "in the gut" at the end would clarify that. This is about vit b1 in the stomach, gut.>
Thiaminase does not cross the blood barrier and remains in the gut where it passes out with the prey item.
<Yes, that's how I understood it.>
When feeding a varied diet it would then be important not to feed Thiaminase containing diet at the same time you feed a non-Thiaminase diet. Any B1 already in the predator fish is unaffected. The concern with using Thiaminase containing feeder fish is if enough B1 is absorbed to meet the future metabolic needs.
<Yes. See the fish groups noted above: Scorpaenoids, Morays and Antennariids: all have a slow digestion in relation to the temperature they live in. Plenty of time for Thiaminase to be active in the stomach. Barramundi on the other hand as well as mammals seem to digest faster compared to this group and still can suffer from the deficiency syndrome ( I assume they were fed frozen food, but don't know for sure for the barramundi). The species seems to play a role with Thiaminase: I remember a study where carp eggs (rich in Thiaminase) were fed to catfishes and sunfishes, and only the catfishes developed severe symptoms in the time of the study (a few months as far as I remember, will look it up if you want to read the study yourself). However, I have too little information on specific pet fishes to make even suggestions on which are more affected by a Thiaminase rich diet and which are less.>
Re: Thiaminase   1/11/12

Sorry to have challenged some of what you wrote, but the more we poke at this the more it make sense.  That is except for the barramundi paper which is an outlier.  I hadn't considered cold-water species of saltwater fish.
<Me neither, the groups I named are subtropical to tropical.>
That would be inline with the Lake Trout study.  In casual reading of claims of thiamin deficiency it would also appear that juveniles are more susceptible than adults. I haven't seen a paper supporting this, but it would make sense too.  With cold-water species it would be important to not feed a continuous diet of Thiaminase containing fish but to alternate weekly or find an economical source of non-Thiaminase containing fish. That seems to be a problem.  Non-Thiaminase containing species are usually more expensive and often frozen which cause other nutritional concerns. For fry I would recommend not feeding Thiaminase containing food. Fry usually feed on insects and other high protein items and don't have the opportunity to feed on other fish.  So there are good situations where Thiaminase can be a problem.  A manageable problem, but something that we need to be aware of.  But, I think we are painting in very broad strokes because of a lack of understanding of how Thiaminase works and that with warm-water species Thiaminase is not an issue.
<I doubt the latter as explained earlier. Just think about how long digestion takes at a frogfish or moray.>
Would you like me to recontact Jim at USGS and ask that question of him specifically?
<Question? You mean if warm water fishes such as barramundi or morays can be affected? Feel free to ask for his opinion and maybe link him to the barramundi study.>
I think he would be very interested in your observations as well.
Sincerely, Rich
<Cheers, Marco.>
Re: Thiaminase   1/12/12

I'll put the question to him. It might be a while before I get an answer.
Should be interesting.
How are things in Germany? 
<Quite fine. Thanks for asking. Surprising amount of work even for geologists like me. Also an interesting aquarium hobby scene with a lot in common to the US scene, but also differences.>
I've never made it there.  I bicycled once up from Madrid to the edge of the Rhine but then headed back to Paris for a flight out. I've always wanted to get back. Rich
<Hopefully you'll find the possibility. Cheers, Marco.>
Re: Thiaminase     1/24/12

How are you?  Hope all is well.
<Yes, thanks.>
Jim called from USGS and we talked about the barramundi paper briefly before he had to go to an appointment.  As you know there is a lot of detail missing in the account and he wasn't able to make much of it.  He is requesting the full article and some of the papers cited but he noted that none of the cited literature dealt with thiamin but rather B6 and B12.
<There are no citations within the paragraphs on Thiaminase in this article...>
He wanted to be clear that I understood that even though there was no definitive study that shows a link between feeding tropical fish live Thiaminase containing fish and thiamin deficiency that does not mean it does not exist.
<As noted before I don't think there is such a study.>
He went further to explain that not all Thiaminase is the same and its origins and purpose are very unclear as well as how it is stored.  In my opinion though, I don't think the article should be elevated to the level of being cited as a scientific reference to Thiaminase as its conclusions are anecdotal and the literature cited does not support the conclusion.
<I think you shouldn't simply exclude those references of which you don't like the results... It's not much, but it is as far as I know the only study at least touching the topic of Thiaminase and tropical fishes. And what needs to be noted, there is no study to my knowledge (anecdotal or not) that shows Thiaminase is a non-factor for tropical fishes.>
It gives the paper too much weight for what it is. If I find a good citation that shows a link I will pass it on to you.
He agrees that feed trials would be a good place to start and hopefully that will lead to a better understanding of the utility of feeder fish and their value. In reference to the saltwater species we didn't discuss those. The reason I think was that he had no experience and knew of no literature concerning them and Thiaminase and so he saw no point in discussing it. We are going to continue to communicate and I swap citations. Take care, Rich
<Okay. Thanks for the update. Marco.>
PS: And again I have to send a second mail due to a literature reference I did not mention: The book Marine fish culture deals with Snooks and notes thiamin deficiency (page 410). On page 515 it is also mentioned that "Thiaminase-induced athiaminosis could occur in in juveniles given fresh or frozen foods." I think more is found in "Snook and Tarpon Snook Culture and Preliminary Evaluation for Commercial Farming" by the same author (1987), but I don't have it at hand at home (likely would have to visit the lib). In addition to the one on groupers (one of the earlier mails) this makes 3 studies noting probable Thiaminase related problems with tropical fishes.

Fresh Water Fish Roe as Food for Salt Water Fish  /RMF   7/19/11
Is fresh water fish roe a bad thing to feed to the inhabitants of a reef?
<In general no; it's fine; though there are some toxic species...>
I ask because I want to start making my own fish/reef food and since I like to fish, I would hate to waste the roe of fresh water fish that I catch.
Chuck Furr
<If you/d eat it, it's fine for your marine fishes. Bob Fenner>
Fresh Water Fish Roe as Food for Salt Water Fish  /Neale   7/19/11
Is fresh water fish roe a bad thing to feed to the inhabitants of a reef? I ask because I want to start making my own fish/reef food and since I like to fish, I would hate to waste the roe of fresh water fish that I catch.
<As an occasional addition it's unlikely to do harm and should provide useful fats and proteins in particular. Certainly, feeding marine roe to freshwater fish does no harm at all. But at a broader level, do understand that many freshwater fish contain thiaminase, and that makes them best used as occasional rather than regular additions to the diet, and furthermore, there's a subtly distinct nutrient make-up in freshwater animals when compared to saltwater ones. While freshwater animals seem to be extremely
adaptable, many marine animals seem to depend on specific nutrients they receive directly or indirectly from marine plankton, so foods with a marine origin are crucial to the long-term success of marine livestock. Hope this helps, Neale.>




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