Do Guppies Contain Thiaminase? (What Fish Has It?)

Image of guppies without thiaminase

Guppies don’t contain thiaminase. There are no studies that indicate the presence of thiaminase in guppies. That is why guppies are generally considered to be safe from a thiaminase perspective. Hence, expert aquarists recommend the use of guppies as feeder fish instead of goldfish and minnows.

Let’s talk about this in detail now.

What Is Thiaminase? Why Does It Matter For Reptiles And Pets?

Vitamin B1 (Thiamine) is an essential nutrient for animal health.

This water-soluble vitamin helps the body convert food into energy. It plays an important role in neurological and cardiac health.

Thiamine is essential for the proper functioning of the nervous system.

Now, Thiaminase is an enzyme that breaks down Vitamin B1 or thiamine.

When it is present in the body, it neutralizes the activity of Vitamin B1. This can lead to Vitamin B1 deficiency over time.

Thiaminase is present in certain fish species, plants, African silkworms, and bacteria.

When animals consume them as prey, it affects their ability to metabolize Vitamin B1.

Thiaminase problems are common in garter snakes, turtles, fish, and reptiles in captivity that feed on fish.

In humans, the deficiency of Vitamin B1 causes a disease called beriberi.

In animals, thiamine deficiency causes neurological, muscular, and immune disorders.

Certain studies have shown that flatfish fed on thiaminase-rich diets ended up being paralyzed.

Reptiles like garter snakes can end up with seizures and convulsions due to Vitamin B1 deficiency.

If left unchecked, the condition will progressively worsen and kill the animal. Hence, we cannot easily overlook it.

Many reptile hobbyists and pet owners are unaware of the risks of thiaminase.

This can prove dangerous as offering live food containing thiaminase can pose a significant risk to their pets.

Why Doesn’t Thiaminase Create Such Problems In The Wild?

Thiaminase problems usually occur when you exclusively feed an animal with thiaminase-containing food.

This is more common in animals held in captivity since they have limited access to a varied diet.

In the wild, thiaminase-containing fish are aplenty. However, the predators will have access to a variety of animal nutrition.

As long as they consume a varied diet, the intake of thiaminase doesn’t create a problem. Hence, the animal stays healthy.

Now, the problem with feeder fish is that owners usually offer it in its original form or as frozen fish.

Freezing doesn’t affect thiaminase.

When you freeze fish containing thiaminase, this enzyme breaks down the Vitamin B1 that is naturally present in the meat.

It will thus reduce its nutritional quality completely by rendering the thiamine ineffective.

Additionally, feeding raw or thawed thiaminase-containing fish will introduce this enzyme into the body of the consumer.

Thiaminase will also act on the thiamine in its body, thereby worsening the thiamine deficiency.

However, cooking the fish will destroy thiaminase. So, feeding your pet with cooked fish will eliminate the thiaminase concern.

Guppies And Thiaminase

Thiaminase is present in various species of freshwater fish and shellfish. It includes both freshwater and marine fish.

Many varieties of aquarium fish and feeder fish, like goldfish and danios, contain thiaminase.

Hence, it’s not a good practice to use these fish as feed for pet reptiles and carnivorous fish.

Interestingly, guppies and platies are exempted from this list.

There is limited research on the presence of thiaminase in guppies.

However, the existing data suggest that this fish does not contain thiaminase.

Hence, guppies are a safe choice as feeder fish.

Nonetheless, a varied diet with nutrition from different sources would be the best way to avoid any vitamin deficiency problems.

What Fish Contain Thiaminase?

The following fish are found to contain thiaminase:

  • Californian Anchovy,
  • Broad-striped anchovy,
  • Barb,
  • White Bass,
  • Bowfin,
  • Bonefish,
  • Bream,
  • Butterfish,
  • Common Carps,
  • Hardhead Catfish,
  • Atlantic Cod,
  • Channel catfish,
  • Goatfish,
  • Atlantic and Baltic Herring,
  • Lamprey,
  • Jobfish,
  • Loaches,
  • Pacific Mackerel,
  • Milkfish,
  • Minnows,
  • Mullet,
  • Scaled Sardine,
  • Scad,
  • Sculpin,
  • Shiner,
  • Pond Smelt,
  • Ruby Snappers,
  • Suckerfish,
  • Swordfish,
  • Yellowfin Tuna,
  • Whitefish.

You will also find thiaminase in common freshwater and marine organisms like mussels, clams, shellfish, and aquatic invertebrates.

Different members of the same species of fish may also have varying amounts of thiaminase in them.

Now, if we look at the food groups used to feed predatorial pet animals, the most common prey are mussels, crustaceans, and cyprinids.

Common aquarium fish like goldfish, carps, minnows, and danios belong to the cyprinid family.

These are popular feeder fish because they are easily available.

However, they contain thiaminase. So, exclusively using such fish for feeding pets can lead to a serious thiamine deficiency.

It may not be the best option for your reptile or large fish pets.

Although it can take several months before the symptoms become significant, it can cause great damage and prove fatal for your pet.

Guppies As Feeder Fish

Many pet owners with reptiles like garter snakes or turtles use feeder fish for their pets.

Doing so stimulates the animals’ natural hunting instinct.

It also provides a varied diet with natural nutrients that store-bought food often lacks.

Guppies are popular feeder fish. The absence of thiaminase is one of the most important reasons.

Additionally, guppies are livebearers, which means they give birth to young ones.

They have a very short gestation period of fewer than 28 days.

A single guppy can have up to fifty young ones each time.

This ability of guppies to breed profusely makes them a cost-effective choice.

Most large fish and reptiles enjoy eating guppies.

However, as with any live food, guppies present the risk of introducing parasitic infections and diseases.

While you can buy feeder guppies from pet stores, it’s worth remembering that they rarely receive the same care as regular aquarium fish.

Any lapse in care can make them sick and unhealthy. Feeder guppies are often kept with sick and infected fish.

Hence, they are at higher risk of being infected themselves.

If you wish to use feeder guppies, the best choice is to breed them yourself. You can easily set up a tank for feeder guppies.

Choose a tank of the right size and fill it with water at the right pH.

Additionally, you will need an efficient filter and water heater to maintain the right water temperature.

Once your tank is ready, you can introduce a couple of healthy adult guppies into it.

It’s a good idea to keep more females than males to prevent any harassment of the females in the tank.

Buy your feeder guppy parents from a reliable store.

If the tank conditions are favorable, they will breed quickly and frequently. You will have guppy fry in a matter of months.

Since guppies don’t take too long to mature and reproduce, your tank will be full of guppies in no time.

The new offspring will also start reproducing by the time they are a few months old, hence ensuring that you have a ready stock of feeder fish for your pet.


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