Crocodile Toothpick Fish Species Profile: Size, Diet, Tank Mates & More

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Observing the behavior of crocodile toothpick fish can be both calming and rivetting. They’re slow, quiet, and tranquil in nature. They’re also remarkably curious fish, making them a joy to watch. 

This post includes all of the information about the crocodile toothpick fish that you need to know. This includes details on the tank size, food, water parameters, substrate, and more. 

By the end, you’ll be feeling more assured about what a crocodile toothpick is and how to properly care for it. 

Species Overview 

The crocodile toothpick fish, scientifically known as Indostomus Crocodilus, is an incredibly small fish that originates from Southeast Asia, where they reside in still freshwater. They’re commonly found throughout the southern regions of Thailand, but you can also find them in Peninsular Malaysia. 

Indostomus is a small group of fish consisting of only three recognized species, including I. crocodilus, I. paradoxus, and I. spinosus.

These fish are small and fragile, so those new to aquariums may struggle to keep groups of crocodile toothpick fish alive. They can’t swim so well either, meaning that more care and attention are needed. 

Therefore, it’s best for people with more experience with caring for fish to consider adding crocodile toothpick fish to their aquariums.

Scientific Name:Indostomus Crocodilus
Common Name:Crocodile toothpick fish
Origin:Southeast Asia
Size:1.2 inches (3 cm)
Lifespan:3 – 5 years
pH:5 to 7
Temperature:72 to 27 F (22 to 80 C)
KH: 0 – 5 dKH
Tank Size:5 Gallon


Indostomus Crocodilus (crocodile toothpick fish)

The crocodile toothpick fish is aptly named for its slender body with a crocodile-like head, tapering off to a fan-shaped tail. 

They are often mistaken for the toothpick fish (Vandellia cirrhosa) from the Amazon and pipefishes (Microphis spp.) due to their similar appearance.

The ventral, anal, and dorsal fins of male crocodile fish are accompanied by white seams. Males also have pelvic fins that curve inwards. In females, these pelvic fins are slimmer and straight. 

Female crocodile toothpick fish can easily be distinguished from males during breeding [1]. This is because their abdomens become increasingly large and rounded. The breeding process between males and females often happens in bamboo or other tubular aquatic environments. 

Males have black stripes on their fins and also show strong signs of guarding early on, which is a behavioral difference compared to females. 

Maximum Size 

The small size of crocodile toothpick fish is one of the main factors to consider when you’re thinking about keeping them in an aquarium. 

They only grow to 1.2 inches (3 cm) in length and remain fragile throughout their lifespan. As a result, extra care and attention are needed when caring for these fish. 

Crocodile Toothpick Fish Care 

In terms of their care, crocodile toothpick fish need the right tank setup and environment to stay healthy and thrive. This includes lots of swimming space, comfortable water parameters, and plenty of hiding spots.

However, if the idea of a challenge excites you, here’s what you need to know about caring for these fish. 

Tank Size

Tank size is one of the main challenges that people face when keeping a new species of fish. 

The ideal tank size for single crocodile toothpick fish is 5-10 gallons because of their petite size and low bioload. They are not school fish but a curious species, look better and display more interesting behaviors if you get groups of at least a half-dozen or more and put them against a lush plant background.

So, if you have multiple crocodile toothpick fish, you’ll need to expand this space accordingly. Add 5-10 gallons per extra fish.

Water Parameters

These fish can thrive in waters that are anywhere between 72 and 80 Fahrenheit. This provides you with a good range to choose from. 

In addition, the ph levels of the water should be 6.0-7.0, making it a marginally acidic environment which they prefer. You should aim for a water hardness of 0-99 ppm. 

You may also want to consider implementing a filter that increases the flow of water that provides 4-5 times the amount in your aquarium. This ensures that your fish get fresh water and are able to thrive. 

Decor (Plants and Substrate)

In their natural habitat, the Indostomus species prefer still freshwater. Therefore, they mostly reside in lakes, ponds, and streams. It’s also common to find them living near plants and algae. 

As mentioned above, it’s best to keep crocodile toothpick fish in a well-planted tank. Floating plants like duckweed and hornwort are good options for diffusing light. They will thank you as they prefer dimmer environments.

For substrate, a finer substrate material with decaying organic and plant matter, leaves, branches, and dirt is ideal. This will give them plenty of natural hiding spots and provide an aesthetic touch to your aquarium. 

These reclusive creatures are not often seen. They don’t startle easily, instead preferring to stay in the shadows until they feel it’s safe enough for them to explore their surroundings.

Oak leaves are recommended additions to the aquarium of crocodile toothpick fish, as they are known to contain tannins that aid in the health of your fish. Don’t overuse them, or your pH level will drop. A few leaves every few weeks is enough. 

Temperament & Tank Mates

Crocodile toothpick fish and corys
Photo: AquaMrs

Crocodile toothpick fish are towards the bottom of the food chain. Their small size makes them easy prey for large fish. 

It’s best to keep these fish alone or in a community tank with other peaceful fish or aquatic critters that are the same size. 

They aren’t too concerned with living in the same space as others of their species. Males sometimes become territorial towards rivals; However, they don’t cause harm to each other which is considerate of them.

One of the strange habits that they have involves swimming vertically. Some people become alarmed by this, but it’s pretty normal behavior for this species due to the way they perceive objects around them. 

Crocodile toothpick fish is more of a peaceful, curious species that simply enjoy hanging around the driftwood. Ideal tank mates for the black orchid betta include:

Food & Diet

A common mistake that people make is not feeding their crocodile fish. This is done based on the fact that these micro predators do not like prepared dried or frozen foods in the aquarium.

In the wild, crocodile toothpick fish primarily feed on tiny aquatic crustaceans, insect larvae, worms, and other zooplankton. However, things are different in an enclosed tank, even if there are plenty of plants and organic matter around. 

To mimic their natural diet, you should offer these fish small live foods such as daphnia, baby brine shrimp, nauplii, or micro worms.

In an established tank, naturally occurring macrofauna [2] that inhabits the soft substrate can also be an additional food source – another big plus when you have oak leaves at the bottom.


These fish are egg-layers. Breeding crocodile toothpick fish is possible, but it’s not easy since it’s a sort of rare fish in the hobby.

The best (or only) way to approach breeding this fish is to create a separate breeding tank with no less than 29 gallons. To ensure you have a bonded pair, start with a large breeding group of at least six individuals.

The tank should be heavily planted with plenty of driftwood and oak leaves so it has ample tiny microfauna and detritus for the fry to feed on.

Condition the adults with lots of high-quality proteins but avoid overfeeding.

Crocodile toothpick fish are sexually dimorphic. Males will have lighter bodies and bright dorsal and anal fins that are used to attract their female counterparts. When the male is ready, he will start to clean a spawning site and guard the area.

Spawning occurs near the entrance to the spawning site. Usually, males perform a variety of courtship rituals, such as erect fin displays, circling bouts, and quivering movements.

After spawning, the female will deposit as many as 40 eggs on the roof of the spawning site and then leaves the site. The male will protect the eggs until the fry become free-swimming.

Final Thoughts

Newbie aquarists may want to consider other types of fish first before deciding to keep crocodile toothpick fish. Their small size, fragility, and poor swimming abilities require the eye of a more seasoned aquarium owner. 

Owning these fish can be a fantastic experience due to how you can observe them exploring their curiosity. It can also be exciting to see how they react with other fish of the same species. 

If you’re still left with any questions about crocodile toothpick fish, please let us know! 

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Ivan Yeoh
Ivan Yeoh

I’ve been working with fish for the past 12 years, and I can honestly say that it has never been a dull day. In my time, I’ve worked at the largest fish farm in Singapore – so you could say I know a thing or two about keeping things running smoothly in watery environments.

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