TankBud

Crazy fish

Butis butis

Also known as Duckbill sleeper, Upside-down sleeper

FreshwaterFish

Crazy fish (Butis butis)
The Wet Spot Tropical Fish · Used with permission

Care at a glance

Temperature
75–82°F
24–28°C
pH
7.0–8.2
Adult size
5.9 in
15 cm
Minimum tank
66 gal
250 L
Temperament
Aggressive
Social behavior
Solitary
Tankmates
With caution
Swim level
Bottom
Diet
Carnivore
Difficulty
Medium
Breeding
No record
Rarity
Rare
Family
Eleotridae
Origin
Indo-Pacific coastal waters

Overview

The crazy fish is a predatory sleeper goby that hunts from cover near the bottom. It is a fish for a keeper past the beginner stage.

Did you know

The crazy in the crazy fish's name is about orientation, not temper. It rests and even stalks prey at odd angles under a log, often head down, vertical or belly up. That is unusual balance control for a fish.

Caring for the crazy fish

House the crazy fish in at least 66 gal (250 L), with plenty of shade and cover. Furnish the tank with bogwood, rockwork and robust plants over a soft bottom. It lurks under wood and among roots, then lunges at passing prey.

Keep the water warm, hard and alkaline, at 75 to 82°F (24 to 28°C) and a pH of 7.0 to 8.2. Juveniles are sold and kept as freshwater fish. Long term, it often settles best in lightly brackish water with a little marine salt added.

It preys on small fish and crustaceans, so feed meaty foods such as earthworms, prawn pieces and frozen items. Wean it onto larger sinking foods over time.

The crazy fish is an ambush predator, and it will take any fish or shrimp that fits in its mouth. It ignores anything too large to swallow and is not a general bully. Keep it on its own or only with fish far too big to be eaten. Its aquarium breeding is not recorded, so it is kept as a single oddball rather than bred.

Good to know

Butis butis belongs to the sleeper goby family Eleotridae. It is also sold as the duckbill sleeper or the upside-down sleeper.

In the wild

The crazy fish ranges widely through Indo-Pacific coastal waters, from estuaries and mangroves to the fresh lower reaches of rivers. There it hangs motionless among roots and snags, waiting to ambush prey.

Common questions

What size tank does a crazy fish need?

A crazy fish needs at least 66 gal (250 L). It spends most of its time in the bottom.

What temperature and pH does a crazy fish need?

A crazy fish is comfortable at 75–82°F (24–28°C) with a pH of 7.0–8.2.

What does a crazy fish eat?

A crazy fish preys on small fish and crustaceans. Feed it meaty foods such as earthworms, prawn pieces and frozen items, and wean it onto larger sinking foods over time.

How big does a crazy fish get?

An adult crazy fish reaches about 5.9 in (15 cm).

Related species