Minimum Tank Size: 20 Gallons (75 Liters)
Care Level: Moderately Difficult
Water Conditions: 5.0-7.5 pH (Soft to Moderately Hard)
Temperature: 60-82.5°F (20-28°C)
Maximum Size: 1.25 inches (3.5 centimeters)
The Silver Hatchetfish (Gasteropelecus levis) is one of the more unique looking freshwater fish in the aquarium hobby, and its unusual body shape and attractive coloration makes it highly sought after by aquarists. The name ‘hatchetfish’ originates from its laterally compressed body, which resembles the head of a hatchet.
Silver hatchetfish are only found in the lower Amazon River basin in Brazil, and they inhabit streams, canals, and the shallow, dark waterways deep in the Amazon forest known as igarapés. They can also be found in floodplain lakes during the rainy season.
There are several species of hatchetfish available in the hobby, and to complicate matters, they are often sold under erroneous names. Most often, common hatchetfish (Gasteropelecus sternicla) are sold under the name ‘silver hatchetfish’, though they grow slightly larger and tend to be less shy.
Silver hatchetfish stay relatively small in the home aquarium, and they grow to just under 1 1/4 inches (3.5 centimeters). In captivity, there have been reports of them living up to five years, though on average, most tend to live for around three years.
The silver hatchetfish can take some time to acclimatize when first introduced to an aquarium, and it’s best to only add these fish to a mature tank. They tend to be very susceptible to ammonia in the water – even more so than other species of aquarium fish. This is why a mature aquarium is so important for them to thrive, as it usually won’t experience the same water parameter fluctuations that are so common in freshly setup tanks.
These fish spend most of their time near the surface, though some occasionally dwell in the middle of the water column. They are incredible jumpers, and can leap several feet out of the water. Several sources even go so far as to claim they can jump distances up to 9 feet (2.7 meters). Because of this, any tank containing these fish must be covered, or these fish will most likely leap out of the aquarium to their deaths.
These fish tend to be highly timid, although this can be somewhat alleviated by adding floating plants to their aquarium. They shelter in the dense hanging roots of plants in the wild, and mimicking this environment helps to reduce stress in silver hatchetfish.
Besides floatings plants, bogwood and driftwood can also be added to the aquarium, and the substrate should be a muted color. Some aquarists recommend covering the substrate in leaf litter, but the problems leaves can create often outweigh the benefits.
Because of their skittish nature, they tend to do best in a species only tank, and they will often have difficultly competing for food with other aggressive species of fish. However, silver hatchetfish may do well with peaceful bottom dwellers, such as bronze corydoras and bristlenose plecos – both of which make excellent tankmates for them.
Silver hatchetfish should be kept in groups of at least six. If they aren’t, they will often become highly stressed, and can even become ill. A group of six hatchetfish should be viewed as the bare minimum number required, and they only really thrive when kept in larger groups.
The best filter to use for these fish is a hang-on-back filter. Not only does a high quality filter like an Aquaclear Power Filter help to keep the water sparkling clean, but it also provides some much needed current for the fish.
These fish primarily feed on insects near the water’s surface, although they are also known to consume larvae, crustaceans and worms. With that being said, the vast majority of their diet is composed of insects (upwards of 90% in the wild), and this diet should be recreated as closely as possible in the home aquarium.
Most silver hatchetfish are reluctant to take prepared fish foods, but can be trained to eat them over time. When offering them dried food, I have found one of the very best is Hikari Micro Pellets, which promotes vibrant colors and has only the highest quality ingredients.
Until they can be transitioned to dried fish food, they should be fed live and frozen foods. The most readily accepted live foods are wingless fruit flies, daphnia, blackworms and gut loaded brine shrimp. Their taste in frozen foods is nearly identical to their live food preferences, and they will greedily accept frozen bloodworms, brine shrimp, daphnia, and blackworms.
These fish can be relatively difficult to sex, but the females are noticeably rounder than the males – especially when they are laden with eggs.
There is very little information available on breeding these fish, and at this time, there are no dependable resources detailing their breeding behavior.