How to Identify Hatchetfish Eggs in Your Aquarium

You noticed small spherical objects in your tank and wonder: could these be hatchetfish eggs?

Hatchetfish eggs are approximately 1 mm in diameter, translucent or slightly clear, and sink to the bottom of the tank rather than floating. Unlike snail eggs which appear as gelatinous blobs or pink masses above the waterline, hatchetfish eggs scatter freely among plants and substrate with no parental care.

Why Hatchetfish Eggs Sink (Not Float)

This surprises many beginners. Hatchetfish are surface dwellers, so you might expect their eggs to float near the surface. But that is not what happens.

According to a breeding report published in Tropical Fish Hobbyist magazine, blackwing hatchetfish (Carnegiella marthae) eggs “lay freely on the bottom” and hatch in approximately two days. The eggs are non-adhesive and scatter among fine-leaved plants or settle on the substrate.

Some sources mention eggs floating among plants, but the confirmed breeding observation states they sink. This creates confusion for hobbyists trying to identify mystery eggs.

Distinguishing Hatchetfish Eggs From Other Aquarium Eggs

The key clues are location, appearance, and what species you actually have in your tank.

Comparison Table

Egg Type	Size	Appearance	Location
Hatchetfish	~1 mm	Translucent, clear	Scattered on substrate or plants
Mystery Snail	2-3 mm cluster	Pink/cream calcified mass	Above waterline on glass or lid
Ramshorn Snail	1-2 mm blob	Clear jelly with embryos	On glass, plant leaves underwater
Amano Shrimp	0.5 mm	Greenish, carried by female	Under female’s abdomen (berried)

How to Use Location as Your First Clue

Check where you found the eggs:

1. Above the waterline: Almost certainly mystery snail or apple snail eggs. These form pink or cream-colored calcified clutches stuck to the glass above water.

2. In a jelly blob on surfaces underwater: Likely ramshorn or bladder snail eggs. These look like clear gelatin masses with visible embryos inside.

3. Attached to a female shrimp’s tail: Shrimp eggs. A “berried” female carries eggs under her abdomen for several weeks.

4. Scattered loosely on substrate or plants: Could be egg-scattering fish like hatchetfish, tetras, or danios.

Check Your Tank Stock

You cannot have hatchetfish eggs without hatchetfish in the tank. Before assuming eggs belong to a specific species, verify:

• Do you have hatchetfish? (Blackwing, marble, silver, etc.)
• Do you have mystery snails or apple snails?
• Do you have Amano shrimp or other shrimp species?
• Do you have other egg-scattering fish like tetras, danios, or barbs?

Multiple potential egg-layers in one tank make identification harder.

What Hatchetfish Eggs Look Like

Based on confirmed reports:

• Size: Approximately 1 mm diameter (tiny, like a grain of sand)
• Color: Translucent, clear, or slightly white
• Texture: Non-adhesive, they do not stick to surfaces
• Location: Scatter freely on bottom or among plants
• Behavior: No parental care; parents may eat them

Fertilized eggs may show a tiny dark spot (oculus or germinal vesicle) visible with magnification. Unfertilized eggs turn white and fuzzy within a day.

A Real Identification Challenge

A Reddit user posted photos of eggs falling from dwarf water lettuce in a tank containing hatchetfish, mystery snails, and Amano shrimp. Commenters debated what species laid them.

The eggs appeared larger than 1 mm in the photos, leading some to suggest mystery snail eggs fallen from a clutch above water. Others pointed to Amano shrimp eggs.

The uncertainty demonstrates a key lesson: visual identification without scale reference is unreliable. Multiple species in one tank compound the problem.

What to Do If You Find Potential Hatchetfish Eggs

If you believe you have hatchetfish eggs and want to attempt raising them:

1. Remove eggs immediately: Hatchetfish eat their own eggs. Transfer eggs to a separate container.

2. Use soft, acidic water: pH 6.0-7.0, soft water matches their natural Amazon basin conditions.

3. Keep eggs in dim light: Bright light may harm developing embryos.

4. Wait about 2 days: According to the TFH report, eggs hatch in approximately 48 hours.

5. Prepare microscopic first foods: Newly hatched fry need infusoria or liquid fry food; they cannot eat commercial flakes.

Note: Successful aquarium breeding of blackwing hatchetfish has not been widely documented. Most hatchetfish in the trade are wild-caught.

Common Identification Mistakes

1. Assuming floating fish eggs: Many beginners expect surface-dwelling fish to have floating eggs. Hatchetfish eggs sink.

2. Ignoring snail eggs: Snail eggs are far more common. Check for mystery snail clutches above water or ramshorn blobs on glass.

3. Overlooking shrimp: Female shrimp carry eggs visibly. Check your shrimp before assuming loose eggs are fish eggs.

4. Misjudging size: Without reference, photos make eggs look larger than they are. 1 mm is tiny; use a ruler or coin for scale if possible.

5. Assuming one species: Tanks often contain multiple egg-layers. Cross-reference all inhabitants.

Quick Reference

Clue	Likely Egg Type
Pink mass above water	Mystery snail
Jelly blob on glass/leaves	Ramshorn snail
Eggs under shrimp tail	Shrimp (berried female)
Tiny scattered spheres on bottom	Egg-scattering fish (if you have them)

Summary

Hatchetfish eggs are tiny (1 mm), translucent, and sink to the substrate. Identify mystery eggs by checking location first, then appearance, then cross-referencing with your tank’s inhabitants. Snail eggs above water or in jelly blobs underwater are far more common than fish eggs. Multiple species in one tank make identification uncertain without scale reference. If you want to raise hatchetfish eggs, remove them promptly before parents eat them and provide soft, acidic water conditions.