Rainbow Shark (Epalzeorhynchos frenatum)

The Rainbow Shark (Epalzeorhynchos frenatum) is a bold, jet-black freshwater "shark" from Thailand with fiery red-orange fins — a showstopper for medium and large aquariums. Despite the name, it's not a true shark; it's a freshwater cyprinid that patrols the bottom and lower mid-water, claiming territory and adding constant motion to your display. Best for intermediate keepers who can give it space and the right tank mates. Each fish is hand-picked from our display systems at Squeaky's Aquatics.

Rainbow Sharks shine in fast-moving community tanks — pair them with active mid- and top-dwellers like Zebra Danios, larger tetras such as Black Skirt Tetras, or a Dwarf Gourami. Browse our full freshwater fish collection for more compatible community fish.

Care Guide

• Care Level: Intermediate — hardy and easy to feed, but territorial behavior requires careful stocking.
• Tank Size: 55+ gallons recommended for an adult, with a long footprint (48"+) so the shark has territory to patrol without crowding tank mates.
• Water Temperature: 72–79°F (22–26°C).
• pH: 6.5–7.5 — tolerates a wide neutral range.
• Hardness: 5–15 dGH.
• Diet: Omnivore. Feed sinking pellets like Hikari Cichlid Gold, algae wafers, and blanched veggies (zucchini, spinach), with occasional frozen brine shrimp or bloodworms for protein. They'll graze algae and biofilm off décor.
• Lifespan: 5–8 years with good care.
• Décor: Provide multiple caves and hides — driftwood, rock caves, and dense plants break sightlines and reduce aggression. Sand or smooth gravel substrate is best.
• Filtration: Strong filtration with gentle current; they appreciate well-oxygenated water.
• Lid required: Yes — Rainbow Sharks are powerful swimmers and can jump.

Specifications

Compatibility

One Rainbow Shark per tank. Same-species aggression is intense — adults will fight to the death over territory. The only exception is very large, heavily aquascaped tanks (75+ gallons with extensive sightline breaks), and even then it's risky.

Good tank mates: fast active mid- and top-dwelling community fish that stay out of the bottom zone — Zebra Danios, giant danios, larger tetras like Black Skirts and Bleeding Hearts, rainbowfish, larger barbs (tiger, cherry), gouramis, and rainbowfish.

Avoid: other Rainbow Sharks, Red-tailed Black Sharks, plecos, loaches, Corydoras, and any other bottom-dwelling fish (the Rainbow Shark will harass them out of its territory). Skip slow long-finned fish like bettas — they're easy targets for fin nipping. Don't pair with small timid fish that won't hold their own.

Recommended Foods & Supplies

• Hikari Cichlid Gold Pellet — high-quality sinking pellet, perfect staple for Rainbow Sharks.
• Hikari Texas Holey Rock Cave — gives the shark a defendable territory and breaks sightlines.
• Mopani Driftwood — natural-looking hardscape for hides and biofilm grazing.
• Seachem Prime — conditions tap water and detoxifies ammonia between water changes.
• Browse all fish foods for sinking pellets, algae wafers, and frozen foods.

FAQ

Will it attack my other fish?
Rainbow Sharks claim a bottom territory and will chase off anything that enters — especially other bottom dwellers. Active mid/top-level fish usually get ignored because they're not "in its zone." Aggression spikes during territorial disputes and at maturity (around 4 inches).

Can I keep two Rainbow Sharks together?
Not recommended. Same-species aggression is severe and usually escalates to one fish killing the other. If you absolutely want a group, you need a 125+ gallon tank with heavy aquascaping and sightline breaks — and even then results vary.

What size will it grow to?
About 6 inches (15 cm) at maturity, sometimes a touch larger in a big tank. They're surprisingly long — account for swimming room, not just gallons.

Do they really eat algae?
Yes, but they're not dedicated algae eaters like otocinclus or plecos. Think of algae grazing as a bonus — feed a proper omnivore diet to keep them healthy and colorful.

Are albino Rainbow Sharks different?
Same species, just a color morph (white body, red fins). Same care requirements, same temperament — and yes, they will fight each other and standard Rainbow Sharks the same way.