Description
Rainbow Shark (Epalzeorhynchos frenatum)
Overview
The Rainbow Shark, Epalzeorhynchos frenatum, is a vibrant freshwater fish native to slow-moving rivers and streams in Southeast Asia, including Thailand and Laos. Despite its name, it is not a true shark but a cyprinid with a sleek, elongated body and striking coloration—typically dark gray to black with vivid red or orange fins. Popular in the aquarium trade, Rainbow Sharks are semi-aggressive and territorial, making them better suited for aquarists with some experience.
- Scientific Name: Epalzeorhynchos frenatum
- Size: 4–6 inches (10–15 cm)
- Lifespan: 4–8 years with optimal care
- Temperament: Semi-aggressive, territorial
- Tank Level: Bottom to mid-water column
Care Requirements
Rainbow Sharks are hardy but require specific conditions to thrive:
Tank Size: Minimum 50 gallons (189 liters) for a single Rainbow Shark. Larger tanks (75+ gallons) are recommended for community setups to reduce territorial disputes.
Water Parameters:
- Temperature: 75–81°F (24–27°C)
- pH: 6.5–7.5 (slightly acidic to neutral)
- Hardness: 5–15 dGH (soft to moderately hard water)
- Ammonia/Nitrite: 0 ppm
- Nitrate: <20 ppm
- Substrate: Smooth gravel or sand to prevent injury to their underbellies. Dark substrates enhance their fin coloration.
- Filtration: Strong filtration with moderate flow (e.g., canister filter) to maintain pristine water, as they are sensitive to poor water quality.
- Lighting: Moderate; they tolerate a range of lighting but prefer setups with shaded areas or caves.
- Decor: Provide caves, driftwood, and robust plants (e.g., Anubias, Java fern) for hiding spots and territory markers. Ensure ample open swimming space to accommodate their active nature.
Maintenance
- Water Changes: Perform 25–30% water changes weekly using dechlorinated water matched to tank parameters to maintain water quality.
- Tank Cleaning: Lightly vacuum substrate during water changes to remove debris, taking care not to disturb hiding spots or decor.
- Equipment Checks: Regularly inspect filters, heaters, and thermometers to ensure stable conditions, as Rainbow Sharks are sensitive to fluctuations.
- Territory Management: Rearrange decor periodically if aggression becomes an issue to disrupt established territories.
Diet
Rainbow Sharks are omnivorous with a preference for a varied diet:
Staple Diet: High-quality sinking pellets or flakes (e.g., Hikari Sinking Pellets, Omega One Freshwater Flakes).
Supplementary Foods:
- Live or frozen foods: Bloodworms, brine shrimp, daphnia.
- Blanched vegetables: Zucchini, cucumber, or spinach (secured to sink to the bottom).
- Algae wafers: Useful for grazing, as they consume some algae naturally.
Feeding Frequency: Feed small amounts 1–2 times daily, ensuring food reaches the bottom or mid-water column. Remove uneaten food after a few hours to prevent water fouling.
Note: They are active feeders but may compete aggressively for food in community tanks, so ensure all tankmates have access.
Behavior and Compatibility
Behavior: Rainbow Sharks are active, territorial, and semi-aggressive, often claiming caves or specific areas of the tank. They are most active at the bottom and mid-levels, occasionally darting to the surface. They may chase other fish, especially those with similar body shapes or bottom-dwelling habits, but aggression is rarely fatal if space is adequate.
Compatibility:
- Good Tankmates: Fast-moving, robust fish like larger tetras (e.g., emperor tetras, Nematobrycon palmeri), barbs (e.g., golden barbs, Puntius sachsii), danios, or rasboras. Peaceful mid- to top-dwelling fish that don’t invade their territory work well.
- Avoid: Other bottom-dwellers or similar-shaped fish (e.g., other Rainbow Sharks, Red-Tailed Sharks, loaches, or Corydoras like Corydoras sterbai). Avoid slow-moving, long-finned fish (e.g., guppies, bettas) and delicate species (e.g., glass catfish, Kryptopterus bicirrhis, or Otocinclus). Invertebrates like shrimp may be harassed.
- Social Needs: Best kept singly or in very large tanks (100+ gallons) with multiple territories if housing more than one. They do not school and prefer solitary or carefully managed community setups.
Reproduction
Breeding Rainbow Sharks in captivity is extremely rare and not well-documented:
Breeding Setup:
- Tank: A large (190+ liters) breeding tank with soft, slightly acidic water (pH 6.5–7.0, 5–10 dGH) and temperature around 25–27°F.
- Conditions: Include caves, plants (e.g., Java moss), and smooth surfaces for potential egg-laying. Dim lighting and strong filtration are essential.
- Group: Use a 1:1 male-to-female ratio. Males are slimmer with brighter fins; females are rounder and slightly duller.
Spawning Process:
Spawning is rarely observed but may be triggered by pristine water, a varied diet (live foods), and stable conditions.
Females may lay adhesive eggs in caves or on plants, which males fertilize, but specific egg counts and hatching times are undocumented.
Eggs, if laid, likely hatch in 2–5 days at 78°F, based on similar species.
Egg Care: Remove adults post-spawning to prevent egg predation. Maintain excellent water quality and consider antifungal treatments like methylene blue.
Fry Care: If successful, feed fry infusoria or liquid fry food, transitioning to baby brine shrimp or crushed flakes. Fry are likely delicate and require pristine water.
Challenges: Breeding is nearly impossible in home aquariums due to their territorial nature and specific requirements. Most Rainbow Sharks in the trade are commercially bred or wild-caught.
Additional Tips
- Observation: Monitor for signs of stress or aggression (e.g., excessive chasing, faded colors, or hiding).
- Quarantine new fish and acclimate slowly to prevent shock.
- Enrichment: Provide caves and varied decor to establish territories and reduce stress. Ensure enough space to minimize aggression.
- Health Concerns: Susceptible to ich, fin rot, or stress-related illnesses, often due to poor water quality or tankmate conflicts. Treat with aquarium-safe medications and address underlying causes.
- Territorial Management: Use tank dividers or ample hiding spots in community tanks to reduce aggression toward tankmates.
Picture for illustrative purposes only. Either come in store to view available stock or request pictures to be sent to you.
Please Note: Due to variations within species resulting from age, region, sex, etc., the actual livestock may not look identical to the image. Approximate size range may also vary between individual specimens.
