Drop Eye
Drop eye is the most common arowana defect — one or both eyes angle permanently downward. It is cosmetic, not life-threatening, but it ruins the show value of the fish.
Causes: tank too short, overhead lighting too bright, fish trained to look down for sinking food, or fatty deposits behind the eye from overfeeding.
Prevention: 30+ inch wide tank, dim or no overhead lighting, surface ping-pong balls, alternating sinking and floating foods.
Treatment: surgery exists but is risky. Most cases resolve partially if causes are corrected within 6 months of onset.
Gill Curl
Gill curl is the curling outward of the gill cover, exposing the red gill filaments. Severe cases interfere with breathing.
Causes: inadequate water flow at the gills (tank too small, poor circulation), low oxygen, or chronic ammonia exposure during early growth.
Prevention: strong filtration, 2× tank volume turnover per hour, oversized aeration. Once curl sets, surgery (gill plate trim) is the only fix.
Bent Body / Spine Deformity
A bent spine in arowanas usually comes from being kept in too small a tank during the rapid growth phase (6–18 months). The fish grows in a curve to match the tank.
Once the spine sets, it is permanent. Prevention: never keep a juvenile arowana in a tank shorter than 5× its body length.
Ich and External Parasites
White spots on body and fins indicate ich (Ichthyophthirius multifiliis). Treat with: temperature raise to 86°F, salt at 1 tablespoon per 5 gallons, and quality medication (Kordon Ich Attack or formalin-based).
Arowanas are sensitive to copper-based medications. Dose at half-strength and monitor closely.
Internal Parasites
Wild-caught arowanas often carry intestinal worms and protozoa. Symptoms: thin body despite normal eating, white stringy feces, lethargy.
Treatment: Praziquantel (PraziPro) at standard dose for 7 days. Repeat in 3 weeks to break the parasite life cycle.