The 180° Standard
A true halfmoon spreads its caudal fin in a perfect 180° semicircle when flared. The top and bottom rays touch an imaginary horizontal line through the middle of the body.
Fish under 180° are classified as super delta (170-179°) or delta (150-169°). Only a true 180° qualifies as halfmoon in IBC competition.
Common Faults
Rose tail: excessive ray branching causes the tail to curl back on itself. Looks spectacular but judges penalize asymmetry.
Tube ray: one or more rays point forward instead of radiating out. Creates gaps in the fan.
Rolled edges: fin tips curl under. Usually water quality or genetic weakness.
Breeding Strategy
Line-breed two 180°+ parents. Outcrossing to delta or super delta brings back old defects.
Cull aggressively — most spawns produce 5-10% competition-quality fish. The rest become pet-quality.
Grow-Out Conditions
Large grow-out containers (minimum 1 gallon per juvenile). Cramped quarters produce uneven fin development.
Daily water changes, warm temperature (80°F), and varied diet maximize fin potential.