How do I get the wen to grow?

Genetics first

A ranchu grows the wen its parents gave it. A fish from a line bred for heavy head growth will develop it in almost any decent conditions; a fish from a line bred for a refined Japanese outline never will, and should not. Before trying to force growth, ask what the fish was bred for. See the life stages page for when growth normally starts, usually in the second year.

What helps

• Protein. Frozen bloodworm, brine shrimp and daphnia several times a week, on top of a good sinking pellet or gel food with 40% or more protein. Growth needs building material.
• Warmth. Wen grows faster in the low to mid 70s °F (22 to 24 °C). It stalls in cold water. Raise temperature slowly and keep it steady.
• Clean, moderately hard water. High nitrate and soft water both slow growth. Weekly water changes and a GH of 8 to 15 give the best results.
• Green water. Breeders keep ranchu in lightly green outdoor tubs. The suspended algae buffer the water and provide constant grazing. It is one reason pond-raised fish outgrow tank fish.
• Space and low stress. A crowded or harassed fish spends its energy on cortisol, not on wen.

What does not help

• "Wen growth" additives and hormones sold online. There is no evidence for them and some are harmful.
• Overfeeding. More food than the fish can process becomes fat and nitrate, not wen.
• Trimming. Some breeders cut the wen to shape it. It is surgery, it needs anesthesia, and it is not for home keepers.

Keeping the wen healthy

The wen is soft tissue with folds that trap debris. White fuzz in the folds is usually a mild bacterial or fungal infection and it clears with cleaner water and 0.1 to 0.3% salt. Small white pimples that come and go are normal new growth. A wen that grows over the eyes on a Thai-style fish is not a problem for the fish; it finds food by smell.