Common Causes and Fixes for Arowana Underbite (Dou Zui)
📝 Summary
An arowana underbite (dou zui) is a lower jaw longer than the upper, like an underbite in humans, and hurts its looks. It is congenital (genetic, shows at 20-25 cm) or acquired from oversized food, a too-small tank, frights, or normal male mouthbrooding. Mild cases improve with a bigger tank, timed feeding, calm surroundings, and smaller varied food; severe cases are hard to reverse.
1 Arowana Underbite: Causes and How to Fix It
1. Causes of arowana underbite
It splits into congenital and acquired forms.
Congenital underbite is genetic and usually shows as the fish grows to 20-25 cm; diet adjustment rarely helps. So when picking a juvenile, study the mouth shape closely.
Acquired underbite relates to husbandry. An arowana swallows with the lower jaw, so the lower-jaw muscles strengthen with age and a slightly longer lower jaw is normal. But if the underbite is severe, fix it through proper feeding and other measures.
Causes of acquired underbite:
1. Food too large
Most underbites come from poor diet: chunks too big to chew and swallow comfortably, overfeeding and excess nutrition, long-term floating feeds, or irregular feeding that leaves the fish starving too long — all speed up the problem.
2. Tank too small
An arowana swims constantly; in a small tank it bumps the glass when turning, causing rapid breathing and a loose lower jaw. Over time the chin grows upward and an underbite appears.
3. Fright
Poor water quality or a noisy setting stresses the fish; frequent frights cause glass-bumping that can injure the lower-jaw bone and lead to underbite.
4. Normal male physiology
Past a certain age male arowana naturally develop an underbite, because during breeding the male mouthbroods the young and needs a larger lower jaw to hold more fry.
2. How to fix arowana underbite
1. Move the fish to a larger tank so it has a comfortable space and avoids bumping the glass and other discomforts.
2. Feed on a fixed schedule and amount, stopping at about 70-80% full. Do not starve it long (fast eating when fed) and do not overfeed (obesity, overgrown jaw fat).
3. Keep the surroundings quiet to avoid fright-induced glass bumps, underbite, or other disease.
4. Cut food smaller but keep it chewable so both jaws work without overusing the lower one. Vary the diet and do not feed floating food long term, to prevent underbite.
If the underbite is very severe, husbandry and surgery rarely fix it fully, so learn to accept it; but mild cases are easy to improve. Watch the mouth shape and adjust your care to leave underbite behind.
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