Fish Disease Diagnosis
Fish Disease Treatments
Ponds, Aquaria & Filtration

Fish Disease & Diagnosis
Fish Disease Treatments
Koi Keeping Basics
Ponds & Filtration
Case Histories
Water Quality & Testing
Using Your Microscope
Fish Disease Movies
Even More Movies
Useful Aquatic Links
Site Map
Topic Search
Frequently Asked Questions
Koi Health Book
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How can you tell if a Koi or goldfish is a boy or girl?

Gender in Koi.

Male koi and goldfish are more streamlined. Female Koi are usually shorter bodied and "full" through the shoulder area, especially just behind the gills.

Click to see larger imageMales in the springtime have breeding tubercles, which are (almost imperceptible) white spots on the gill covers and the leading ray of the pectoral fins. Females lack these tubercles.People are surprised that these breeding tubercles can be seen in Goldfish of three inch length and Koi of only six inch length in some cases.

These breeding tubercles are sometimes mistaken for "white spot disease" and harshly treated.

Fish disease problems? Need some help? The help pages take you through the basics of the 'fish health work-up' diagnosis method and basic fish disease treatment methods.

90% of all health problems and fish deaths are caused by poor fish keeping! The key pages are essential reading for all beginners and intermediates who are serious about disease prevention.

Expanded Content by Dr. Erik Johnson, and Used with Permission; Frank Prince-Iles ©2009 All Rights Reserved