Breeding the 'Fathead Minnow'
By Woody Tews
From Splash, newsletter of the Milwaukee Aquarium Society
The Milwaukee Metropolitan Sewerage Department works with a firm called SF Analytical
Laboratories located at 6125 W. National Avenue in Milwaukee to determine when treated
sewage can be released into Lake Michigan. In their testing, the laboratory uses 3
creatures or organisms for their test results. They are; algae, tiny daphnia, and fathead
minnows. Mr. Jim Stark who is the manager of SF Analytical has provided me with all the
technical data regarding their experiments plus a video that he produced. I in turn then
will make this material available to our club library for anyone who is interested. All of
the procedures regarding this testing were most interesting but I will dwell on the
The minnow is so named because the males develop a large spongy growth on the top of
their heads. This growth helps them protect the eggs from would be predators. The males
average about 3 inches in length and the more slender females are about 2¼". Mr. Jim
Stark was kind enough to give me a tour of the laboratory and a comprehensive dissertation
regarding all the testing including the spawning of the fathead minnow.
The lab uses 15 gallon tanks divided into quarters with substrate. The substrate used
is ½ sections of 4 inch PVC about 4-5 inches in length. The temperature is maintained at
approximately 77 degrees Fahrenheit with 16 hours of lighting and 8 hours of darkness.
Regular aged tap water works fine although the lab has a well.
For my home experiments I used 10-gallon tanks at 75-80 degrees Fahrenheit with my aged
tap water. I used one pair for best results per tank. I never witnessed a spawning because
it seemed to occur early in the morning. I have a small window near the spawning area and
the natural coming of daylight seemed to be very important. When I would feed the fish, if
the males were inside the cave (formed by the substrate) it was usually a sign that they
had spawned. The female after spawning left the site to the protection of the male. The
eggs were sort of gelatin like in appearance and quite clear. I didnt count them but
I am sure there were on occasion a couple of hundred.
Five days seemed to be the norm for hatching. I would remove the substrate with the
eggs and put them in a shallow plastic pan (like they give you in the hospital). The pan
would hold about 3 inches of water, and I then floated the pan in a heated 10-gallon tank.
In addition I supplied an airstone for water movement along with a few drops of an
anti-fungal solution. In the beginning I fed infusoria created by adding dried banana
peels to containers with older used tank water. I also fed powdered egg yolk. After a week
to 10 days I fed baby brine shrimp and micro worms. When the fry became baby guppy size I
released them into the aquarium proper from the pan.
All fish are interesting but knowing the role that the fathead plays in the processing
of our drinking water made them appealing to me as a hobbyist. They are quite common in
the USA and that is why they are the industry standard for experimentation. Once again on
behalf of the Milwaukee Aquarium Society, and myself thank you Mr. Jim Stark of SF
Analytical Laboratories in Milwaukee, WI. Also a thank you to Mr. Eric Waldmer of the
Milwaukee Metropolitan Sewerage District who mailed me the detailed description of the
Biomonitoring testing process.