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Killie Hatcher for Multiple Mop Spawners


When I first began to breed more than a couple of species of killiefish at a time, I found a monumental task in keeping separate each species’ eggs, dates laid, and other info.  All the petri dishes, pans, and freezer containers with eggs needing daily inspection and water changes were sitting there challenging me to keep track of which was which.  It seemed that there must be a better way to keep track and save time and space.  From a few ideas I had developed earlier in my fishroom, an egg hatcher was designed that is efficient and seems to work well.


It is a 2 ½ gallon plastic dishpan that holds prepared water which is continuously aerated and cleaned by a small filter.  Small individual floating containers which are numbered contain individual groups of eggs collected from the mops of different species.  Container number, species, and date collected are listed on a separate sheet of paper for easy referral.  The eggs lie on fine nylon mesh with filtered and oxygenated water circulating from below.  As many as 20 groups of eggs or species can be maintained and hatched in one dishpan at the same time.  The eggs are picked from the mop and placed in a cup with some prepared water.  Hold the floating container steady and pour the water and eggs into it.  Then record the container number, species, and date.  That’s all.  The daily inspection for fungused eggs is done on all containers in a few seconds, and water changes are done less often due to the filtration.  No opening and closing numerous individual containers.  Fungused eggs are easily seen and removed with an eye dropper.  It is readily apparent when the eggs hatch, and the fry are then moved to a grow-out tank with an eye dropper.  The water is specially prepared for the hatcher to retard fungus.  I use tap water treated with peat moss by running it through a power filter with peat moss in it for 6-8 hours.  I then add 2 teaspoons of salt per gallon.  The treated water should be clear and brown stained.  It is stable and does not require the addition of chemicals.  Rain or RO water could be used instead of tapwater if you are raising killie species that are difficult or sensitive.


  • 20 four or five ounce plastic cups.  I use disposable drinking cups from a dental office.  The top diameter is 2 ½ inches.

  • Waterproof glue.  I use a Thermogrip hot glue gun.  This works well on many items in the fish room.

  • 2 old pairs of pantyhose.  The unattached men will find this a most interesting challenge.  (2016 update:  find a substitute fine-mesh nylon material.  Times have changed!)

  • A dark colored plastic dishpan about 2 ½ gallon size, plus a rigid cover that blocks out light.

  • Styrofoam, one small block or sheet.

  • A small low-profile box filter with filter floss.

  • 20 rubber bands about 1 ½ inch diameter.

  • A permanent black marker pen.


Assembly of the killie hatcher first involves making the hatching containers.  Cut the plastic cups in two and save the top section.  Cut the pantyhose into twenty 3-inch squares, single thickness.  Then cut the Styrofoam into ½ inch cubes with a very sharp knife.  For each container, the pantyhose square is stretched over the larger end of the cup (lip) and held there with a rubber band.  The excess may be trimmed with scissors.  3 styrofoam cubes are evenly spaced and glued on the outside edge of the other, smaller end.  With the permanent black marker, the container number is put between the cubes so that it is easily seen from above.  When the egg containers are placed in water, they will float with the lip and nylon netting down where the eggs will rest.  Fill the dishpan with treated water, place the filter and cover, and you are ready to collect eggs!