Spawning Rocks for CyprinidsBy Ray Katula
reprinted from American Currents, Winter 1992-1993
Killifish owners have long utilized yarn spawning-mops. They are greatly advantageous for a number of reasons. Foremost is the convenience of extracting eggs. Other advantages include the ease of providing spawning habitat and the ability to sterilize the mops easily, preventing eggs from fungusing.
Similarly conceived methods for spawning other types of fish would be welcome work-savers. Over the last two years, I have experimented with a method of obtaining eggs from Southern Redbelly Dace (Phoxinus erythrogaster) inviting them to spawn in pebbles. Since numerous other minnows utilize the spawning mounds of Nocomis chubs to perform their egg-laying, the following method might enhance the number of fry and ease of determining if your minnows have indeed spawned.
I used to hate disassembling a pebble pile to determine if the fish had spawned. This method can easily be modified to accommodate an artificial sunfish nest, which many minnows may also utilize as a spawning nest.
First of all, get a used-up margarine-container or something similar. Thoroughly clean it. The cover can be discarded. One or two puncture holes can be made at the bottom of the container. This allows drainage upon removal, and, if undergravel filtration is being used, will help to oxygenate the deeper portions of the container. Fill the container with pebbles--or marbles, if you prefer--and stack to form a mound. If you wish to simulate a sunfish nest, use a shallower dish to conform to gravel depth, then hollow out a depression.
Place the pebble-filled container in the desired section of your aquarium. Generally--and specifically for Phoxinus--the best choice appears to be slightly away from the current outflow. If suspicious that spawning has occurred, remove the container and examine the pebbles or marbles for possible eggs. If there are none, replace the spawning material and wait for future probable spawnings. If they have indeed spawned, place the container in a nursery tank and replace the spawning pebbles with a similar container for maximum fry output. In my personal situation, one spawn is enough to produce sufficient fry, but I hated the laborious task of checking for eggs with my previous methods.
Now that I have discussed the "pros" of such a set-up, I should mention a possible "con": food can become entrapped within the pebbles/marbles, and therefore a careful selection of menu items is advised. Feeding only live foods helps, and most food, in sufficient current, will pass over the spawning-rocks. Unless overfeeding occurs, the entrapment of food should be minimal. During spawning, this author utilizes heavy feedings of tubifex and white worms via a floating worm feeder, which is ideal for this set-up and minimizes debris entrapment.
Recently, some spawning-rocks were placed within the breeding tank of some shiners and they have colored-up noticeably. Apparently these spawning-rocks can be utilized for a large variety of cyprinids, and may provide an invaluable tool for maximizing hatches and easing determination of spawning.
Used with permission. Article copyright retained by author.