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Gravel Bed, More Eggs

Pseudomugil gertrudae Breeding Jar


Most of us are familiar with using marbles/large gravel on the bottom of Danio spawning tanks to conceal and protect scattered eggs from the parents.  That works very well, but I contend that this technique works well for spawning a much wider number of species than Danios.  Killiefish normally are considered mop-spawners and all the eggs are thought to be found in the mop.  This is true for some species but not for others.  As an example, I set up a spawning jar with a pair of Fundulopanchax  scheeli with a mop and included large gravel/ marbles underneath.  I might find 5 or so eggs daily in the mop, but when I siphoned out from under the gravel also, I would find 10 or 15 more eggs!  This is 2 or 3 times more than found in the mop.  This could be from this species having less adhesive eggs, not going as far into the mop to lay them, or that they sometimes lay them over the gravel.   When I used this same setup with Fundulopanchax gardneri, I could find no eggs in the gravel, just in the mop.  Their eggs seem more adhesive and are laid more deeply in the mop.  Another species that seems to drop some eggs in the gravel is Pseudomugil gertrudae, the Dwarf Blue-eyed Rainbow.  They are mop-spawners, but I often found up to 10 times more eggs in the gravel below than in the mop.  This species has a reputation for not laying many eggs, but it may be that most do not stay in the mop and end up being eaten.



When feeding and maintaining fish for breeding in this type set-up, it is necessary to siphon out from under the gravel at least a couple of times weekly to remove excess food and debris anyway, and collection of the eggs can be done at that time.  I use this setup for breeding Tetras also.  Few if any eggs are found in the mop from tetras, but there is no problem in collecting more than enough eggs.  When they report that a certain tetra species may lay around 100 eggs at a spawning, it may well be that 2 or 3 times that amount could be collected from a large-gravel covered bottom.  These small tank setups do well with a small sponge filter or small box filter.  A simple bubbler can be used, but that requires more frequent cleaning and water changes.  Try putting large gravel (around ½ inch diameter) on the bottom of breeding tanks of different species of fish, especially mop spawners, to see if more eggs could be collected.  Just remember, in a small tank, the eggs must be rinsed off and placed in fresh water after spawning.  You may be pleasantly surprised after siphoning under the gravel!

Male Dwarf Blue-eyed Rainbow