Breeding Aquarium Fish - Spawning Mops
Very many fish can be considered to be plant spawners. These are fish that attach their eggs to an aquatic plant. The eggs are left to fend for themselves, but at least on hatching the fry are offered some protection by being amongst plant matter.
Spawning mops simulate the plant matter that the fish in the wild would spawn in. They provide a spawning site and allow easy collection. Of course the eggs may be left on the mops, but in this case, real plants (such as java moss, riccia, najas and very many more) may be used. The reason aquarists pick eggs vary; maybe to follow the embryos development, to avoid fungusing, but more often to supervise the hatchlings, and increase survival. Fry are usually very predatory towards other fry, and if different sizes are kept together a few individuals will often outcompete, and then eat their siblings.
A typical set up is as demonstrated in the illustration above. A pair or trio is left in a plain tank with mops. (Occasionally a third member of a trio will eat the eggs as they are laid, watch out!) The reason the tank is plain is to make the mops the only spawning substrate. Some fish may only need to go together for a short period, and as long as they are well conditioned, will lay adequate eggs in a few hours. Some species, (e.g. non annual killifish) will thrive permanently in a set up such as this, and with the addition of a filter will be perfectly happy amongst the mops. In a permanent set up, some plant matter can be added to help recycle fish wastes.
How to make a spawning mop | Picking eggs