Garden peat

Garden peat is the standard or staple spawning/incubation medium for many/most killifish enthusiast in North America. Cheap and readily available, a compressed "bale" would represent a multi-year supply for most hobbyist, with the excess finding a use "somewhere" in the garden or home. Garden peat varies in particle sizes within the product and you may want to sift/sort the finer particles and larger "twigs" from the the useable portion prior to use.

Many hobbyist recommend boiling peat prior to use; the target affect being reducing buoyancy, reduction in ammonia and decreasing the water altering characteristics (such as pH drop) associated with peat. If you do boil it, you may want to save the "extract" as it has many uses for conditioning coir & hatch water and reducing light penetration in water. The tannins in peat extract are thought to have a therapeutic affect on fish, but regardless your fishes colors will be enhanced when viewed through peat peat stained water.  Peat only has a slight "negative buoyancy" and will fly around the water column even when slightly disturbed. For this reason, it may be preferable to rinse out the fine particles a 2nd time prior to use.

Jiffy/Compressed Pellets

This commercially processed form of peat moss is a favorite with many hobbyist as it represents a exponentially larger volume of re-hydrated peat in a easily storable compact form. This products primary retail use is for starting seeds and cuttings. "Jiffy 7" peat is finely ground and then dehydrated to allow tight compaction. That said, "pellet peat" is akin to espresso coffee grounds as it has a stronger/more concentrated impact on water chemistry relative to a equal portion of garden peat. .

Fibrous (long strand) Peat

Shown lower right is fibrous peat in the re-hydrated state

If you should ever receive eggs in the mail from a European hobbyist, then it is likely packed in this material. While some European peat bogs may/may not differ in some ways from their Canadian counterparts, this long strand form is apparently readily available in Europe. In North America "fibrous peat" is often sold as a canister filter material or water conditioner and easily cost over $7 for about 1 fistful.

This material is excellent for resting eggs on top of if using the vaporization method of incubation, or it is equally useful for spreading across a submerged container of peat to hold down particulates' while the fish are spawning. For the latter purpose it can be re-used between spawns if boiled.

There is a 2nd form commercially available sold for use in Bonsai. It is midway between long strand peat and Garden peat in coarseness, price and other characteristics. It can be used as a substitute for either, especially when particulates are an issue. go here to Dallas Bonsai for more info.

Oak Leaf

Whether other hardwood species can be used as alternates is unknown, but one thing is certain: the leaves of most oaks (Quercus sp.) are fully safe for aquarium use especially after they have gone though the seasonal color change and drying. For most hobbyist, oak leaf is a easily obtainable free alternative than can be used in lieu of sphagnum peat for certain applications. Oak leaf contains tannins, and will have a similar, but milder effect as peat. You can optionally boil oak leaves for a short time to sterilize or re-hydrate, but usually a short stint in warm water will do the trick. If boiled, the extract makes a great water conditioner especially for fish hailing from tannin stained waters. Oak leaves usually release tannins at a slower rate than peat and in this respect may be a better alternative for small tanks if that effect is desired. 

Coconut Fiber (Coir)

Shown upper right is the dehydrated/compressed brick form, often sold for use as "Reptile bedding"

Shown lower right is coir in the re-hydrated state

Coconut fiber represents a viable alternative or total replacement for peat moss. In the case of hobbyist in Asian Pacific area & South America, it is the preferred choice or likely the only choice available. While some North American hobbyist have reported poor/no hatches using it; something else apparently is amiss or unknown here: since coir obviously works as a incubation media (or many oversees killifish breeders would have already dropped it from their repertoire) If your filtration or tank setup rules out garden peat, or the messy particulates peat presents proves bothersome, then try coir. Coir is heavier, less prone to clogging sponge filters, and has less impact on aquarium water chemistry. Coir doesn't require any preparation or boiling other than a short re-hydration in water. If you have any reservations about it's incubation uses, then perhaps prepare it with a 50/50 mix with garden or jiffy peat prior to storing/bagging your eggs.