Can I plant in the aquasoil straight away?Updated a month ago

You can add easier species, but delicate/difficult species should be added after the tank has matured (in 2 or 3 weeks). Freshly submerged aquasoil is unstable and releases ammonia and other volatile substances. This environment is harsh on plants - hardier species are less affected, but delicate species can melt. When planting immediately, large and frequent water changes can mitigate most of the disadvantages of not allowing the tank to mature before planting.

The fast start:

This is for people who need to plant as soon as they submerge the soil. >70% water changes every other day for the first 2 weeks. This intensive water change schedule removes excess ammonia, algae spores and volatile organics emitted by freshly submerged soil. The removal of algae spores and organics allows plants to begin growing without being smothered by algae.

Additional steps to speed up tank maturation include seeding the tank/filter with mulm from older filters or starter bacteria, and maintaining a well oxygenated environment with 6X-10X water turnover.

Planting a large number of plants at the start will stabilise the tank more quickly, but you should still avoid planting species that are sensitive to biologically immature tanks, such as Bucephalandra and Utricularia gramminifolia. Delicate tissue culture species such as Hygrophila sp. Chai and Eriocaulon species should not be added until the tank is mature. For most tanks this will normally take at least 3 weeks.

A comprehensive guide with more details on how to stabilize a new tank fast can be found here.