Acquire the five or six sparkling gourami together. Shoaling fish should always be acquired as a group, and while this species is not quite in the same "shoaling" meaning as would be corydoras or characins, cyprinids, etc, we do have the hierarchical component with gourami. [I don't dare mention cichlids again...

] Males of this species have been known to attack and kill rivals, and adding the group together
always works to avoid this...though individual fish may not always adhere to the norm for their species. But it is advisable.
I agree with the underlying reasoning, but this becomes a non-event with live plants. And I believe plants are intended in this tank. Floating plants are mandatory for the gourami. Water Sprite is your best, the dangling root masses will provide food and sites for bubble-nests. But the fish expects plant cover and this needs to be provided.
Floating plants are often termed "ammonia sinks" because of the amount of ammonia they can assimilate rapidly. Plants take up ammonia/ammonium as their preferred source of nitrogen, and studies have demonstrated that they are faster at assimilating ammonia/ammonium than the nitrifying bacteria. The latter will catch up, but the plants, if they are growing and fast-growing species like floaters are, will avoid any issue. Provided you do not overload the tank beyond its normal ability, you cannot have ammonia/cycling issues adding fish if floaters are growing.