Glossostigma elatinoides: grower data for a demanding carpet

What the grower data says

Tropica rates Glossostigma advanced, with high light and high CO2 demand, and calls it “a difficult plant demanding a lot of light” ^[1]. Aquasabi rates it difficult and requiring CO2 as well, though it puts light at medium and growth at fast ^[2]. Tropica’s growth field is blank, so its growth rating is not published.

Tropica’s description gives the mechanics behind the rating. The plant grows upwards if light is poor, so larger plants must not overshadow it; and CO2 addition and soft water “promote growth significantly” ^[1]. When Tropica trialed Monte Carlo, Glossostigma was one of the carpeting plants it was compared against ^[3].

Size and placement

It is among the smallest aquarium plants, 2–3 cm tall according to Tropica, which calls it a good foreground plant and notes its popularity in Japanese-inspired layouts ^[1]. Aquasabi lists it for the foreground and nano tanks, with a care height of 1–3 cm ^[2].

Planting

Tropica’s planting advice is specific: divide the pot into small clumps of roughly an eighth of a pot each and place them a few centimeters apart, which helps the plants grow together more quickly ^[1].

The light and CO2 implied by an “advanced, high, high” rating are covered on this site in PAR, PPFD and DLI and CO2 from KH and pH.

How it compares with other carpeting plants

Among the carpeting plants profiled on this site, Tropica’s ratings place Glossostigma in the most demanding group ^{[1, 4]}:

Plant	Difficulty	Light	CO2	Height (cm)
Glossostigma elatinoides	Advanced	High	High	3–5+
HC ‘Cuba’	Advanced	High	High	3–5+
Monte Carlo	Medium	Medium	Medium	3–5+
Eleocharis acicularis	Easy	Low	Low	10–15+

Only Glossostigma and HC ‘Cuba’ combine an advanced rating with high light and high CO2. For a tank without strong light and CO2 injection, Eleocharis acicularis, at the bottom of the table, is the lower-demand option of the four; the parameter table sorts every profiled plant by the same ratings.

Names and range

Glossostigma elatinoides (Benth.) Hook.f. is accepted in the World Checklist of Vascular Plants, in the family Phrymaceae; Bentham first described it as Tricholoma elatinoides ^[5]. Tropica’s description says it comes from New Zealand, while its origin field reads “Australia” ^[1]. The checklist covers both: its native range is New Zealand’s North and South Islands, New South Wales, Victoria, South Australia and Tasmania ^{[5, 6]}. WCVP records it as introduced in Japan ^[5].