I have another "not an orchid" post, but I was so happy to get blooms from this plant so here is a quick update.
The other night my Traub's spider lily (
Hymenocallis traubii) bloomed. This one is not currently growing in a riparium, but I did have it in the 120-gallon Mexico semi-biotope last year. I kept the bulbs dormant this winter and they began to grow right away when I potted them up in a terra cotta pot with clay gravel for growing in a container pond.
The foliage is only about 12" tall--many other spider lilies are bigger--so this plant has the right size and shape for growing in a riparium. The flower stalk grew somewhat taller, to about 15".