On an out-of-town trip yesterday, I picked up an Alternanthera reineckii
"roseafolia" = a red-purplish plant. It's now floating in my
moderately-lit plant aquarium, where it will be planted later.

Do you have any experience/ advice to share of this or similar plant?
Thanks!

Here's what Tropica's web site says "The purple colour underneath
Alternanthera reineckii ''roseafolia'' leaves provides an effective
contrast to the many green plants in an aquarium - particularly when
planted in groups. Good light encourages the leaves to turn red. Most
Alternanthera species are difficult to grow, but this one is relatively
undemanding. Easy to propagate by nipping off the terminal bud and
planting it in the bottom. This also makes the mother plant more bushy,
because more side shoots are formed."

The Tropica link is at http://www.tropica.dk/productcard_1.asp?id=023 .