That Tom Barr used? Could it have been alternanthera reineckii lilacina? This has a nice purple underside under really good lighting. Or it could have been that one, as given enough CO2, light etc even bog plants can survive for a time in an aquarium.
As to that plant it gets described as 2 different plants regularly, some sellers sell it as hemigraphis colorata and say that it grows well in calcium rich aquariums, whilst most plant sites describe it as hemigraphis exotica and none aquatic. lol. From comparisons they are one and the same plant, and it only survives immersed for a few months. Pot it up if you want it to do really well, it will make a gorgeous house plant.
Ade