Hi James,
I've not personally had any experience with Bacopa Australis but came across it in my 2007/8 catalogue & was looking at it with interest possibly for my next tank? Here's a quote from Tropica:
"Bacopa australis was discovered in southern Brazil (australis = southern), and it does not come from Australia, as might otherwise be assumed from its name. Like the other Bacopa species, Bacopa australis is also easy to grow in an aquarium. Under certain conditions it creeps across the bottom to form an elegantly decorative light green cushion. When Bacopa australis grows in a good light, the leaves become reddish. It is easily propagated by taking side shoots and planting them in the substrate."
If anyone has been able to grow it like this I'd be interested to know the conditions?