I've got a bit of it growing emersed right now. Don't have space for it in my tanks ATM but it is a cool plant. Definitely a background species, as it gets pretty huge. I remember back when it first came to the U.S. a couple years back, introduced via the AGA convention... it went for $50 a stem back then. Within a year, it'd dropped to $5/stem and now it's $5/bunch LOL. It is perhaps a bit more needy than, say, Hygro corymbosa or H. difformis, but there are still notably tougher Hygro species out there (sp. 'Araguaia', for instance)
Nope, it's definitely a hygro! Hygrophila in general have very diverse foliage, even within a single species—compare, for instance, H. corymbosa 'Stricta' to H. corymbosa 'Angustifolia'—same species, very different-looking foliage. Add the likes of H. difformis, H. balsamica, etc., and it's not hard to fathom a pinnatifid leaf mixed in with the group. Within it's genus, it's foliage probably most resembles H. odora (which has much more delicate leaves, admittedly, but the shape isn't that far removed) And, if you expand your search to look at the very closely related genus Staurogyne, you'll see other examples of pinnatifid leaves—Staurogyne sp. 'Bihar', for instance.I wouldn't be surprised if it was reclassified to another genus, it's that different. Beautiful, good luck!