Hi Kreos,
I like your water plant collection, really! You know, if I stayed at home for long, I would do exactly the same as you. Well, I don't want to bother my family with another plants...
In the meantime, I bought two tropical lilies a few years ago – it was a souvenir from Bangkok. One of them died shortly, but another one is doing pretty well. I've been growing it in a small pot, like 50 l. From late April till early October it spends time outside, all the rest of the time inside.
You wrote that you leave your lotus outside all winter – where exactly and what are the minimum temperatures they're able to survive? I'm wondering if they would be able to overwinter in my pond, in Poland, if I completely sink the plant in autumn?