I started off with a tiny bit and it's now covering half my 5 g, and i have 3 clumps of it in my 10g. I have the same conditions as above, quite low light and i hardly do anything to it, occasionally i take off the old leaves but usually just stick the vacuum end in among the plant and shake for the old its to come off.
I'd be really happy to give some away.. but I live in Australia, and shipping plants OS might be difficult (or illegal?).
It is a pretty slow-growing plant, until it gets to the stage where it's sprouting baby leaves off the old ones. After that, it seems to speed up quite a lot.
I found it goes absolutely stupid with growth in my NPT (which has higher light than it prefers in my other tanks, too), just tied to a rock. It doubled in size in just a couple of months, to the point where I just had to take it all out so that the other plants weren't missing out on light.
The NPT produces a little natural carbon, and a bit of tannins from the organic potting mix (and now some wood I just included), so I'm wondering whether this is what caused it to have such rapid/healthy growth.