I got some amazon frogbit off Oatfish a while back which is starting to take off now,I'd say the roots were about 10cm just now and I think they add a real natural touch.My gouramis love hanging out in them,and I dare say,if they got too long,they'd be very easy to just lift out and chop them.
Once they settled in,I had no problem with browning/rotting leaves,although I think at the start you could be forgiven for wanting to bin them,I don't think they travel well,unless they were boxed instead of bagged,as the leaves do bruise easily,but give it a bit of time to settle and they're great.