My suspicion would be that it is B. monnieri, but I'm not sure you can tell. Mick.Dk is you best bet for a definitive answer.Does anyone actually think it's Ammania sp Bonsai?
If you kept a bit emersed you could tell when they flowered, because "Ammania" Bonsai is really a Rotala sp
shoot me a pm if its not what you wanted. I have some growing emersed and and in the tank you can have for the postage costs, I should have bought some off a UKAPS member I suppose.
pin them down horizontally and let nature do the hard work
Yes, the new internodes will be shorter, but it will always look a bit of an odd mixture. I'd definitely follow Mick.Dk's advice.Does higher light tend to make it grow more compact like the picture I posted further up? It looks very 'leggy' at the moment!
Cheers DarrelI'd let the plants grow and re-gain strength, for some weeks - then trim rather hard (= low) and re-plant the off-cuts in the group of cut stems. Rotala indica 'bonzai' is quite good at branching from cut stems (when in good health) and the off-cuts will hapily root and contribute to overall density of the group.