For a while they where all a similar size. They have a constant supply of small daphnia and chopped white worm and I was hoping the range on food size would suit the different sizes of larvae. I have a lot of aquatic plants to give some place to hide for the smaller ones. The behaviour of the larger larvae has become more jumpy, rather than just gently swimming.
At the moment I am not intending to separate them as I suspect the smaller ones may eventually not thrive, even if separated. I'll continue to supply lots of size appropriate food for both. I will try and get a photo showing the size differences over the next few days.