Thanks Helene,
You are right about Allan, even though I only spent about an hour with him I learned an awful lot.
For now I am adding paramecium to their tank. The day before the fry went in there I squeezed a sponge filter out into the tank to give some other natural organisms.
Their tank is currently only 2 litres, it has old oak leaves, java fern and java moss in there. I have not seen them since I released them in there – not sure whether they are still ok, but I have heard from lots of people that they disappear for a while – so fingers crossed.
I hatch live BBS twice a day as I have 30+ tanks with mostly smaller fish and lots of fry to rear. However, even the bigger fish seem to enjoy live BBS.