what are the tank dimensions? I think that's probably more important. They don't really need the height but the length and depth will be important. I'm sat looking at my 30 litre tank for instance and thinking 'I wouldn't put my pair in there, it's too small'. They'd probably be better in a 60 litre. You have to think that they could have as many as 200 fry and if 200 survive (which is unlikely, I know) there's no way a 45 litre tank could cope.
I had mine in my Juwel Rekord 800, which is 110 litres, measures 81cm long and 36cm deep. I had just 18 fry in there once and it was surprising how quickly they filled that tank.
The fry grow slowly to begin with but then get a growth spurt. Bearing in mind that you'd need to get them to around 2cm before you can move them on they'll soon out grow a smaller tank
Sorry for the edit, I was eating lunch and trying to reply and hit post too soon!