Pretty much yes.
Is the 15l cycled? If not then the ammonia will build up surprisingly fast and fry are particularly suceptible to ammonia poisoning. You'll need to grab a bit of filter media out of your main tank to boost the filter in the 15l to avoid this.
They only have little stomachs, chances are the 15l is quite clean? Ie. no build up of algae, micro organisms etc like in a mature running tank..? If so you're best feeding them a few times a day to avoid them starving. However don't feed them too much at a time.