thank you and thank you for your help and support (and everyone else that's commented too!!)
One last question (for now) If/when they hatch, should I leave them in this bottle or set them free into this tiny 10 litre tank that my Dad has leant me? There's no filter in it, just a heater and air stone.
I am planning to take all my guppy and platy fry (in my 25 litre tank) down to my lfs early next week so the filter from there could be moved into this little tank as I want to strip the 25 litre tank down and give it a good clean.