The dimensions are 1 foot x about 6''. I am not sure if that is big enough - I hope it will be good for the first week at least.
There is no special cover to the basket, though I do conrtol how much it would float above the water surface, by the thickness of the foam I use to make the basket float. The pup's would need to jump in order to run away....
I do use a cover for the entire aquarium - and it is covering the basket as well.
So, everything is yet in theory, I would need to use it and only after could say it is a recommended way. I still cross my finger the bearth will be OK - and that I will catch the pup's on time to save them from being eaten.
Thanks,
Avishay