Yes.

Absolutely

If they are the kind I'm thinking they are.......yes, and no. Yes, they will work for size but the tubs will be quite heavy and since the tubs are pretty flexible I think you may find they will be difficult to lift in and out of the pond. Just depends on your setup. I can just visualize those being really difficult to lift in and out of the pond without dumping them.
I use large black dishpans that I get from Walmart.

I was gonna use the same one, but rethunk that cuz of the weight and how it is positioned in my pond...went with the same black dishpan thingys mentioned!It was just the matter of access.