As I said, I don't have a nearby electricity source,so have to power up using an extension cable. I do realise that it would be preferable to have a permanent installation,no can do. If I drain/fill as you suggest,I would still need a pump on an extension, so my thinking is why not filter as I pump, whenever I can i.e. dry weather, me keeping an eye on things electrical.
50 feet of hardcore and gravel.
I don't know what hardcore means, but 50 feet is not that far to dig a narrow trench. You can lay either a conduit or a direct burial cable in the trench. Conduit is preferred, since it's more protective of the wires and you can pull whatever you want through it and depending on it's size, you can add circuits later if needed.
In the UK hardcore is a load of rubble,bricks,etc. rolled to form a very hard surface over which to lay gravel or whatever as a surface usually about 6-9 inches deep for vehicles to roll over. But I take your point. At 78, time is of the essence for me.
5 small fish, last time I saw them, rudd and goldfish. Plants in margins,some floating, got lilies coming soon. Frogs are happy in the pond,also dragonflies(damsels).The first year the pond was clear it was areal pleasure-year three, and I spend most of the time finding ways to to clear algae,but the water is still very opaque.
