Bait tank pump & battery life

[seaslug]

I think I know the answer but.... My Thresher tank runs the battery down way too fast, especially if I am also running my fish finder from same battery.

Pump is a Tsunami T-500, 13.6V @ 1.9amps. If I restrict the water to avoid beating up the bait the battery probably wears down even quicker with the load increase.

If I go to a 6V battery the current should go down to half and therefore run the pump slower and longer... right?

This would also solve some of my problem with the fish finder operating erratically most likely.

Downside is carrying 2 batteries with no backup possible.

Any suggestions?