i made a tank like yours out of my gatorade tank because the fish need electrolytes to stay hydrated.
I ran an inflow and outflow hose and it recycles the water better and having the cooler insulated the water stays at the same temp as in the ocean/lake/river, etc. I have it wired with my FF to my 12v 10.5 amp hour and it lasts nearly all day for a marathon of fishing.