Bro if you can get the white 5 gallon buckets and lids to go on the outside of the black buckets you will be much better off, the black on the inside will keep it nice and dark but the white on the outside will deflect the light and also black attracts light so you don't want the buckets to be this colour on the outside, also you want to get iceline tubes or the US equivalent as again they are white on outside and black on the inside which again keeps the res cool, you are spot on about the pump though, more air the better!
View attachment 876103