I have two 10 gal tanks with HOBs that I want to add double sponge filters to. They sit side by side. Should I get a double outlet pump or two single pumps? I also want to add another double sponge filter to my 40 gal Tall tank in another room, it also has a HOB. Do I get a double outlet for my 10 gallons and a single for my 40 gal? Do I get two double outlet pumps for all three tanks? Or do I get a single outlet for each tank? Plus what size and GPH do I get? Totally confused now.