Unless you have some other way to jet coolant through the fins, you need the fans.
Fans are useless when immersed in a fluid and will actually impede pumped flow... Considering the OP has not said *what* kind of fluid they are using (I hope to god it's not mineral oil) as long as the fluid is rather thin it's quite possible that positioning the miners vertically would give enough flow through them using convection alone with pumping only needed to circulate the fluid to the heat exchanger.