[laverda]

There is no reason you can not do as your thinking. It really is no different the running multiple tanks eith one sump. You do need to make sure your sump can handle the additional eater volume of the extra tanks when the retun pump is off. With 4 additional tanks it could be a substancial amount more. I am considering doing the same, but with just one long narrow shallow tank. There is no need for the complication of banimal overflow. Just put screens on both drains so snails or something can not get in them and cause a blockage. You could just have each tank have an overflow like a HOB filter with no drains to get blocked. Keep the elevation difference to a minimum to reduce noise.