i am looking to purchase a RO/DI system that will not be too costly, but i can take with me easily when i move out of my apt if i chose to do so. i recently discovered alge growth in my reef, and after research have come to a conclusion that city water for top offs could be the main cause. i run a 40B reef, and dont think it would be necessary to have a holding tank because my water changes wouldnt be that big. please object or share ideas please. open to conversation.