so very ture, most all that have FOWLR either turn it into a reef or get another tank to start a reef, just a matter of time in most cases. go sump now if you can, but if you can not swing a sump now, you can always add it later without tearing down anything, the filtration is the same in a reef as it is in a FOWLR. but better yet why not just go with a reef now, the main dif is more water flow, lights and chemistry.