Hey all. I've noticed that over filtering, and good flow of water around a planted aquarium seems to be mentioned a bit in some of the posts I've been reading of late. I just wondered what is best. Is it just high water turn over, or is it specifically good flow around stems/substrate level that helps? Whats the basic science behind it? On that note, I am due to setup a second external filter, doubling the turnover of water in my 180 litre tank. I wondered what positioning works best? Opposite ends, same ends, spray bars/single outlet? Thanks in advance Steve.