I have a planted tank - Sump - setup.. and I read how many people, replace their socks often - mainly because of overflow (water restriction), which makes sense. Then there are others who say that their parameters are affected by having their socks in there, for more than 2 days etc. I find this second reason - ridiculous, as I see the filter sock - doing nothing more than what a typical canister (external) filter would be doing. Can someone please explain to me, if there is any reason other then overflow, why a filter sock would need to be replaced more often, based on the reasons that it is affecting the parameters - we all know and love Ph, Ammonia, Nitrate and Nitrite? Thanks in advance. Please note that I have a planted aquariums x 2, 1 with an external canister, which gets briefly cleaned - once every 3 months, and I have never had any issues with the water or fish, and now recently I have a sump tank, which I have just installed a filter sock and learning all about sumps..