Hey guys, I am cycling my 50 gallon fish tank right now. I was a dummy and added fish the next day after starting the tank. Anyways whats done is done and I added some old filter media from a friends tank and I am overloaded with water changes right now and other stuff. I had a quick question about doing my water changes...From what I know their is healthy bacteria growing in my substrate so would it be smart for me to just vacuum the very top layer of my gravel and not to the bottom of the tank as to not remove any of the beneficial bacteria?