Ok, I have an earlier post about plants for a tall tank I have set up and running. I have more or less decided on plants that I am going to have in the tank. This tank has been going strong for about 5 years now. I can drain the water out of the tank into a container, and perform a 20-30% water change when I do this. My question is should I drain the tank all the way down, remove the substrate (I can run my filter in my holding tank while I am changing the tank to planted) and put the new substrate and water back in without going through a full cycle? I have a placo and guppies in the tank right now, so I don't want to have the tank down for an extended period of time. I'm just wondering if I can do this.