I want to do a full rescape of my 50 gallon, including mostly new substrate. However the tank is fully stocked. Can I remove about 75%of the substrate and replace it, or will this be problematic as far as bacteria goes? Also I'd prefer to empty most the water during the process to make things easier, maybe save some of the aquarium water in buckets while I'm working then partially refill with that water? I have a well established sunsun filter, will the bacteria survive in stagnant water the whole time I'm working? Thanks, any thoughts or advice would be appreciated.