It probably won't clear up real quickly, but your fish will be fine in a bucket over night. Trust me, been there, done that. Drain about half the water into the bucket, and scoop the fish in, and take out the bio wheel, and add that into the bucket as weel. Finish draining the tank, and take out your old gravel. It's a bit to large for this, and will make ur tank look smaller, and give your plants a hard time rooting. Then rinse your bag of flourite, and let it dry. (you could probably do this before you even start, to make the transistion faster and eaiser). Put the flourite into the tank, and very very carefully, add water to the tank. It woudl be best to gently scoop it up with a margarine container, into the tank,a nd gently pour it onto a plate, or a piece of plastic lying on the bottom of the tank, fill it about 2/3 with original water, and add some top off of clean water and let the filter do it's job. With any luck, it won't be a total mess, and your fish can go in, within a few hours, if not the next day.