Seriously. Bring a bucket or cooler with you. Net the fish, toss em in the buckets and drain the tank. If you decide to leave the fish in the tank, pull all the decorations from the tank. I didn't with a 30 gallon I picked up and when I got home I noticed a rock fell on top of a baby pleco and killed him.
If you get home right away and no debris gets in the tank, you'll be able to fill it with water again and toss the fish back in. The filters bacteria will still be good to go.