When you go for your fish, take some Protozin with you and put a couple of drops into the bag before its tied up. When you get home, put the water and fish from the bag into a bucket adding another couple of drops of Protozin; add a cup of tankwater to the bucket every 5-10 minutes. Do that for an hour or until the bucket is nearly full - take your time. Since I started doing this, new additions have been problem-free. If you don't have a quarantine tank, the Protozin in the bag is the next best thing.