So you've went out and bought some fish and the store told you to float the bag in the tank for 15 minutes and then release them into your aquarium. Right? Wrong! The only thing floating the bag accomplishes is that it brings the water in the bag closer to the temperature of the water in your tank. We need to be concerned about more than just temperature. The aquarium water chemistry is just as important as the temperature.

The Floating Bag Method
This is probably the most common acclimation method and it works well. You just need to be careful when floating a bag full of unknown water in your tank. Ideally, you're floating the bag in a previously setup quarantine tank but, sadly, many new hobbyists don't use a quarantine tank. After you've been in the hobby for awhile and experience any sort of fish disease outbreak you'll soon come to realize the importance of a simple quarantine tank.
After you leave the fish store you will want to go straight home to avoid ammonia accumulating in the bag (in the form of fish waste). Once you get home, open the top of the bag and remove about 25% of the water from the bag. Replace this water with the same amount of water from your tank. Float the bag in your tank and bring down the hood opening on the open end of the bag to help keep the bag secure. Every 10 minutes add about 1 measuring cup (use less if the bag is smaller) of your tank water to the bag. Repeat this process for about an hour. After an hour has passed use a small net to get the fish out of the bag and gently place the fish into your tank. The main idea here is to slowly get the fish used to your tank water (acclimated). Do not dump the bag water into your tank! If you do, you risk exposing your tank to any parasites or diseases that were in the dealer's tanks.

Some fish may be difficult to net while in the bag and you don't want to damage the fish while trying to net them. If you're having difficulty netting the fish, get a large bowl (large salad bowl works well) and carefully pour the bag water into the net, allowing the bowl to catch the water. You could bypass the bowl altogether and do it over a sink but make sure that the drain plug is in place just in case you miss the fish with the net.

By slowly adding small amounts of water from the tank we are slowly acclimating the fish.

The Bucket Method
This method is basically the same as the floating bag method, but instead of floating the bag in the tank you're putting the bag inside a clean bucket instead. The bucket method is better than the floating bag method because you don't have to worry about any of the bag water entering your tank.

Open the top of the bag and remove about 25% of the water from the bag. Replace this water with the same amount of water from your tank. Every 10 minutes add about 1 measuring cup of water to the bag. Repeat this process for about an hour. After an hour has passed use a small net to get the fish out of the bag and gently place the fish into your tank.

The Drip Method
The drip method is recommended for most saltwater fish and invertebrates because they can be more sensitive to pH, specific gravity and other water chemistry changes.

To do the drip method your going to need a bucket, a vegetable clip with a suction cup for holding the tube in the tank and a length of air pump tubing that is long enough to extend from your tank to the bucket. Place one end of the tube into the veggie clip and then place the veggie clip into your tank. Tie a knot in the tubing to regulate the amount of water flow coming out of your tank. Get the siphon going and place the other end of the tubing into the bag in the bucket. You'll want a slow drip, drip, drip going. Aim for drips every one to two seconds. If you're having troubles using the knot to regulate the drip rate, any type of strong clip should work. Vice-grips (locking pliers) or c-clamps would work as well.

How long you do the drip method depends on what your acclimating. If your doing this method for most freshwater species you should be ok doing it for an hour or so before introducing the fish to your tank. If you're doing this method on a saltwater invertebrate you may want to take 2 or 3 hours for this acclimation procedure. If you have a good pet shop and you trust their advice, ask for and follow their recommendations on the amount of time needed for acclimation.

Acclimating new fish to your aquarium is a critical step and should not be taken lightly. Getting into the habit of using proper acclimation methods is a good way to ensure your long-term success in this wonderful hobby! Check out the video below for more tips.

http://www.fishlore.com/acclimating-tropicalfish.htm