I'm sure that everybody knows of the classic 'float the fish in a bag for a few minutes and then release him into the tank' method of acclimation. I've seen it in movies, cartoons, and referenced in many places. But, there is a little more to acclimating a fish to a new tank than meets the eye. Did you know that there are many different methods to choose from? This topic is actually one that causes much debate amongst hobbyists. Believe it or not some people get very defensive about acclimation methods and can get a little testy. Some have a specific method that they swear by and treat all others as if they cause the plague. Some hobbyist use a different method for different kinds of fish, while others use the same one no matter what they are adding.
Personally I tailer my acclimation to the needs of my fish, or whatever I happen to be adding to my tank. I tend to use the same methods that I use at work when acclimating fish to various systems. Which, incidentally, vary depending on what we are acclimating.
The important thing to consider is what is best for your fish and what materials you have to work with.
Why Float the Bag in the Tank?
So, what exactly are you doing when you float your fish in a bag at the surface of your tank? Are you even acclimating the fish at all? The short answer is yes. Floating the bag in the water does indeed acclimate your fish. But, it is not a complete acclimation. You are only getting your fish used to the temperature of the tank water. This is actually crucial to your fish's survival. A big change in temperatures and stress your fish, this stress could be the death of your fish. By allowing the bag to float in the tank for a period of time, say thirty to forty-five minutes, you are allowing the water in the bag to slowly heat up, or cool down to, the temperature of the water in your tank. Water has a very high specific heat, this means it does not change temperatures very quickly. Have you ever tried to quickly boil a pot of water on the stove? It takes time. Just like with boiling water it takes time for the water in the bag to reach the temperature of the water in the tank.
After floating the bag for a while many people simply release the fish into the tank. This method can be successful. However, this method does nothing to get your fish ready for the water quality of its new home. Also, many people often dump the entire bag of water into their tank. This is not a good idea since it adds water from the tanks at the pet store into your tank. Why is this bad? Have you ever noticed that the fish at the pet store don't always look that healthy? Well, by added the tank water that the unhealthy fish are in you could be introducing diseases to your healthy tank.
My recommendation is that if you are going to use the float in bag method that you should poke a couple holes in the bag after floating the bag for nearly a halt hour. This will allow for some of your tank water to enter the bag and allow the fish to slowly get used to the new water quality. This will also let some of the pet store water into your tank, but it is much less than what would be added if you just dumped the fish in.
Once you have allowed the bag to float for an adequate amount of time it is time to put your fish into its new home. Your fish should be behaving normally and should not appear to be sick. The easiest way I have found to do this is to cut the top of the bag off with a knife and use a net to gently remove the fish from the bag. Once the fish is out of the bag immediately place it into the tank and remove the bag before the pet store water is added to your tank.
The Drip Method
Many hobbyist are fans of the drip method. I must say that I also use this method with some of my more delicate additions, like my puffers for example. Essentially this method use requires a bucket and some airline tubing. What you are doing is slowly adding your tank water to the bucket with your fish in it, the fish start off in the bucket with the water from their tank at the pet store.
Some people swear by floating the bag in the tank before starting the drip method. They argue that you need to acclimate to the temperature first and then the new water quality. I disagree. As the water drips into the bucket it will slowly raise, or lower depending on the temperature of your tank water, the temperature of the water in the bucket.
I like to use an airstone attached to my airline tubing to anchor my airline in the tank, that way I don't have to worry about it coming out of the tank during the acclimation process. The trickiest part of this method is starting the siphon and tying the knot in the airline tubing. That's pretty much it. Tie the knot tighter if you want a slower drip and looser for a faster drip. It is as simple as that.
Once the bucket is mostly filled, over the course of around forty-five minutes to an hour, stop the drip by removing the airline tubing from your tank. Then use a net to move your fish from the bucket into the tank.
It is your choice if you want to stay and watch your fish while it acclimates. Acclimation, depending on the method you use, takes a lot of time. Not everyone has an hour or two in the day to sit and watch a fish in a bag or bucket. One advantage to watching the acclimation process is that you can see how your new fish is adapting to its new environment. I personally keep an eye on my fish, but I don't feel the need to sit and watch unless it is a particularly delicate fish.
A Combination Method
Some hobbyist like to use a combination method of the above mentioned two. It is rather simple and straight forward. Simply float the bags in your tank for roughly thirty minutes then open the top of the bag, careful not to let the bag roll over. Over another thirty minutes or so slowly add a little bit of tank water to the bag. Once you have added a sufficient amount of water, more than a 75-25 mixture, its time to add your fish. Some people just tip the bag over and let the fish swim out. Others use a net to fish the fish out of the bag and gently place it in the water. I advise strongly to use a net since you want to avoid getting the pet store tank water in your tank as much as possible.
One thing you do need to watch out for is the bag rolling over. After you have opened the bag the oxygen that had been keeping the bag floating will leave the bag. The bag usually stays at the surface, but it will not be as stable as it was when it was filled with air. This is definitely not a method that you can walk away from. Though, that can be a good thing since it will allow you to monitor your new fish closely. Then again if you are added more than one fish from separate bags this method might be a little difficult since you might need to hold up some of the bags.
Floating the Bag in the Tank
Acclimates the fish to the water temperature of your tank
Does nothing to acclimate the fish to the water quality of their new home
Floating the Bag and Slowly adding Tank Water
Acclimates fish to the temperature and water quality of their new tank
Can be messy, and often water from the pet story tanks gets added to your aquarium
Drip Into Bucket
Acclimates fish to temperature and water quality over a controlled period of time
Takes the most time and removes water from the system
Takes no time
Does not acclimate fish to temperature or water quality of their new tank. Causes stress for the fish
Varying Opinions on Different Acclimation Methods
As I mentioned earlier some hobbyist get very excited when talking about acclimation methods. This is because, like with many other things, they all think their methods and reasons are the best. Its almost like talking politics with someone. Some people have their opinion on things and that's all there is to it, and no amount of logic or facts is going to change their mind.
Some people swear by turning your lights off when you acclimate fish. They claim that you are going to heat up the fish your trying to acclimate, or the bacteria in the bag, too much and could end up introducing unwanted things into your tank. I don't buy it. If your lights do put off a lot of excess heat you can either turn them off or float the bag as far away from the lights as possible. Some people say that you should turn the lights off because it reduces stress on the fish. I would count this one as plausible since most fish tend to calm down in the dark since its easier for them to hide because they are less visible. At work we acclimate some fish with the lights on and some in the dark. How do we choose which fish get which treatment? Easy. Some fish are most sensitive and easily stressed than others. As a rule of thumb the more expensive a fish is the better care I take acclimating it. After all is it really worth potentially killing your $150 adult yellow tang when turning off the lights could possibly easy his stress during acclimation. Your call.
A lot of people get very upset when people don't use the drip method to acclimate their fish. Some people prefer to open the bags and slowly add tank water to the bags, or even just poke holes in the bag and let osmosis do its thing. Do both of these methods work? Yes. Will they have a higher risk of adding tank water from the pet store to your tank? Of course. Its rather funny, because you can set everything up just like you would for the drip method but pour water in cup by cup over a long period of time. The effect is the same. But some hobbyists don't understand that and will argue that its wrong until they are blue in the face.
Keep in mind there are a lot of opinions out there when it comes to acclimating fish. Some people site experience behind their reasoning others simply say its common sense. Some people pull things out of thin air and then go it for the rest of their lives. Remember sometimes its just luck. Some fish are just plain healthier than others and therefore they will have a better chance of surviving the acclimation processes.
Personally I base my decisions on academic knowledge, as my degree is in marine biology, and professional skills, as I work as an aquarist at an aquarium. I still have hobbyist tell me that I acclimate my fish wrong and that they are going to die, though so far I have not had any issues. Just don't take offense, they are only trying to help.
Things to Keep in Mind
In the end you can use whichever method you feel will work best for your fish and your tank. There are pros and cons to each method and as long as you are aware of that you will be fine. It is interesting how some downsides are obvious to some but not to others. One of my friends was using the drip method and it went horribly wrong. She has dogs and cats and she left her bucket on the floor. I'm sure you can see what happened. She simply didn't think about it. I personally always close a door if possible or remove as many potential disasters as I can. I would strongly advise letting the dog play outside, maybe putting that kitty in the bedroom for a few minutes, and letting children know not to touch the bucket. This will prevent, hopefully, the bucket from being knocked over, the fish getting stressed from things walking around the bucket, and pets from drinking from the bucket or even worse eating your new fish.
Hopefully with this advice in mind you will be able to safely acclimate your fish to their new home. I wish you luck with your new fishy friends. Home aquariums are truly a great source of entertainment and are beautiful additions to any home.
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
Alex (author) from Virginia Beach, VA on April 22, 2018:
Thanks! I think a lot of people are just so excited to put new fish in their tanks that they don't allow for a long enough acclimation period. Or they just really don't know that properly acclimating a fish will increase the chances of its survival in its new home.
Deborah Minter from U.S, California on April 14, 2018:
Good article! Sometimes the simple method of aclimation is tricky.