How Long To Let Fish Acclimate To New Tank | Aquascape Addiction

How Long To Let Fish Acclimate To New Tank

We cover the popular question of how long to let fish acclimate to new tanks? it seems to be a common confusion so we decided to cover the subject in detail to help you out.

How Long To Let Fish Acclimate To New Tank

Fish cannot just be dumped into a new aquarium and expected to be happy, let alone to survive. One of the most important things to do when buying a new fish is to let it acclimate to its new habitat.

How long to let fish acclimate to new tank is a hot button topic in the fish keeping world. Let’s get to the bottom of this issue and find out how long it takes for fish to acclimate to a new tank.

So, How Long Does It Take for fish to acclimate to a new tank?

One of the most common misconceptions and false pieces of advice given by amateurs is that it only takes around 15 minutes for fish to acclimate to a new tank. They will tell you to float the bag of water with the fish in it in the tank until the water reaches the same temperature inside of the bag as in the tank.

Yes, this is partially true, but there are a couple more steps involved and it certainly takes more than 15 minutes. Ideally, you should take at least one whole hour to let your new fish acclimate to their new environment. This can take even longer for larger fish.

Acclimating Your Fish – Step By Step

The best thing we can do for you here is to provide you with a step by step guide on acclimating your fish to its new home, so let’s do that right now.

  1. When you buy your new fish, get it home as soon as possible. Don’t dilly dally or go shopping in between. GO right from the pet store to your home. The water in a plastic bag is not ideal for long term living, it doesn’t have much oxygen, and fish don’t like being in plastic bags.

  2. Rinse the exterior of the bag off.

  3. Pour out the excess water in the bag, but leave enough to cover the dorsal fin totally.

  4. Place the bag into the aquarium. Keep the bag open and leave it folded back at the top so it can float in the aquarium without sinking, and so that oxygen can get to your fish.

  5. After 10 minutes of the bag floating in the water, add some of the aquarium water into the bag. You should be tripling the volume of water in the bag within an hour, using only aquarium water to do this.

  6. You should add a little more water from the aquarium to the bag about every 5 minutes. Do this for about an hour and the temperature inside of the bag should be the same as the water temperature in the aquarium.

  7. Once you have done this, you can introduce the fish into the aquarium without the bag.

Why Acclimate Your Fish?

There are several important things that come along with the acclimating process. Like we said, you can’t just dump the fish into the water. Up above, our main concern was the temperature, but there are other factors at play here as well.

  • All fish need certain water parameters. Of course, all fish are different, so you do need to make sure that the aquarium you have contains the proper water for the fish. If you already have other fish in the tank, you need to make sure that both fish can survive in the same water.

  • Slowly adding water into the bag not only helps with temperature, but it also helps the new fish slowly get used to the water’s acidity level (pH), the hardness, and the amount of other compounds in the water. You should ideally have the tank at the proper parameters before inserting the fish.

  • Fish are not always friendly and if you have a pre-existing community, they might not be happy about a new fish which they will perceive as an intruder. Putting them in the aquarium in the bag will give the fish a chance to get used to each other, and worst comes to worst, at least there is a barrier in between them.

  • Fish are also not a huge fan of noise. Filters and waterfalls can be a little disturbing to them. The plastic bag will provide a bit of a sound barrier. It will provide enough of a barrier to muffle a good deal of sound, but lets enough sound through to slowly get your fish used to the new sounds.


Remember folks, never just dump a new fish directly into the tank. This can create a lot of stress for your new fish and for the old ones too. If you don’t go through a proper acclimatization process, you may actually end up killing your new pet, so please be careful, be patient, and definitely follow the steps we have outlined above.