How to Acclimate Saltwater Fish and Invertebrates

When introducing your newly purchased inhabitants to your aquarium or quarantine tank, fish and invertebrates are introduced (or acclimated) in different ways. We acclimate saltwater inhabitants depending on their sensitivity to a change in environment. To ensure you do not harm them inadvertently follow the guidance below which I have been using for years.

Why do we need to acclimate saltwater fish and invertebrates?

When transferring saltwater inhabitants from one aquarium to another it is never as simple as floating a bag for 30 minutes and plopping them the tank. Each saltwater system can be completely different. Each could have differing nutrients levels such as phosphate and nitrate, or have higher or lower alkalinity and calcium. Most importantly, they may have a completely different salinity (salt concentration).

In fact, often saltwater fish are kept in ‘hyposalinity’ holding tanks or display tanks at your local stockist. Hyposalinity refers for a lower salt concentrations. A reef tank is normally maintained at a specific gravity of 1.023 – 1.025, but stockists display systems are regularly maintained at a specific gravity of 1.008 – 1.009. The reason they are kept at a lower salinity is that many fish parasites, including marine white spot, cannot tolerate it these levels. It is simply a method of parasite control.

It is worth knowing that invertebrates, corals, live rock and most other saltwater critters will die in hyposalinity. These will always be kept at about 1.025 at your LFS.

Acclimation is simply replacing the water they are accustomed to (in the fish bag) with water from your tank. We need to acclimate saltwater fish and invertebrates by introducing them to their new home in a controlled manner as described below. 

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The best way to acclimate saltwater fish

Saltwater fish can be very sensitive to their surroundings and are incredibly aware of what is happening around them, unlike most freshwater fish which remain oblivious to what is happening to them. For this reason some species can become pretty stressed out by the whole situation. If possible to reduce the stress it is always a good idea to move slowly around them, and even darken the room.

Acclimating saltwater fish should take no longer than 45 minutes. I have found the best way to do so is to work out how much water needs replacing, and replace it at 6 minute intervals at a rate of 40% at a time.

saltwater acclimation
A pair of Royal Grammas going into QT

For example, if your fish are transported in a bag containing 35oz or 1 litre of water, you should be aiming to add 14oz or 400ml every 6 minutes. Once you have topped it up 3 times, siphon the same amount out, then continue to do the same for up to 45 minutes. You should only need to top up a maximum of 8 times, discarding the same amount of water you add. If there was any salinity difference your fish will now be accustomed to the water in your tank.

While acclimating saltwater fish it is best to hang them in a pitcher (as above) or in the fish bag in your tank to maintain a constant temperature.  

Acclimating in a pitcher or fish bag may not always be possible. You may have bought many fish or one large one. If they are all from the same source tank you can add them to a pail or bucket with a low wattage heater to maintain a constant temperature as you acclimate them.

To make acclimation even easier, consider purchasing the Innovative Marine Accudrip, with a suggested drip rate for many types of marine fish and inverts.

The best way to acclimate saltwater invertebrates

Invertebrates are far more sensitive to changes in water than fish are. For this reason it is of utmost importance to take your time when acclimating them.

The method used for invertebrates is called ‘drip acclimation’. Invertebrates such as snails, hermit crabs, shrimps and starfish need to have your tank water introduced to their fish bag in a slow and controlled manner to prevent unwanted mortality.

In theory you could add the water manually as you would do for your fish, but given the time it takes (double that of fish acclimation) and the small additions of water it makes sense to drip tank water into the invertebrates water instead.

What is drip acclimation?

Drip acclimation is a process that slowly allows your invertebrates to adjust to the parameters of the new tank they will be living in.   Every tank differs slightly but even the smallest change might be enough to kill off these sensitive creatures. 

how to drip acclimate saltwater invertebrates
Drip acclimation of invertebrates

How do I set up drip acclimation?

You don’t need much in the way of setting up drip acclimation. 

You will however need:

  • A pitcher or pail depending on the need.
  • A length of airline usually used in freshwater aquariums (with or without an air control valve)
  • A couple of clothes pegs


Step 1

You will first need to float the bag of invertebrates to allow the fish bag water to adjust to the temperature of the new tank.  This can be done in the display tank, sump or quarantine tank, if that is where they’re going.  Float the bag for around 20 minutes.

Step 2

You can either place the bag into the pitcher for support or empty the water from the fish bag into the pitcher and place the inverts directly in. It is completely up to you. Place the pitcher as close to the tank as you can but at a lower level than the water surface. You can use a stool to put the pitcher on if your airline hose won’t reach as far as the floor. 

You will need to start by pouring out some of the water that came in the bag. This will create the space to fill with tank water.

Step 3

Use the airline to start a siphon from the tank to the pitcher.  You will need to suck on the end of the airline tubing to get a siphon flowing. If using an air control valve, set this so that there are approximately 1 – 2 drips per second going into the pitcher. You can turn it up a notch if you are using a pail.  If you don’t have an air control valve then simply tie a not in the airline hose and adjust accordingly.

You can use a clothes peg to keep the airline secured to the main tank. 

Step 4

As you would do when acclimating fish, when the pitcher is almost full, discard about 1/3 of the water and continue adding water with the airline. Continue to fill the pitcher or pail, discarding water as needed.

After approximately an hour and a half, your new invertebrates should be sufficiently acclimated. You will have replaced the fish bag water almost completely with tank water.

Of course, their is always an easier way of doing things, like using the Innovative Marine Accudrip.

Innovative Marine Accudrip Acclimator
  • Customize acclimation rates for any new additional into your aquarium
  • 1-2 Drips per second - for snails, shrimps, crabs, starfish, anemones

Drip acclimation and temperature drop

Depending on the temperature of the room your tank is in, the temperature of the water in the pitcher can either rise or fall significantly during the acclimation process.  Because the acclimation container will usually be smaller than the saltwater aquarium, and the process is only temporary, care will need to be taken to ensure that these fluctuations are monitored. 

One of the reasons I like to use a pitcher instead of a pail, is because once I have completed the drip acclimation process, I can hook the handle over the side of the tank and allow the temperature to readjust to the temperature in the tank. 

If you’ve used the bag to acclimate your invertebrates in, then you can simply float it until the temperature matches that of the tank.

acclimate saltwater

So there you have it...

I cannot understate how important it is to acclimate saltwater inhabitants correctly. Having gone to the effort of investing in these amazing animals, the last thing you need is to have the incorrect method of introduction kill them.

If you take your time and do it methodically, you will be ensuring you have done what you can to eliminate the potential for mortality.

How to Acclimate Saltwater Fish and Invertebrates