Most living organisms are vulnerable to abrupt changes in their environment, so any changes must be made gradually. It’s the equivalent of stepping out of a lovely air-conditioned building straight out into a hot summer’s day at 120° F. The sudden change can be a shock until you get used to it. The same principle applies to your fish, except that a slight change in just one water parameter might be enough to kill them.

Fish acclimation is a gradual process of equalizing water parameters between two containers in order to prevent any abrupt changes causing illness or even killing your fish. There are two methods you can use to acclimate your fish, either the Floating Method or the Drip Method. They’re both very easy to complete, with high survival rates. 

Moving fish from one source of water to another is a simple but very important process that has been perfected by thousands of aquarists over the decades. In this blog, we will provide a step-by-step guide for each method to ensure you successfully acclimatize your new additions without a hitch!

Is Fish Acclimation Necessary?

Fish are sensitive to rapid changes in pH, temperature, salinity, ammonia, and nitrates. When you buy a new fish from an online retailer, a local fish shop or another aquarist, the chances of their water matching your aquarium water are very small. Many fish stores like to keep the salinity level on their tanks much lower, to prevent disease spreading throughout the system and killing their stocks. Shipping is very stressful for fish and this stress can bring out hidden diseases or cause a sudden illness, which can wipe out an entire established aquarium.

NOTE: Any new purchase should ALWAYS be quarantined to protect your aquarium!

Do Fish Need To Be Quarantined First?

Quarantine is the method of putting any fresh or sick/injured/harassed fish in a separate aquarium. This also applies to new fish. By separating fish out of your main tank, they can be easily medicated or examined to ensure that illness does not spread throughout your main aquarium. Six weeks is a normal quarantine time. You can set up a simple quarantine tank for less than $100, and it will save you from having to deal with an aggressive disease that could kill your entire tank.

Acclimation needs to be done when fish are going into quarantine as well as when fish are going from quarantine back into your main display tank. Remember, anytime you are moving a fish from one tank to another, you must acclimate them!

How Long Do You Need To Acclimate Fish For? 

Acclimation should take a minimum of 30 minutes to 1 hour and should definitely not be rushed. Patience, patience, patience. This is an important and worthwhile step, that if not done right can be costly. 

First Step to Acclimatization For New Fish

You must prepare a few things before you begin acclimating your new fish. Simple things that can help greatly reduce stress for your fish include:

  • Turn off the lights on the main display tank or your quarantine tank and dim the room lights.
  • Do not have bright light aimed directly into the transport box.
  • Carefully open one side of the transport box to allow a small amount of light in. Leave for 5 minutes.
  • Slowly open the box over the next 5-10 minutes to fully acclimate the fish to the light of the room.

Method 1: Floating Method

  1. Get a clean cloth and a cup of aquarium water and clean the outside of the transport bags to remove any surface oils or dirt.
  2. Keep the bag sealed and place them in the aquarium to float for 15 minutes. This allows the temperature of the water in the shipping bag to slowly adjust to the aquarium water’s temperature. Do not open the shipping bag.
  3. After 15 minutes carefully cut open the transport bags at the top. Roll the top of the bag opening down like a sock approx 1″ and fix/peg them to the rim of the aquarium. This will prevent any of the transport water escaping into your tank.
  4. Get a small jug and add 1/2 cup of your aquarium water into the transport bag.
  5. Repeat this process every 5 minutes until the shipping bag is full.
  6. When the bag is full, use the jug to remove 50% of the transport bag’s water and dispose of it down the drain.
  7. Repeat steps 4-6 for around 30-50 minutes.
  8. Use the net to remove the fish from the transport bag and slowly place the fish into your aquarium.
  9. Carefully remove the transport bag from the aquarium and dispose of it.


Method 2: Drip Method 

This approach is considered to be more advanced. It is typically targeted at vulnerable inhabitants, such as corals, shrimps, starfish, and wrasses. 

  1. Get a bucket or container and ensure it is thoroughly washed and rinsed.
  2. Use the scissors to cut all the transport bags and empty all the water and fish from the transport bags into the bucket.
  3. Use a clothes peg to secure an airline hose to the rim of your aquarium.
  4. Tie a loose knot into the airline, then suck on the hose end nearest the bucket to start the flow of water from the aquarium.
  5. The tightness of the knot will set the drip rate. Aim for 2-4 drips per second. The looser the knot = the faster the drip rate.
  6. Allow the water height in the bucket to double, then remove 50% of the water and dispose of it.
  7. Repeat step 6 for 40-60 minutes.
  8. Use the net to remove the fish from the bucket and slowly place them into your aquarium.
  9. Dispose of the water in the bucket.

Remember, always follow the acclimation procedure even if your new arrival appears to be dead. Some fish and invertebrates can appear as though they are dead when they arrive and will usually revive when the above procedure is followed correctly.