Posted by: nyaquatic | January 12, 2010

Acclimating New Fish to Your Tank

One of the most common questions and debates asked by  new and experinced hobbyists is the best way to acclimate new fish into an established tank, There are sevel tried and true method.

Earlier today Jimmy D wrote

“IMO a slow drip acclimation is the BEST and ONLY way to acclimate fish and inverts. I drip 1-2 drops per second until I’ve doubled the amount of water the specimen came in. then I’ll dump 1/2 out and repeat the dripping. this time at a rate of 4-5 drops per second. dump again when you’ve doubled the amount again.repeat until you’ve done this 4 times. this way you should’ve, in theory,replaced all the water the specimen was shipped in with your tanks water. It takes time and patience, but works the best in my experience. I use a 5 gallon bucket (exclusively for aquarium use) and typically take upwards of 2 hours for the entire process. I hope this helps, and enjoy a WONDERFUL hobby! “

I would like to add a couple of cautions.

Typical acclimation should take 1 1/2-2 hours.
It is rarely advisible to acclimate longer than 2 hours.

People often make the mistake of seeing a fish that initially looks good, then starts to go down hill. They extend the acclimation longer and longer thinking the fish will come around. Most of the time, the fish are being acclimated without a heater or an airstone, so the water in the acclimation tank is getting cold and depleted of oxygen. This is especially true if you are acclimating several fish in the same bucket.

Please pass along your own tips you would like to share.




  1. It’s actually for that reason I DON’T use slow drip acclimation in the winter. Here in the Northeast my house is never 80 in February. I prefer to float the bag (clipped to the lip) and systematically remove some water from the bag (about 1/2 cup) and replace with aquarium water. I do this every 5 minutes for 1 to 1.5 hours (depending how delicate the animal). I actually have a 5 minute timer so I don’t forget. This way the temperature is never an issue. Hey, has always worked for me.

    • Thanks for the comments.
      The only problem with that, IMO, is that it counts on the human to stay focused on acclimation for a long time.
      The drip allows one to set and forget, at least for a while.
      But your method is certainly great, IF you stay on top of it.

      Welcome to the blog!

      • That’s true, you don’t want to be wondering off. 😉 With the cost of fish, these days, I tend to make acclimation a priority.

  2. I use a slight variation. Since my systems run with fairly large refugiums, I float the bag in the refugium for about a half hour. Then I cut a half inch slit in the bag, and start a drip line from the DT with a tiny ball valve on the end of it. Grab the bag at the top, and hold the slit with other hand, done in about and hour and a half start to finish.

  3. to Michael’s point, I use the float the bag and add water from tank method and works great, I would only caution the bag process with larger fish, I once clipped a bag and walked away for a few minutes only to find the fish was squished by the bag and quickly suffocated, what an awful day that was!

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