Acclimation is the process where you introduce a fish, coral, or invertebrate to new water conditions without causing shock that would harm the animal.

If you remove a fish from a tank where the water is maintained at 74 degrees, and place it in a tank with 78 degree water, the fish will die from shock.  However, if you gradually introduce warmer water – by “floating the bag” for freshwater, or drip acclimation, which we’ll discuss shortly – the fish will not suffer, and will be matched to the conditions of the new tank.

There are many variations to the acclimation method, but the goal is the same: slowly introduce the animal to water conditions from the new system. For freshwater community fish, you can simply place the store bag, still sealed, in your tank and let it float.  Depending on the temperature difference, it should take 15-30 minutes for the bag’s temperature to equal your tank’s water temperature.  Once this is done, the fish can be added to your tank, but don’t pour the bag’s contents into your tank; pour the bag through a net into a sink, then put the netted fish in the tank.

 The Floating Bag Method only acclimates for water temperature.  With sensitive freshwater fish, and all saltwater animals, you have to consider the other parameters that affect them. Things like pH, kH, salinity (for saltwater and brackish fish), nitrates, levels of trace elements like iodine and magnesium, these are all water parameters that can affect the health of your newly acclimated fish.  It seems intimidating, at first, to think that you can match all these water parameters perfectly for your fish.  But it’s not difficult at all, if you follow our instructions for the Drip Acclimation Method.

Drip acclimation requires two items: a length of air hose tubing, and a container to hold your new fish (for the sake of brevity, we’ll talk about acclimating fish, though this also applies to invertebrates and corals).

Place your new fish and the water from the bag into your container.  Anything about a gallon in size is good; if it’s a big fish, bigger than six inches, use a five gallon bucket.  Don’t “fill the container with fish” – make sure there’s room for it to be comfortable, so it can at least turn around.  You want enough water in the container so that it covers the fish’s fin, and a bit more.  For example, anything damsel/dottyback/blenny sized would need less than 2 inches of water; a big yellow tang might need five or six inches.

Take the air hose tubing, and clip one end into your tank.  If you have a cleaning magnet, this makes a great clamp.  Place the container with fish next to the tank, then start a siphon by sucking briefly on the air hose.  You should get a nice stream of water into your container.  This, however, is too fast; it needs to be a drip.  Tie a pretzel-knot in the air hose line, and slowly pull it tight.  You’re waiting for the stream to change to a fast drip.  Don’t let it drip too slow, or the water will cool too rapidly.

The rate of the drip should cause the water level to double in about fifteen minutes.  When this happens, pause the drip and pour out half of the water.  Now your container holds 50% old and 50% new water! Continue the drip.  Each time you do this, you’re reducing the old water by 50% – next time it’s 25% old water, then 12.5%, etc – so after five times, you have reduced the “old” water in the container to less than 10%.  At this point, verify the water is the same by comparing salinity using a hydrometer (skip this, obviously for freshwater), net your new fish and introduce him to his home.

There are, of course, variations on this basic method. If you’re acclimating shrimp, it’s important to take plenty of time, and you should run a slower drip (just make sure the water temperature doesn’t drop too much).  With hardy little hermit crabs, you can speed things up quite a bit and do five minute drip sessions instead of fifteen.  For the freshwater aquarists, we recommend that you drip acclimate any fragile fish like farlowella cats, small angels and many eels, as well as any large or expensive fish.  Honestly, the only fish we consider safe for floating bag acclimation are the small community fish – mollies, platys, tetras, guppies.

Acclimation shock is likely the biggest killer of new aquatic animals.  If you take your time and acclimate your new fish properly, they will stand a much better chance for survival.  It’s helpful, after introducing a new fish to your tank, to turn off the lights for the remainder of the day to reduce stress.  Also, don’t drop the new guy in the top of the tank.  Most fish are trained by their owners that whatever hits the top of the tank is food.  Instead, take the netted fish and lower the net to the bottom of the tank for release, preferably near a hiding spot.  This gives your fish a chance to find a place to hide, while avoiding the “bite first” mentality that comes with putting something new in the tank.

Finally, remember that if you have any questions, or if you are unsure of the acclimation method, don’t hesitate to contact us.  We want to do everything we can to promote healthy, happy fish.