Most of us have practiced the age old method of acclimating our new specimens by floating the bag in the tank, pouring in a little bit of water a few times over a half hour, then scooping out the occupants and plopping them into our tank. Most pet stores will give you these exact instructions. The only time you hear anything different is when your newly purchased animal is particularly sensitive. Only then do we hear about drip acclimation. Why should we not use drip acclimation for every new inhabitant? In my experience, drip acclimation is safer, healthier, and much less stressful on your new specimens, allowing them to explore the tank, unafraid, much sooner.
Drip acclimation is a relatively simple process. The idea is that you acclimate your new inhabitants to the water chemistry of your tank, just like you would with the floating bag method, except it's over a longer period of time with a slower and more consistent addition of tank water.
The first thing you'll need is a 5 gallon bucket. The dark and calm environment inside a bucket is much less stressful for your new specimens than a floating bag which is exposed to the activity and the light of the tank and the room around it. If you are only acclimating a couple of small, aggressive species with limited water in the bag, you can use 2.5 gallon buckets. Next, you'll need a length of airline tubing, enough to extend about 6 inches below your tank's water level and then down into the bucket with about 12 inches extra. You'll also need an airline valve attached about halfway along the airline tubing, Finally, you'll need two 6 inch pieces of plastic moldable wire ( I use plastic paper clips). Do not use metal, as it will leach into saltwater.
After you bring your new inhabitants home, gently pour them and their water into the 5 gallon bucket. Fish and invertebrates from the same tank can go in the bucket together as long as they are not aggressive. Separate buckets for aggressive fish. Next, straighten the plastic wire and coil it around one end of the airline tubing with about 6 to 12 inches sticking out. Then, bend the airline tubing and coiled wire over the tank frame so it forms a U-shape with one end submerged in your tank water and the rest of the tubing leading down the outside of your tank to the bucket. Really, any method of attaching the tubing to your tank can work. I use a suction cup and bracket clip in the photo to the left, but the plastic wire is easy and usually handy. Next, cut the tubing and insert the valve some where in-between the highest point (the top bend), and the top of the bucket. Now coil the second wire around the bucket-end of the airline tubing, far enough up so that it bends over the top of the bucket and only enough tubing extends into the bucket so it is not submerged. This will create surface agitation from the drops of water, allowing oxygen exchange while acclimating.
Finally, you can open the valve and pull water from the bottom of the tubing until it starts to siphon. It's okay if the tubing loops below the top of the bucket as shown in the photo to the right, the water will still siphon effectively. Then close the valve just enough so you reach about 1 - 2 drips per second. Acclimate until you've added an equivalent amount of tank water as the bag water you started with, or for 45 minutes to 1 hour for more sensitive species. Don't worry about temperature fluctuations, the bucket water will reach close to tank temperature as it drips. Just keep the bucket away from air vents and direct sunlight. Finally, net out your new inhabitants and place them in the aquarium. Don't forget to dim the lights in the tank for a couple hours after you add them.
Drip acclimation is all around a less stressful process for your new fish and inverts. They have more time to acclimate. They are not bothered by the activity of the tank and room. Some species, like starfish, must be drip acclimated no matter what, but I believe all species benefit and so will you.
Photos
https://pixahive.com/photo/plastic-fish-bag-for-sale-at-a-shop/