Acclimating from a bag
Float the bag at the top of the fish tank. Before you do this, make sure the bag has enough air so the betta can breathe. Letting the bag float at the top of the betta’s new tank will allow the water in the bag (with the betta in it) to match the temperature of the water in the tank.
This process is known as “floating” the betta.
Let the bag sit in the tank for 10–15 minutes.
Mix the water from the tank with the water in the bag.
Once the bag has floated in the fish tank for about 15 minutes, you can start to expose your betta to the water in the fish tank. Use scissors to cut a hole in the bag. Using a baster or a small cup, pour about a cup of the tank water into the bag.
You’ll need to stand there and hold the bag upright during this time. If you release the bag or let it tilt too far to one side or the other, the water will spill out into the tank.
Let the water sit for 15 minutes.
Your betta needs this time to slowly adjust to the temperature, pH level, and mineral hardness of the water in the tank. If you rush these steps and do not give your betta time to acclimate to the water, it will be harmful to the fish’s health.
Repeat the step one more time: mix another cup of tank water into the bag with the betta.
Continue to hold the bag in the tank during this time. Make sure to keep the cut in the bag facing upright.
Release the betta into the fish tank.
After acclimating the fish for roughly 30 minutes, take the bag, turn it sideways, and allow the betta to swim out. Your betta may take some time to get used its new surroundings, but it should be comfortable living in the water of its new tank at this point.
If the water in the betta’s bag is dirty, minimize the amount that gets into the fish tank. Dirty water in your tank is never a good thing!
After the fish has been acclimated, you can also take an aquarium net and gently place your betta in the tank.
Do not feed your betta right away. The fish will probably not eat for the first day it’s in a new tank. Some bettas will refuse to eat for the first three days, sometimes even a week.
Acclimating from a Cup
Float the cup containing your betta at the top of its new fish tank.
At this stage, you want your betta to get used to the water and its temperature. A sudden exposure to the (probably colder) water of the fish tank would be harmful to your betta.
Let the cup float for about 15 minutes.
Pour some of the tank water into the cup.
Do this slowly, using a baster or a small cup. (Do not pour the tank water directly onto the betta; pour the water off to the side of the fish) At this point, the cup should still be floating in the fish-tank water.
The betta needs to get used to some of the tank water, as it will have a different mineral hardness and pH level, in addition to a different temperature.
Leave this to sit for 15 minutes.
Add a little bit more of the tank water.
You want the tank water and water from the cup to be very well mixed—almost at a 1:1 ratio—before you place the betta fish in the tank. Again, wait for 15 more minutes.
At this point, you can use your fingers to feel the temperature of the fish-tank water and the cup water. They should be roughly the same temperature.
Transfer your betta from the cup to the fish tank.
Using an aquarium net, gently take your betta out of its cup and move it into its new tank. Be gentle, as you do not want to poke or harm your new fish.
If the water in the betta’s cup is relatively clean of excrement and silt, you can pour the fish and its water directly into the tank.