Introduce New Fish to Their Tanks - as part of the expert series by GeoBeats. Hi, I am Steve Lundblad, owner of The Wet Spot Tropical Fish located in northeast Portland. When purchasing new fish for your aquarium, one of the best ways to introduce those fish into your new tank is when you first get home, the best thing is to float the bag in your tank. This will depend a lot on how cold the bag is got on the way home. Could be if it is cooled down a lot you may want to float that bag for anywhere from 10 to half an hour depending again on how cold it is. Secondly, you are going to want to open up that bag, add some water to the bag to acclimate for ph and water chemistry. Again this could vary depending on how much different your water is than the water of the fish you purchased. And then another really important factor is if you are buying very aggressive fish, when you get those fish home and you have done those first two steps and you release them into your aquarium, be sure that they have a place to go because a lot of very aggressive fish will see the new comer as a basically something to go after. So, you need to be sure that the tank has been rearranged a little bit so he has a place to go so he does not get immediately harassed by all of the fish in the aquarium. And these should definitely make the introduction of the new fish in your aquarium easy and not too hard to do.