After the run-in period, it is now time to let the first animals move into the aquarium. But here, too, you should be patient and not put all the inhabitants into the aquarium at once. The reason for this is that the beneficial bacteria can get used to the fish and adapt better.

Before you go to the dealer you trust, you should check the water values again. You must pay attention to the toxic substances in the water and to values such as the total hardness, the pH value, …
These should correspond with requirements of the planned fish. If this is the case, nothing stands in the way of the first fish purchase.

In the store, you should make sure that the fish look healthy, do not have rapid breathing or any other strange behavior. It is also worth looking more closely into the aquariums. If there are several dead fish in the aquariums, it is better to buy the animals in another store. If the conditions in the store are bad, it can happen that you get diseases with the new fish in the aquarium. Also it can be the case with weak animals that they do not survive the relocation stress.

If everything is in order and you are about to buy the fish, you should already know exactly how many you need and with what sex. Many fish need a school to feel comfortable. Others need only one partner and prefer to be all alone. With many species you should only buy one male to several females. However, with another species this may be different. One should also be aware with the sex that males and females can have babies.

After you have thought about all this and you have bought the animals, you usually get them in a plastic bag or something similar. When you arrive home with it, you should not simply dump it into the aquarium, because the animals must first be slowly accustomed to the water values at home. To do this, turn the bag upside down a few times and ideally still attach to the edge of the aquarium with a clamp, so that the bag is under water. This allows the water in the bag to take on the same temperature as that in the aquarium. In the further course you add a little bit of aquarium water into the bag every 15-20 min, so that in 1-2 hours at least 50% of the water is aquarium water. For shrimps it is recommended to make this process even more gentle. In this case, you should perform the procedure for at least 2-3 hours.

Now to put the fish or other animals into the aquarium, there are several possibilities. Either you catch the animals with the landing net or with your hand out of the bag and then put them into the water or you put the contents of the bag into an extra bowl and then use the landing net or your hand again.

So that the animals are not so stressed, it is recommended to turn off the lights and not to feed that day.