Introducing new fish to your home aquarium is one of the most exciting moments. Yet it is one of the moments when things can go seriously wrong. While putting fish into a fish tank might seem to be an easy task, one of the top reasons for new fish losses is from doing it wrong. Even when you have fully cycled your aquarium and you have everything else ready, you have to follow the instructions exactly when it comes to adding new fish.
Before we get started on how to introduce new fish, make sure your home aquarium is fully cycled before bringing any fish home at all. For more information please see the article on Aquarium Nitrogen Cycle.
What can go wrong during introducing new fish? Fish are fragile animals. They can’t regulate their body temperature like us. Large and sudden change in water temperature can seriously shock and even kill them. Amongst many other factors, such as the water hardness, PH, can also be deadly to them if the new environment does not come close to where they came from. To test the water, you will need specialized water test kit. My favorite test kits are API Freshwater Master Test Kit and API GH & KH Test Kit.
Most of the potential dangers mentioned earlier can be avoided if you give the fish enough time to slowly adapt to the new water. Most people in the fish keeping hobby use the term acclimate. It is a simple yet very important process which is mandatory each time when you introduce new fish to your home aquarium.
Three main steps to acclimate new fish
1. To acclimate fish to the new environment, we must first let the plastic bag which we used for bringing the fish home to sit in the fish tank water. It is to let the water temperature inside and outside the plastic bag get close to each other first. Alternatively, we can relocate the fish along with the water from their plastic bag to a plastic fish container. These little containers can be hung on the side of a fish tank. Just make sure it touches the water in the tank. Keep in mind that the water temperature does not have to be an exact match. Even as fragile as the tropical fish are, they can handle the sudden change of around 3~4F difference in water temperature no problem. Any larger difference in a sudden change scenario might shock them and even cause death.
2. Wait for about 15~20 minutes for the water temperature to get near the tank water temperature. Then add some water from the tank water into the plastic bag or the fish container. I usually add no more than 25% water to the water in the plastic bag. Any more than that might cause too big of a change in water PH, hardness amongst many other things for fish to handle.
Wait for another 15 minutes. Then dump some water from the fish container. I usually dump about 25% water. Make sure not to let the water from the fish container get into the fish tank. It might contain parasites and harmful bacteria. Just throw it away. Then add another 25% water from the fish tank into the fish container.
Another 15 minutes later, dump 25% water before adding 25% water from the fish tank.
Repeat the process until it is almost all tank water inside the fish container. By then, the fish should have adapted to the tank water, and you are ready to release them.
3. Release the fish into the fish tank by just let them swim out of the fish container on their own. Try to avoid scaring them. Let them settle in, explore the new home. You might want to observe them for a while to see if there is anything wrong after immediate release. Do not feed them right away. In fact, try to avoid feeding them for at least a few hours or the first day of introduction. Fish can handle starvation just fine as they do not need as much energy since they do not have body heat.
New fish might not feel comfortable enough with their new home to start their first meal. Give them some time. Rushing to feed the newly introduced fish might cause leftover fish food which will result in water pollution and ammonia poisoning. You might also overfeed them if you feed the new fish too early, as a few “outgoing” and starving fish might eat too much. It can cause them the digestive problem and even deaths.
And then? Just sit back and enjoy your aquarium fish! 😊
Keep in mind that, even with this acclimate process, some weak or sick fish might still not make it through the transaction. Some aquarium fish on the market are from poorly managed fish farms where overbreeding and antibiotics are common. Plus the stress they went through during the transportation. It is not uncommon that you might still lose a few fish out of dozens within a few days after the introduction. If you have done the acclimating process right, you can sleep well knowing it is not your fault.
On a side note, if you already have fish in your home aquarium, you might want to introduce the new fish to your quarantine tank first to avoid possible contagious fish parasites and diseases. This is another very important step to minimize fish loss.