Can You Add Fish to a New Tank Right away?

You have bought a new aquarium along with all the equipment to make a beautiful aquascape. As soon as you get home, you are excited to immediately make the aquascape you have been dreaming of for a long time. Don’t forget you also directly buy fish that have long been wanted to be maintained and complete the aquascape. After a few days the fish in the aquarium did not look healthy, some even started to die. Do you know why the fish died?

The new aquarium does not yet have enough bacteria to break down waste from fish waste. Therefore, the aquarium is not stable and if it immediately receives a lot of fish waste that cannot be decomposed, it causes the water in the aquarium to be toxic to fish.

How long should I wait before adding fish to the aquarium?

You can wait at least a month for your aquarium to be completely full of bacteria that will break down toxic substances. The toxic substance is called ammonia, which when bacteria is present it will be broken down into nitrite and finally into nitrate which is less toxic to fish in small amounts. This is one of the important reasons why aquarium water must be changed regularly.

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This ammonia-degrading bacteria can grow in various places in your aquarium. If you make an aquascape, the bacteria can be in the rocks, sand, and even the glass of the aquarium itself. You of course also realize that the filter used must contain media for organic filters as well. It is also a place for these bacteria to grow and thrive. So don’t ever clean your filer with water other than the aquarium because it will remove the bacteria. In addition to bacteria, plants used in aquascapes also help to break down this ammonia.

How to speed up the growth of bacteria

Use used filters

As I said before, these ammonia-decomposing bacteria grow in various places. The easiest place to move is the filter. If you already have another aquarium that definitely contains bacteria, the filter in the aquarium can be moved and used in a new aquarium. In this way, the bacteria in the filter will be carried to the new aquarium, accelerating the growth of bacteria and making it easier for fish to be filled as well.

In addition to filters, you can also use water from other aquariums to fill a new aquarium. Of course, ammonia-decomposing bacteria are also present in the water, so using water from an old aquarium will remove bacteria as well. But I suggest don’t take all the water from your old aquarium, just a few percent to get started. I also recommend not immediately filling the tank with a lot of large fish because the bacteria present in the filter or water alone may not be enough to break down the large amount of ammonia.

Use resistant fish

If you have just finished your first aquascape and don’t have another aquarium, then the above method certainly can’t be done. But don’t worry because there are still several ways you can do it. That method is to add hardy fish , or in Indonesian, to add fish that are resistant to being placed in a rather harsh environment.

Usually these fish are small in stature such as guppies, moles, bettas, and zebra danio. Because the fish are small and are in a large aquarium, the effect of ammonia will not be felt by the fish too quickly. As with larger fish, it will be affected more quickly by the increase in ammonia. Later the fish will release a lot of dirt so that it will trigger the growth of natural ammonia-degrading bacteria.

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Use starter bacteria

The two methods above in my opinion are the easiest way to multiply bacteria instantly. Another way is usually to use a starter bacteria that you can buy in stores. Of course, these bacteria also need to eat to grow, so one other way that can also speed things up is to use fish food. Decomposing fish food will produce ammonia and at the same time become food for ammonia-decomposing bacteria.


Indeed, it feels impatient to add fish to the aquascape that you have worked so hard for. It also happens to me often, I can’t wait to buy fish and add them to the aquarium. However, you must understand that the growth of bacteria in the aquarium is important before adding fish.

If you are impatient, of course you can use a filter from an old aquarium and then add some strong fish such as guppies, moles, or zebra danio to then speed up the process of multiplying bacteria. Apart from this method, you can indeed use starter bacteria, but I personally have never used this method. Maybe this method is also effective, but I still recommend not adding large amounts of fish right away.