Can New Gravel Kill Fish?

The purpose of having new gravel in your fish tank can be either to replace the old ones or just for aesthetic purposes. But the gravel replacement is very tricky because some beneficial bacteria live there.

This is why many people keep on asking in many forum sites how they will get new gravel without killing the fish and other microorganisms in there.

Can new gravel kill fish? No, it won’t affect the fish as long as it’s done correctly. Cleaning new aquarium gravel is an important step in keeping your water quality to a higher level. If you didn’t do it correctly, gravel dust and residue could harm or even kill your fish.

In this article, you will find some useful tips that will help you clean and get a new set of gravel for your fish tank. It is important to do this correctly to avoid the worst-case scenario – killing your fish.

Temporary Setup

When it comes to replacing your old gravel with the new ones, there is one way to fo a complete gravel removal without harming your fish. This is by setting up another tank for the new substrate.

It just means that you are running a fishless cycle on a separate tank full of gravel. Additionally, you need a filter and ammonia to start up the cycle and dose it occasionally.

Seeding Gravel

Another way to be able to get a new set of gravel is by seeding gravel. You only need some pantyhose or filter media bags and fill them to the brim with the new gravel.

You can place these sacks in the aquarium, thoroughly rinsing them properly. You see, after a month, you can remove the old gravel and pour in the new rinsed gravel along with the cultured ones in your fish tank.

This process is actually pretty cheap compared to the ones where you have to build a separate tank.

The downside is that you are only colonizing a small part of your new gravel.

Colonizing at least half of the gravel is the required amount, but this would mean overcrowding your tanks with different bags of gravel.

Replacing Sections

This is probably one of the most popular choices in changing your old gravel to new ones.

There are many videos online using dividers for tanks, such as betta dividers, to separate the gravel.

This way, you can separate one portion at a time, and you have most of the gravel’s beneficial bacteria throughout the process.

Different chain pet stores and local fish stores have these dividers, but it is cheaper to make your very own.

You only need to have some plastic mesh found in any crafts stores, suction cups, and some plastic needles. Just ensure that the top of the divider is smooth, so it does not catch any fins.


No matter which method you actually use, be sure not to take out any filter media during this process, even the chemical ones.

It is recommended to wait at least 2 weeks after partially changing the media to begin this procedure.

Replacing new gravel won’t kill your fish as long as you follow the above procedure. These procedures will assure you of replacing gravels properly.