New driftwood in the aquarium: why does the water remain cloudy despite water changes?

The question comes up often at the counter: you restart a freshwater aquarium, install a beautiful branch bought in a store, and the water refuses to clear. You change part of the water, it becomes clear again for a day, then the haze returns. In the vast majority of cases, neither the wood nor the aquarium is “a failure”: the wood releases natural substances, and an aquarium being restarted goes through a phase of bacterial imbalance that repeated water changes prolong rather than shorten. The key is to determine which of these two situations you are observing, because they are not treated in the same way.

Three different types of cloudiness behind the same word “opaque”

The word “opaque” covers very different realities. Before buying anything, fill a transparent glass with aquarium water and look at it in front of a white sheet in daylight. This simple test guides everything that follows.

Often, two causes overlap: wood that slightly colors the water and a restarted aquarium undergoing a bacterial bloom. The eye then sees “dirty” water without being able to say why.

Wood, a natural source of tannins

The roots and branches sold for aquariums are hardwoods, often sourced from mangroves or rivers. They contain tannins and humic substances, the same compounds that give forest streams and peatland waters their tea-like color. In an aquarium, these substances slowly diffuse into the water for weeks, and sometimes months for larger pieces.

This is not pollution. In soft, low-mineral water, these compounds can lower the pH slightly, and many tropical river fish naturally live in this type of amber-colored water. The problem is mainly aesthetic. Unprepared wood taken straight out of the bag, however, releases much more color at first, which is what comes as a surprise.

Changing the water does not solve the discoloration: the wood continues to release tannins, and each water change only dilutes them temporarily. You must either prepare the wood or remove the tannins as they are released.

Preparing wood before putting it in place

• Brush it under clean water, without soap or detergent.
• Soak it in a bucket or bathtub, changing the water every two or three days, until it remains more or less colorless. Allow anywhere from several days to a few weeks, depending on its size.
• If the piece fits in a saucepan, pouring boiling water over it significantly speeds up the release of tannins and helps the wood sink.

If the wood is already in place with the fish, there is no need to dismantle everything: activated carbon will do the job.

The milky haze: an aquarium seeking its balance

When an aquarium is restarted, especially after it has been emptied and cleaned, the colonies of beneficial bacteria in the filter are weak or absent. The available organic matter (food, waste, wood debris, new décor) then feeds free-floating bacteria that multiply in the water itself. The result is this uniform white haze, which can appear overnight.

The natural instinct is to change the water. That is precisely what perpetuates the problem: each large water change restarts the cycle, and if you rinse the filter with tap water at the same time, you destroy the colonies that are taking hold. In this specific case, the best strategy is almost to do nothing:

1. Stop large water changes as long as the fish are doing well. A small weekly water change is sufficient.
2. Do not clean the filter, and if necessary, rinse the media in aquarium water, never under the tap.
3. Feed very little, once a day, only what is eaten within one to two minutes.
4. Seed the filter with live bacteria to shorten the startup phase.
5. Monitor nitrites with a test: these are what endanger fish in a young tank, not the haze itself.

And what if it was neither the wood nor the bacteria?

Two rarer possibilities are worth checking. First, dust: insufficiently rinsed new sand or gravel, or dusty wood, leaves fine particles that the pump constantly resuspends. A layer of fine filter floss, changed frequently for a few days, will capture them. Then there may be a white, cottony deposit on the wood itself: this is a biofilm of fungi and bacteria that commonly appears on new wood during the first few weeks. It is unsightly but generally harmless, and snails or shrimp are happy to take care of it. You can also remove it with a toothbrush during maintenance.

By contrast, wood collected in a forest or along a riverbank, untreated, can introduce undesirable residues or rot in the water. With a branch purchased from a specialist store, this risk is very low.

The right order for crystal-clear water

Here is the sequence we recommend at the store when a customer comes in with this problem:

• Week 1: perform the glass test, stop large water changes, add activated carbon to the filter if the water is yellow, and add bacteria if the tank has just been restarted.
• Week 2: test nitrites, reduce feeding, and if necessary use a clarifier to clump fine particles together so the filter can retain them.
• Next: replace the carbon according to the manufacturer's instructions, because once saturated it no longer removes anything, then resume normal maintenance.

In most aquariums, the water becomes crystal clear again within two to three weeks. The wood itself continues to tint the water very slightly for a while; many aquarists eventually come to appreciate this amber hue, which recalls natural habitats.

Also read

For more information about other causes: Why does the water in my aquarium become cloudy?.

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Frequently asked questions

— Are tannins from wood dangerous for fish?

No, for the vast majority of freshwater fish. They may lower the pH slightly in very soft water; if you keep demanding species, simply monitor the pH.

— How long does new wood color the water?

It depends on the type and size: from a few weeks to several months for large pieces, gradually decreasing over time. Pre-soaking significantly shortens this period.

— Should the wood be removed if the water remains cloudy?

Rarely. If the water is milky, the wood is not the main cause: it is the tank's bacterial start-up. If it is yellow, activated carbon is generally sufficient.

— Why does the water become cloudy again after every water change?

Because large water changes, especially when combined with filter cleaning, restart the bacterial imbalance. Space them out and let the filter become colonized.

In summary

• Yellow and clear water = tannins from the wood; milky water = bacterial bloom during the start-up phase.
• Repeated water changes maintain the haze instead of removing it.
• Activated carbon for the color, bacteria and patience for the white haze.
• Soaking the wood beforehand prevents most of the coloration.
• Monitor nitrites while the tank is still young.

Last updated: September 29, 2026.