Biofilm on Drift Wood in Fish Tank

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Driftwood is a common tank decoration used by most aquarists, no matter the setup they have in place.

This decoration aids in the production of beneficial bacteria, lower water pH, and even serves as a food source for some grazing fish species like plecos.

Driftwood also looks nice, creating a more natural and vibrant aquatic environment which is great for aquascape hobbyists.

The problem is that driftwood also has some downsides, one of which is the biofilm that grows on it.

So, let’s discuss that.

What Causes Biofilm on Driftwood?

Your piece of driftwood will grow a biofilm whether you like it or not. This is a fungal or mold growth in most cases, often combined with colonies of bacteria that feed on the driftwood.

The biofilm often looks like a transparent mucus covering the piece, similar to Vaseline.

If left unchecked, the biofilm will grow and migrate through the tank, covering other surfaces and altering the water’s chemistry in the process. The main trigger is the driftwood’s sugar content.

Driftwood releases carbohydrates and other nutrients into the water, but most of these remain on the wood’s surface.

Needless to say, this will attract a variety of bacteria, mold, and fungi, as well as fish and other aquatic creatures.

The biofilm can become visible quite fast, usually within the first weeks of adding the driftwood to your tank.

Is Biofilm Safe for Fish?

Usually, yes, the biofilm is safe for fish. The only major problem to consider relates to the biofilm’s biological activity.

The biofilm itself is alive since it consists of billions of bacteria and other microorganisms. Like most living creatures, these microorganisms consume oxygen and produce CO2.

This isn’t necessarily a problem in heavily planted aquariums, where the plants will consume the excess CO2 and boost oxygen levels. But it can become one in more standard aquariums where you don’t have as many plants to correct the problem. As a result, you’ll have a growing biofilm that consumes the dissolved oxygen in the water and boosts CO2 levels, soon causing fish to experience breathing problems.

You can tell that your fish struggle with breathing if they go to the water’s surface more often. They also flash their gills more rapidly and open and close their mouth more aggressively, trying to take in more oxygen.

Best-case scenario, your fish will become stressed and soon experience health problems due to a stress-related weaker immune system.

Worst-case scenario, they will suffocate and die, especially since your live plants also take in oxygen and produce CO2 during nighttime, further contributing to the problem.

So, the driftwood biofilm may not be dangerous at first, but it can become dangerous under the right circumstances.

Do Fish Eat Biofilm from Driftwood?

Yes, but not all of them. Otocinclus catfish, bristlenose pleco, and a variety of snails will gladly consume driftwood biofilm, among other things.

Go for professional algae grazers since most eat pretty much anything they can find, including the biofilm in question.

Naturally, this isn’t necessarily a universal solution. The biofilm may be so large and aggressive that your cleaner-fish won’t be able to handle it.

And you can’t have a cleaner-only tank. In this case, you need some alternate, more effective methods of dealing with the nasty biofilm.

How to Remove Biofilm from Driftwood?

There are 3 primary methods of cleaning your driftwood and eliminating the biofilm in the process:

  1. Mechanical cleaning – This is only a pretentious term for ‘scrubbing the driftwood by hand.’ And it’s as easy as it sounds. You simply remove the driftwood from the tank and scrape the biofilm deposits by hand. You can use whichever tool you prefer, provided it gets the job done. Take your time and be thorough about it to clean off any crevice that may hide any biofilm chunks. The more thorough the cleaning and rinsing process is, the slower the biofilm will return. Because it will return eventually.
  2. Chemical cleaning – You have several chemicals to use, depending on your availability and preferences. We include here bleach, hydrogen peroxide, potassium permanganate, and even vinegar. The important thing to remember is the concentration. For bleach, for instance, the optimal solution contains ½ a cup of bleach for every 5 gallons of water. You’re safe with ½ a cup for 1 gallon of water for vinegar. Important to note – rinse the piece of driftwood with tank water thoroughly and give it time to dry out completely. The wood is porous, and it may retain some of the chemicals if you don’t rinse it properly.
  3. Boiling the driftwood – This is as easy as it sounds. First, remove any large chunks of biofilm by hand, then boil the driftwood for 5 minutes. This is enough to sterilize the piece completely. Allow the driftwood to dry out and place it back into the aquarium.

Be very careful about the chemical cleaning part. The driftwood will soak in some of the chemicals you’re using. So, don’t go overboard with those and stick to a safer concentration.

Even if the biofilm appears thick and stubborn. You better use more scrubbing than adding more bleach or vinegar that will soak into the wood and dissolve into the tank water, poisoning the fish.

How to Prevent Biofilm Forming on Driftwood?

Fortunately, there are several prevention mechanisms you can use to prevent the formation of biofilm.

Unfortunately, they are not all equally as effective or as safe for your fish tank. Whichever you use depends on your setup, what fish you have, and your tank’s overall layout.

Here are the options to consider:

  • Minimize food residues – The tank’s biofilm consumes a variety of nutrients resulting from decaying organic matter. Overfeeding your fish results in excess food residues, which end up feeding the tank’s biofilm. You have 2 solutions in this sense: don’t overfeed the fish and clean food leftovers more frequently. These strategies will minimize the organic waste that contributes to the biofilm’s expansion. When it comes to the overfeeding aspect, your fish should only get sufficient food for them to consume within 1-2 minutes.
  • Mind liquid fertilizersFloating plants require liquid fertilization to thrive. The problem is that liquid fertilizers are notorious for promoting a thick and healthy biofilm and supporting algae overgrowth. It’s hard to get one without the other, but not impossible. Only provide your plants with the exact amounts of fertilization they need and nothing more. Going overboard will cost you.
  • Always have cleaning fish available – All aquariums should have at least 2 different species of cleaning crew available. Otocinclus catfish, plecos, snails, and some species of shrimp all consume biofilm and algae. They also eat food leftovers, keeping the habitat cleaner and healthier. Their presence will keep the biofilm under control, at least to some degree.
  • Regular tank maintenanceWater changes, substrate vacuuming, and general cleaning are all important in keeping the aquatic setup clean and healthy. These strategies also prevent the formation of surface and submerged biofilm and algae and maintain healthy water chemistry. Set up a steady cleaning routine, and you will greatly minimize the biofilm’s impact.

In reality, all these rank more as control than prevention methods. That’s because your tank will grow biofilm constantly; you can’t really prevent that.

You can, however, rely on control methods designed to outpace the biofilm’s growth rate and keep it in check.


Setting up an aquarium is you signing up that you want biofilm in your life. It’s okay, it’s part of keeping a fish tank.

Fortunately, there are ways to mitigate the biofilm’s impact and hinder its development over time.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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