Biofilm is a common problem, especially in planted tanks. Even the best aquascapers do occasionally see it in their aquariums. While there is no definitive answer on the exact causes and composition of biofilm (there can be different types), there are a few common opinions based on anecdotal testing and research:
What is Biofilm?
Generally speaking, biofilm is the carbohydrates and lipids from organic waste produced in a planted tank. Specifically, the ‘film’ is produced by bacteria feeding on the excess organic waste present in the water — and that organic waste can come from livestock and plant life in the tank.
Biofilm is the carbs/lipids excreted by stressed plants
A popular viewpoint (supported by various anecdotes) is that biofilm only forms when plants are unable to take in enough nutrients from the water column, whether due to higher alkalinity or a simple lack of proper dosing.
Biofilm is a temporary symptom of new tanks
Another viewpoint is that biofilm is simply a ‘phase’ that some new tanks pass through as the bacteria matures and reaches an equilibrium. According to this theory, once the tank matures, the biofilm should dissipate.
Solving The Problem
So, how do you fix it?
Well, the aquarium community has a few different opinions on the exact conditions that cause biofilm, but it’s generally agreed that you can do three things to solve it once and for all:
Use a skimmer
A skimmer is often used in saltwater tanks, but in the last few years the freshwater community has seen benefits from the use of a small skimmer. Many common filters allow for a combination skimmer/pipe intake, and they’re easily the most effective method of removing (and preventing) biofilm buildup.
Some can look unsightly, so we’d suggest using a glass or acrylic version if you’re able. Here’s the model we use on most of our tanks:
Simple, effective, and doesn’t clutter the visuals of your tank like other materials.
These have lasted us for years, and keep the surface clear of biofilm buildup. Anecdotally, we’ve seen slightly better growth in flora from the increased light that’s no longer blocked by surface film.View on Amazon
Increase your O2 levels in the water
Biofilm has been known to form at the water surface because it’s seeking higher O2 concentrations than what it can find dissolved in the water. Surface agitation with a powerhead, filter output pipes, or anything else that agitates the surface will increase your O2 levels. If you’d like, you can also use a gadget like the TwinStar Nano to get more O2 into your water.
Increase your water flow
Weak flow in the aquarium has also been shown to be cause of biofilm. Ideally, your filter output should be at least 10 times the size of your tank to provide plenty of turnover and flow. It’s also a good idea to check for ‘dead’ spots where water isn’t moving. If you find any, a powerhead is a great solution for this.
Check your dosing
Finally, check that you’re providing the proper nutrients for your plants. Plants naturally produce carbohydrates and lipids as a part of photosynthesis. If they’re having trouble ingesting nutrients from the water, or there simply aren’t enough nutrients, this production of carbs and lipids is increased, which can lead to the biofilm on the water surface.
Biofilm can be mysterious when it appears, but if you increase O2 levels, fix any weak flow, and check your dosing, you should see it disappear within a day or so.
What’s your solution?
We’ve all probably encountered biofilm at one point or another in our aquascaping. What did you do to solve it? What do you find causes biofilm to occur? Let us know in the comments!