How to Get Rid of Surface Scum Without a Skimmer?

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Long-term aquarium maintenance is necessary to keep the system stable and healthy for your fish and plants. Unfortunately, conditions may sometimes be less than ideal. So, surface scum will form on the water’s surface.

This is essentially dirt, disposable organic matter that warns of some environmental issues that need addressing. So, let’s check the belly of the problem!

What Causes Surface Scum in Fish Tank?

First, what exactly is surface scum? We’re talking about a thick layer of foamy matter, usually milky-green in coloring, somewhat similar to an algae blanket.

Surface scum is a mix of dead organic matter, plant protein, mucus, and many bacterial cultures.

Surface scum also appears oily at times, depending on what’s causing it. The layer can grow quite thick over time if you ignore the problem long enough.

So, what’s causing the problem? There are several potential causes to discuss:

  • New plants – This may be a surprising point, but it’s true nonetheless. Plants take time to accumulate to a new environment, during which they will eliminate proteins into the surrounding water. These will accumulate at the water’s surface, where, in conjunction with other organic matter, will form the surface scum we’re discussing. This natural process happens even in the healthiest and most well-maintained environments.
  • Immature tanks – New tanks take time to build a self-sustainable biological foundation. Until that happens, your aquatic system will lack the bacterial power necessary to filter and manage the waste. This will accumulate on the surface, and we all know where that leads. The situation should correct itself once the tank has matured. Until then, you better remove the accumulating scum yourself to prevent it from suffocating the environment.
  • Improper environmental oxygenation – Aquatic systems contain billions of microorganisms, mainly microbes that also breathe oxygen. If there isn’t enough of it in the water, these organisms will migrate to the water’s surface, where oxygen levels are higher. They will soon crowd the water’s surface, which will cause them to aggravate the problem. That’s because surface scum is known to impact the gaseous exchanges in the tank. So, the oxygen levels will drop even further, aggravating the situation.
  • Excess iron – Iron is often used as fertilizing component in plant fertilizers. Plants need this element to survive, but too much can backfire fast. That’s because bacteria also consume iron, which accumulates at the water surface.
  • Excess CO2 – CO2 is necessary for planted aquariums. Live plants consume CO2 as part of their photosynthesis process since they need it for their gas exchanges. They consume CO2 and produce oxygen during the day and consume oxygen and produce CO2 during nighttime. The problem is that, in heavily planted aquariums, the natural CO2 that’s being produced may not suffice. If that’s the case, you need to supplement the environment with CO2 injections. The problem is that the more CO2 the plants have, the faster they will grow, eliminating more protein and dead matter in the process. So, surface scum is always more likely to form in aquariums with fast-growing plants.

As you can see, the surface film has many causes. However, despite the cause, one thing is for certain – surface scum can have a deadly impact on your aquatic life. The situation needs a solution fast.

Fortunately, I have not one but 5 solutions for you.

6 Ways to Combat Surface Scum in Fish Tank

Now that you’ve identified the problem let’s work towards figuring out the ideal solution.

To do that, you must first identify what’s causing the issue. In this sense, you have the following 6 potential courses of action:

1. Cleaning the Filter Regularly

Any decent, healthy aquatic setup requires a reliable filtration system. The filter is designed to remove fish waste, food particles, and dead organic matter and reoxygenate the environment.

A clogged or faulty filter will imbalance the system, causing accumulated dirt and scum to migrate to the water’s surface.

Ideally, you should have a well-established cleaning routine in place designed to keep your filtration system in peak condition.

At the very least, you should investigate your filter once every 2-3 weeks to see if it needs cleaning. If it does, consider the following:

  • Don’t use any chemicals in the process as these could kill the denitrifying bacteria colonizing the filter
  • Don’t use tap water since the added chlorine will have the same effect
  • Don’t scrub the filter too thoroughly for the same reasons

You should preferably use aquarium water during the cleaning process to preserve your cultures of live bacteria.

And remember that while the filtration system requires regular cleaning, you shouldn’t do it too often.

Excessive cleaning will depopulate the filter of the beneficial bacteria that control nitrate levels.

2. Avoid Overfeeding Your Fish

Overfeeding your fish is never a good idea. I understand how some people have that instinct, but you shouldn’t go on instinct on this one.

Overfeeding causes fish to experience digestive problems, resulting in several immediate problems:

  • The fish will poop more often, adding more waste to the environment
  • The fish will become constipated or compacted, which can turn deadly in some cases
  • Your fish won’t be able to consume all the food, causing the leftovers to rot, leading to ammonia and nitrate spikes

The situation worsens when housing species like goldfish, which are already notorious for their industrial pooping capabilities. Only feed your fish moderate meals that they can consume within the first 2 minutes. Anything above that is excess.

With regards to frequency, most aquarium fish only have 1 to 2 meals per day at most. Some only eat once every 2-3 days.

So, always learn about your fish’s eating habits based on their species, size, and any other relevant parameters.

3. Increase Water Filtration

If you have insufficient filtration power, boost it up a bit. The more powerful filter will achieve 2 things for you:

  • Eliminate more residues and waste and
  • Improve surface water agitation

Surface scum is typically a mix between dead organic matter, plant fat, and bacteria. Surface agitation will prevent the mass from forming, breaking it down and allowing the filter to suck it up.

Fortunately, this will happen gradually, as the muck isn’t fully matured. So, the filter won’t clog when that happens.

Effective filtration systems are also better at cleaning the environment and removing floating particles and matter that accumulate in the water over time. This way, they will prevent the formation of surface scum in the long run.

4. Use an Air Stone

Air stones improve water oxygenation, preventing bacteria from migrating to the water’s surface.

They also benefit fish and plants by keeping the oxygen levels up. Just make sure that your fish aren’t too bothered by the air stones’ activity.

Not all of them like the bubble currents forming in their habitat.

5. Water Surface Agitation

You can typically achieve this via your filtration system. Just place the filter’s output closer to the water’s surface, and the problem is solved.

Well, not solved, but at least the surface scum will have more difficult times forming. The filter’s activity will push it to the side, making it easier to remove manually.

6. Regular Water Changes

We couldn’t have skipped this one. Water changes are necessary to preserve water quality, dilute nitrates, reoxygenate the environment, and, of course, remove surface scum.

The frequency of your water changes depends on the tank’s size and the fish species you’re housing. Some fish, like cichlids, goldfish, or Oscars, demand more frequent water changes because they poop more.

Heavily planted tanks also demand frequent water changes, as are tanks where fish are regularly overfed.

You should probably perform one partial water change per week or, at a minimum, every 2 weeks.

As a general guideline, the smaller and the more stocked the aquarium is, the higher the frequency of the water changes necessary.

Naturally, there are other removal methods as well, like:

  • Using a skimmer – The skimmer sucks all the surface biofilm to keep the water clean and more well-oxygenated. Many aquarists prefer not to use the skimmer due to taking up valuable space in the tank. They already have a filter installed which takes sufficient space as it is. Otherwise, this is a good way of keeping your tank water safe from surface scum.
  • Using kitchen paper – You simply place the paper on the water’s surface and wait for it to soak up completely. This shouldn’t last more than several seconds. The paper will suck in both water and surface scum, cleaning the water’s surface quite effectively. The main problem is that it doesn’t remove larger particles, only the finer biofilm. Still, it’s better than nothing.
  • Surface-eating animals – Some aquatic animals consume surface biofilm as part of their daily diet. These can reduce the impact of surface scum, but don’t expect them to work wonders. They’re only moderately effective at their job.

Conclusion

One thing to know about surface scum is that it tends to form more in heavily planted aquariums. That’s because plants eliminate proteins, fat, and organic matter as they grow.

All of this accumulates on the water’s surface, where it forms the infamous surface scum with dire long-term consequences. Surface scum will essentially suffocate the environment because it prevents gaseous exchanges at the water’s surface.

In other words, oxygen can’t get in, CO2 can’t get out, and fish will die.

Not to mention, a thick-enough layer of surface scum will prevent light from penetrating deeper water levels, causing the plants to die.

Fortunately, now you know how to handle the problem.

avatar 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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