Diatomaceous Earth Filter for Aquarium – All You Need to Know

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Every aquarium requires a stable and effective filtration system to maintain the water clean and healthy. The filter oxygenates the water and removes floating particles, viruses, and chemicals for a cleaner and healthier habitat.

Naturally, not all filters are equal in terms of efficiency or working mechanism.

Some only offer mechanical filtration, others focus on biological sterilization, while others, like activated carbon, clean the water of various chemicals.

Many types of aquarium filtration systems are available, depending on size, filtration power, functioning mechanism, etc.

Today we will discuss a more interesting filtration system, the diatom one. This one was once pretty popular in the aquarium business but has fallen out of grace as of recently. But why is that, and can and should you use one? Let’s see!

What is a Diatomaceous Earth Filter?

A diatomaceous filter is a filtration system that uses diatom earth to filter the water. Diatom earth gets its name from the fossils it comprises of.

Diatoms are single-celled algae that use silicates from the surrounding environment to harden the exterior of the cell. They essentially form a silica wall around them to turn themselves more resilient to their environment.

This cell wall turns the algae into hardened micro-fossils after death. In other words, they become diatoms, simply a sandy mass of billions of dead fossilized shells.

These shells have porous surfaces, with each pore containing other smaller pores, often as small as 0.5 microns.

All these pores trap a lot of floating particles, allowing the diatom earth to function as an effective mechanical filtration system.

Some people also believe diatoms provide biological and chemical filtration, so we’ll get into that as well.

Is Diatomaceous Earth Safe for Fish and Plants?

Yes, diatom earth is considered safe for fish and plants. However, you will get a lot of conflicting information on this topic, unfortunately.

One of the main problems some people have noted has to do with Amano shrimp. Some people reported losing their shrimps when using a diatom filter.

The shrimps simply convulsed and died soon after being added to the tank. This could be blamed on X number of factors if it wasn’t for the diatom filter. That’s because, once the filter was removed, the shrimp simply stopped dying and thrived. Even though all other aquarium parameters stayed the same.

This makes sense because diatom earth is nothing more than a mass of fossilized and hardened algae shells.

This means that diatoms are abrasive, hard, and sometimes sharp, capable of causing internal problems to more sensitive animals upon ingesting. Shrimp may be more sensitive to diatom powder than fish.

There are no studies showing that diatoms are harmful to fish, though.

Benefits of Diatomaceous Earth Filter

Diatom filters come with their own pluses and cons, the latter of which explains why these filters aren’t as popular anymore.

But let’s start with the benefits:

  • Great mechanical power – Diatom filters are very small and fine and contain a lot of micropores. This allows the filter to stop and collect a lot of microparticles floating in the water, including floating algae residues. As a result, the water will get cleaner fast.
  • Potential biological filtration – Many people claim that diatom filters also cleanse the tank water of various parasites and viruses. However, there is no definitive evidence to corroborate these claims. So, take them with a…salty grain of salt.

Drawbacks of Diatomaceous Earth Filter

  • Rare – Diatom filters aren’t as popular as they used to be. So, you’ll have to perform some extra work to find the type of diatom filtration system you need.
  • No biological or chemical filtration – Despite the various anecdotal claims, there’s no evidence that diatom filters offer biological and chemical filtration. They’re good mechanical filters, but that’s about it. They may trap some larger pathogens, but they’re less effective overall. So, they don’t qualify as biological filters.
  • The need for more frequent cleaning – Diatom filters require more cleaning work due to the pores getting overwhelmed fast. Especially in dirtier and murkier environments that require higher filtration power. Many people have reported that diatom filters slow to a crawl after 2-3 days of functioning, while others didn’t even get this far. In their case, the diatom filter became hopelessly clogged within a few hours of functioning.
  • Danger to humans – As I’ve already stated, diatoms are sharp and abrasive particles that will irritate the lungs and cause respiratory problems. They will also irritate the skin upon contact, especially when there’s friction involved. Always use gloves, a respirator, or a mouth-and-nose cover to prevent these problems.

Overall, I would say that diatom filters are too much work and not enough turnaround.

Especially when considering that far better filtration systems are available on the market, providing superior power and improved filtration effects and demanding less maintenance.

How to Make Diatoms Filter for Your Tank?

Building your own diatom filter isn’t too difficult unless you make it out as such. Some recommendations include crafting a separate diatom container out of a PVC pipe and connecting that to your main filter.

The water will get traverse the diatom-filled PVC pipe before reaching the filter’s main media. So, you’ll sort of get 2 filtration systems in one.

This is too convoluted and requires more work and precision. So, I would skip this one completely and opt for a simpler version:

  • Prepare a 5-gallon container where you will add approximately 6 tbs of diatom earth; you can add more, depending on how large the main filtration system is
  • Use the main filter to clear the water in the container, which should take approximately 10-20 minutes, based on the filter’s power and how much diatom you’ve used
  • When the tank water clears up, you know that the diatom is now impregnated in your filter’s main media channel
  • Move the main filter into the fish tank and let it run for another 30 minutes
  • The added diatom matter should clean your tank of algae residues fast
  • Once the water is clear of algae, you remove the filter media and clean it thoroughly to remove the diatom

As you can see, this method uses diatom earth as part of a one-time cleaning method. It’s quite fitting, given that diatom filter media clog quite fast anyway.

The other option is to get a fully-functioning diatom filter yourself.

Where to Buy Diatomaceous Earth for Filter?

Amazon and Walmart are your best friends in this sense. Fortunately, the diatom earth itself is easier to find, compared to the actual diatom filter.

It’s also quite affordable.


Diatom filters aren’t exactly popular nowadays, but you can make them work. They’re quite effective in terms of chemical filtration and can make for a fine tool if you’re experiencing algae-muddied waters.

The filter will clean the tank water fast.

The downside is that diatom media clog fast, making them more short-lived than other, more modern filtration systems.

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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