Do Platy Fish Need A Filter?

Clean water is a basic requirement to keeping Platies happy and healthy. Generally, Platies don’t make as much waste as, say, Goldfish or Mollies do.  But if your water’s chemistry is fluctuating, then there’s something wrong.

Yes, Platies will benefit greatly from a filtration system that removes toxins from the water.

But when it comes to using filters in Platy tanks, there’s so much information that it confuses many. Here we break down the basics so you can make an educated decision yourself.

Why Do Platy Need A Tank Filter?

Here’s a simple explanation:

Being a live animal, Platy needs to eat.  And because it eats, it’s going to create waste.  On the top of that leftover food and dried leaves from plants will rot and become waste, too.  All those toxins are harmful to your fish, therefore, your Platy also needs a filter to remain healthy and happy.

The key question will be why my Platy’s tank getting dirty so quickly. Let’s see.

Why Does My Fish Tank Get Dirty So Fast?

You might be considering a filter to improve your water quality.  But let’s get to the root of the problem.

Overfeeding and having too small of an aquarium are two things that contribute greatly to tank water pollution. 

Overfeeding results in too much poop and uneaten food.  It is a bad habit of too many fish keepers.  Overfeeding happens because:

  • We get satisfaction when we feed our fish, so we feed often
  • We don’t know how much to feed our fish
  • There’s more than one person who feeds our fish
  • The label on the fish food says we should feed our fish three times a day.

Platies need only be fed once or twice a day in small amounts.  Most seasoned hobbyists even skip a day or two every week to clear out their Platies’ digestive systems.  Overfeeding Platies is bad because it will cause constipation, too much poop, uneaten food at the bottom of the tank, and ammonia spikes.

If you’re overfeeding, then the tank size matters.  Small tank sizes mean less water.  And less water means a faster spread of toxins.  If you don’t want your small tank to get polluted quickly then you have to feed your fish less food.  That doesn’t mean you’ll starve them, it simply means you won’t overfeed them.  You also have to make more frequent partial water changes.

Additionally, frozen food may make your tank water cloudy (or even smelly).  This is caused by the liquids they’re frozen in.  To remedy this, thaw, wash and drain frozen food first before serving it to your Platy fish.

If you don’t correct these factors listed above, you’ll have a hard time keeping your water clear and balanced and you will need good filtration.

What Is A Tank Filter?

Having a tank filter will indeed help stabilize your water.

Do platy fish need filter?
Do Platy Fish Need A Filter?

An aquarium filter is a means of removing waste inside your fish tank.  These wastes include ammonia, nitrates, and debris that may be making your tank water dirty. It also increases the aeration of the water.

How Does A Fish Tank Filter Work?

Mechanical, biological, and chemical filtrations are the ways to clean your tank water.

Undissolved solids or bigger particles such as bits of food and poop are filtered through mechanical filtration.  This is done through sponges, filter floss, filter socks, and other similar materials with tiny holes that can sift through particles while letting the water through.

Biological filtration is the use of helpful bacteria to convert harmful bacteria (or bioload) into harmless organisms.  These helpful bacteria grow on different surfaces in your tank: the substrate, the plants, the rocks and decorations, and even the sponge in your mechanical filtration. 

The more surface area you have in the tank, the more helpful bacteria exist to continuously filter your water.

Biological filtration is simply a completed nitrogen cycle.  For more on the nitrogen cycle, search our posts “Do GloFish Really Play Dead?” and “9 Reasons Why Guppies Die”.

Similarly, chemical filtration breaks down harmful bacteria into harmless organisms but through the use of chemicals such as activated charcoal and filter resin.  Unfortunately, chemicals are temporary solutions and you’ll have to keep adding more from time to time for it to be effective.

Chemical filtration is not necessary for a Platy tank.

What Type Of Filter Is Best For A Fish Tank?

Platy fish are not very demanding fish except for Swordtail Platies which are a little more sensitive to ammonia and nitrates.

You already have biological filtration with properly cycled water.  What you need for Platies is just the standard mechanical filter.  There are many options in the market and the most common are the sponge filter, the hang-on-back filter, and the canister filter.

Sponge Filters

are simple-constructed devices composed of a sponge, airline tubing, and an air pump.  These filters are effective and do not create a lot of current in the water so it’s safe for fry and juveniles.  It takes up space inside the tank, though.

Hygger Aquarium Double Sponge Filter gives you great value for your money.  This air-driven filter saves space (especially if you have a narrow tank) because it can be stuck on the side of the glass unlike other models where it sits somewhere on the bottom of the tank.  And because of the double sponge, you don’t lose a lot of beneficial bacteria as you can choose to replace only one sponge at a time. 

It might not be the best-looking sponge filter in the market but it does its job really well.  Besides, you can always hide it behind plants and décor in your tank.

Hang-on-back Filters

These are the standard filters in aquarium kits today.  They usually fit through the lid cover and are hung on the side or back of the tank.  The advantage it has over the sponge type is that you can add more sponges in this one like a coarse pad or a filter floss pad to maximize filtration.

SeaChem Tidal 35 packs a punch when it comes to the most desired features in a hang-on-back filter.  It has an internal pump that’s powerful, silent, and effective, a large tray that can hold your preferred filter media, adjustable flow (perfect for juveniles Platies), and extra spaces for things like your heater. 

And for most people who don’t really like the process of cleaning tubes, the Tidal 35 has a self-cleaning impeller!

We love the highly customizable features.  And it’s not even the most expensive in the market. 

Canister Filters

These are the more expensive of the three but they do have the advantage of being able to provide biological, mechanical, and even chemical filtration.  That being said it’s not the easiest to set up and will require costlier maintenance.

Canister filters cost a pretty penny but it’s all worth it if you get one with a durable, cost-effective motor that won’t drive your electricity bill through the roof. 

Consider the Fluval 307, a quiet and sleek filter which makes your tank water crystal clear.  It has all the features you’d want in a filter plus more.

The Fluval 307 is great for community tanks with up to 70 gallons capacity.  It’s fairly easy to install and replacement parts are widely available.

Your Platies will surely benefit from the use of any of these filters.

As for fancier types of filters such as bed filters and power filters, Platies don’t need them unless they have tank mates that are producing more waste. 

How Do You Clean A Mechanical Filter?

When visible dirt and particles start floating in your tank water, and your filter seems to be clogged or giving off fewer bubbles than usual, it’s time to clean the filter.

Platy fish needs tank filter
How Do You Clean A Mechanical Filter?
  • For sponge filters: detach the sponge from your filter and wring it out under old tank water. 
  • For hang-on-back filters: remove the intake stem and tube, plus the impeller, and clean with a circular brush.  Then wash your bio rocks (if any) and wring out the sponge under old tank water. 
  • For canister filters: unplug from your power source and detach the pipes.   Disassemble the parts including the motor, filter media, media tray, impeller, and shaft.  Wash each part thoroughly.  Remove the filter media and the water left in the canister.  Wash the canister thoroughly.

Activated carbon should be replaced every 3 to 4 weeks.

Replacing sponges can range from 6 months to yearly.  Replacing the whole filter can take years if you do regular maintenance and cleaning.

Aside from mechanical filters, there is a type of anti-particle filter that doesn’t need electricity for power: live plants.

How Do I Know What Size Filter I Need?

The more waste that’s produced, the dirtier your water becomes.

It’s not the size of the tank that directly becomes the basis for how much or how powerful filtration you will need but the amount of waste you need to filter and the condition of biological filtration in your tank.

The size of a filter is measured by gallons per hour (GPH).  For example, a 20-gallon planted tank with about 5 to 7 Platies will only need a filter with 64 to 100 GPH water capacity.  A 55-gallon with the same amount of fish and lots of plants would need a 175 GPH filter.

However, if your 20-gallon looks very erratic and you can’t seem to fix it, you can already start with a 100 to 120 GPH filter.  But be sure to look into overfeeding and cycling problems to give a permanent solution to the fluctuating water chemistry.

Do Plants Filter Aquarium Water?

Live plants have a lot of benefits to Platies.  Among them are shelter, safety, oxygenation, and yes, natural biological filtration.

Plants use up ammonia, nitrates, and carbon dioxide in the tank to grow.  And they breathe out oxygen, providing a good source of air for your Platies.

As we mentioned, plants are also where good bacteria cling to as it provides more surface area to grow.

And they look good in your tank, too!

Therefore, plants are always good for Platies and all other types of fish.

Can You Have An Aquarium Without A Filter?

Since live plants provide all the benefits that a mechanical filtration does, they can replace the devices completely as long as there is a lot of it (plants).  This means a large enough, heavily planted tank with few fish and controlled feeding.

It takes some skill and lots of experience to achieve this ecological balance.  Most who do this are experts in aquascapes, seasoned fish keepers, and overseas fish breeder farms.

One important thing to do is to regularly check your water for the correct chemistry levels (ammonia, nitrates, pH) as it will ensure that your filtration is on point. 


Filtration is key to keeping Platies healthy and biological filtration is always the bottom line of every tank with the nitrogen cycle. 

Mechanical filtration may not be necessary if your biological filtration system is more than enough to handle waste production.  In the case of Platies, there’s not a lot of waste to deal with.

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