Are Plastic Tanks Bad For Fish? (Plastic Vs. Glass Fish Tanks)

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When transferring your fish to plastic tanks, questions often arise about their safety.

As a general rule, plastic tanks are not bad for fish tanks because most plastics are inert and don’t get dissolved even if you put water in them.

Read on to find out what type of plastic is safe for fish tanks and the comparison between glass and plastic tanks.

What Types Of Plastics Are Safe For Keeping Fish?

Generally, any plastic container made of food-grade material should also be safe for keeping the fish. Also, tanks made of special plastic material like acrylic are safe for fish because they are specifically made for fishkeeping.

my-hand-holding-a-plastic-container
Holding-a-plastic-container

A food-grade plastic is specifically designed to work well and safely when used for keeping food. There are strict quality checks the plastic has to go through to be considered food-safe. 

Food-grade plastics are supposed to not leech any chemicals with the food they come in contact with because any chance of leaching chemicals would impact the taste of the food and also have a bad impact on the health of the person consuming the food.

If you use a food-grade plastic material, you can be assured that they don’t typically leach. And this criterion is enough to qualify as our suitable plastic material for keeping fish.

So whether you are keeping a betta fish or any other in a plastic tank, it’s perfectly fine if you choose a food-grade plastic material.

Now the big question:

How can you identify whether plastic is food-grade or not?

The SPI (Society Of Plastic Industry) has launched different codes for plastic. And these internationally accepted plastic ids will help us to identify whether the plastic is food grade.

  • Take any plastic container and turn it upside down.
  • Then, look at the bottom of the plastic container for a triangular symbol and a number inside it.
  • The number inside that symbol will tell you whether plastic is safe for usage or not.
  • Usually, plastic containers suitable for storing food (and hence also good for aquarium and fishkeeping usage) have the numbers 2, 4, or 5.
  • Any plastic container with a number 3 or 7 is not safe because the plastic can leach chemicals.
Safe ✔️Unsafe ❌
Plastic containers with id: 2, 4, or 5Plastic containers with id: 3 or 7
the-back-part-of-a-plastic-container
Showing-the-plastic-code-present-at-the-bottom-of-the-plastic-container
Plastic CodeMaterialUsed In
2High-Density Polyethylene (HDPE)Milk Containers, Food Storage Buckets, or Containers
4Low-Density Polyethylene (LDPE)Frozen food bags, Dry cleaning bags
5Polypropylene (PP)Yogurt containers, Medicine bottles

What Are Acrylic Fish Tanks?

Acrylic is a form of plastic material with better strength and clarity. Like glass fish tanks, acrylic fish tanks are often sold for fishkeeping.

Since acrylic fish tanks are designed for aquarium hobby usage, they are also safe for the fish. In addition, they have some advantages that even glass fish tanks don’t offer.

For instance, acrylic fish tanks are quite lightweight than glass tanks. So if you want to set up your tank upstairs or in any other position where carrying the tank could be an issue, the acrylic tanks are very helpful.

Then, plastic fish tanks don’t tend to break as easily as glass tanks. (Yes, fish tanks can crack if you don’t set and use them properly.)

Another noteworthy thing about acrylic fish tanks is their insulation property. Acrylic tanks are made of plastic.

And plastic materials have much lower thermal conductivity than glass. So, in other words, if you take a glass and plastic cup of equal thickness, the insulation property of the plastic glass will be much more than that of a glass cup.

The glass will let the temperature conduct more easily; as a result, the temperature fluctuation will be relatively higher than in a plastic tank. That said, you can handle temperature fluctuation with good-quality aquarium heaters.

Bit plastic tanks also have some downsides. And the number one issue with them is the tendency to get scratched easily. So if you scrape your plastic tank carelessly with any hard material, be prepared to see noticeable scratches.

Another issue with plastic tanks is that their clarity won’t remain constant. As the plastic tank (especially acrylic aquarium) gets exposed to light over time with usage, they tend to develop a yellowish tint.

Over time the acrylic aquariums can become cloudy, but the same is not true for glass aquariums.

Finally, another issue with acrylic aquariums is the cost. Glass is a very popular option for fish tanks and is usually available for at least 2x cheaper than acrylic aquariums of the same structure.

Plastic Fish Tank Vs. Glass Fish Tank

Plastic (Acrylic) TanksGlass Tanks
Lightweight 🟢Relatively Heavier 🔴
Less Chance Of Breaking 🟢Easy To Break 🔴
Expensive (if a complete acrylic aquarium is considered) 🔴Generally Cheaper 🟢
Easily Scratches 🔴Relatively More Scratch-Resistant 🟢
More Design Options Available 🟢Less Designs Options Available 🔴
More Heat Insulation 🔴Relatively Less Heat Insulation 🔴
Clarity Is Affected With Time 🔴Remain Clear 🟢

Who Is The Winner?

Well, that depends on your individual needs. But overall, glass aquariums are usually the standard in the hobby. Go to any fish store and look at the shelves. Most aquariums you will see are made of glass.

So that indicates how popular glass is as a fish tank.

In short, choose glass aquariums if:

  • You want something relatively cheap and standard.
  • You want a tank that tends to scratch less and offers constant clarity.

However, choose a plastic (acrylic) aquarium if:

  • The tank’s weight is a big issue for you and you want something lightweight.
  • You are looking for a tank that has a unique shape and offers more insulation.
our-home-glass-fish-tank
Our-glass-fish-tank-at-home-meet-with-the-lovely-red-parrot-fish

If we were to buy another aquarium, our first preference would be glass – because we personally like the feel of the glass fish tanks, their clarity, and the less scratching tendency.

But it’s fine to go with either glass or plastic depending on your priorities. So I hope you have a clear picture of what should work best for you.

What’s next? Have you ever wondered whether it is a good idea to keep the fish tank covered? To learn more check out this guide: Should You Keep The Fish Tanks Open or Closed? 

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By Praveen Ghoshal

Hi! I'm Praveen Ghoshal, the founder of eFishkeeping.com. Inspired by my Dad, I got interested in fishkeeping when I was a kid. Since then, I have been involved with this hobby. Currently, I have 3 fish tanks at our home, where I enjoy this hobby with my Mom, Dad, and Younger Sister. Read more about me here.