Fish Tank Decorations: What Should You Never Put In Your Tank?

We independently research our recommended products. We may receive commissions on purchases made from our links.

Bringing fish into your home isn’t as complicated as bringing another type of pet into your life, right?They’re going into an enclosed tank, instead of running around your house, so the upkeep should be minimal.

While that’s true to an extent, there are still health and preparation elements that you’ll need to take into account in order to ensure that your fish live as healthy as possible.

is plastic safe for fish tanks

Ask yourself, “what can I put in a fish tank?” before you go on a buying binge, and keep some of the following essentials regarding tank decoration, size, and safety in mind. Your fish will thank you for the extra attention!

Preparing a Fish Tank

Before figuring out how to decorate a fish tank with household items, you’ll want to make a few key decisions about the rest of your aquarium.

The species of fish, your budget, the size of the tank, and any style choices you may have all need to work together.

If they don’t, you risk exposing your fish to health complications or infighting that could cost them their lives – and you that investment!


First things first: when debating toy placement in the fish tank, you’ll want to have your ideal tank occupants in mind.

Larger fish – like goldfish or bettas, for example – won’t find the same sorts of toys stimulating as smaller fish like guppies or gourami.

Providing hiding places, too, becomes more difficult if you don’t have your preferred occupants in mind.

Some fish don’t need hiding places, but those that do and those that are larger will obviously need sizable toys within which (or behind which) to hide.

Smaller fish can make use of standard, non-custom hiding places, but if exposed to some of the toys or tank structures that larger fish use, they may still feel unsafe.


Once you have a preferred breed of fish in mind, you’re only halfway to determining what kind of items you can include in your tank.

The type of tank, the decorations, and the placement of toys all depend on the breed of fish you intend to keep and how you want to interact with those fish.

If your intention is to breed the fish, then aquarium decorations will overall be unnecessary. However, if you have intentions of just viewing your fish, you’ll still need to consider the size of your tank, so the decorations can stimulate your fishes’ interests without blocking your vantage point.

Available Fish Tanks

A tank’s size may vary based on what that aquarium is made for; tanks can be exceptionally unique or reasonably standard.

Breeding Tanks

Breeding tanks, which you will not necessarily need to customize with decorations, are tanks that you’ll look to purchase if you focus solely on breeding your fish.

These tanks frequently have separate, specialized areas in which fish can lay their eggs. These areas can also be used to isolate the fry after they’ve grown larger (but are not ready to be introduced to the group), or to keep aggressive species from fighting in between breeding sessions.

The size of these tanks will enable you to keep better track of fish fry as they hatch and to control the breeding times of your aquarium.

Display Tanks

If you’re seeking a tank that’s a little higher quality than your standard variety, then you’ll want to consider a display (or show) tank.

These tanks come with lids that will prevent even the most athletic of fish from leaping out of their water. They also provide a higher number of filter slots that will make it easier to keep the tank clean, especially if you own a wide range of species.

If you’re hoping to customize a tank, then show tanks also stand out from the rest of your options, as they come in more unique shapes, such as a crescent or curved.

seashells in aquarium

Finally, you’ll be able to transfer filters and accessories from other tanks into your show tank without an issue.

Horizontal Tanks

Horizontal tanks are, predictably, long. They place the bulk of their surface area in their horizontal length, meaning that they’re likely to be laid down across a desk or placed into an aquarium wall.

There aren’t any accessory benefits when it comes to long tanks, but larger breeds of fish sometimes prefer having the additional room to swim, as these tanks imitate the length of a river.

Vertical Tanks

In light of there being horizontal tanks, there must also be vertical tanks. Much like their long counterpart, these taller aquariums have the bulk of their surface area in their vertical access.

This style won’t take up the whole of a desk, but they can be as tall as your average wall in a home or office.

Some fish prefer to swim in the depths of a tank, and vertical tanks provide the varied dimensions in order for those fish to feel more at home.

As a plus, this design can save room in an apartment or home that lacks space square-foot-wise, but which boasts of average or exceptionally tall ceilings.

Fish Tank Decorations to Avoid

With all of the basics out of the way, you can finally move forward with deciding what kind of decorations to put in your tank.

Some of the following are decorations made of materials you’ll want to avoid – but don’t feel limited! By concentrating on the health and safety of your tank, you’re doing more to ensure that your fish stay happy and healthy.


Given the popularity of making toys out of plastic, both for humans and for fish, you may find yourself asking, “Is plastic safe for fish tanks?” Or, rather, “How can it not be?”

While the majority of fish accessories are made out of plastic, you’ll have to take care when making these sorts of purchases or when finding plastic accessories to include in your tank from around your home.

Avoid putting your children’s toys in your fish tank, because even if they’re suitable for child’s play, the plastic may have toxins in it that are detrimental to the health of your fish.

Always be sure to check the labels of fish-specific plastic toys, as some may contain warnings for certain species or aquarium conditions (such as salt water).

Ceramics, Especially Homemade

There’s always a risk that any ceramics you have around your home, like old plates, home-fires cups, and so on, may carry chemicals in them that, like plastic, can damage your fishes’ health over time.

No matter how aesthetically pleasing a ceramic mosaic may be in your tank, you’ll want to ensure that you purchase one from the pet store instead of DIY-ing a potentially dangerous tank accessory.

Untreated Wood or Rocks

While it may be tempting to put accessories you find in the wild into your fish tank, it’s highly recommended that you don’t.

Regardless of how money-conscious the decision may seem, wild or untreated wood, rocks, mosses, and so on can carry mites and minerals that will change the chemistry of the water in your tank, threatening the preferred pH level that your fish live in.

Maintaining that pH is exceptionally important, as variations in the acidity and baseness of the water will absolutely threaten your fishes’ health.

Likewise, any bacteria, insects, or mites that you inadvertently introduce into your fish tank can bring indefensible viruses to the water and send your pets into a distressed state.

Wild Sand

Similarly, you’ll want to invest in a certifiably safe substrate for your tank, instead of bringing wild sand into your fishes’ habitat.

Again, it may seem like a money-conscious decision to work with what nature has provided, but you’ll need to be considerate not only of your breed of fish but of their tender immune systems.

Sand from a number of random beaches may be fine for wild fish to live near or above. However, it’s always possible that said sand will be utterly incompatible with the fish you intend to raise in a to decorate a fish tank with household items

This is namely because the majority of tank fish come from natural habitats that are overseas, or whose natural habitats have a particularly complex ecological, chemical make-up that wild sand will disrupt.

Furthermore, much like with wood or rocks, wild sand can introduce mites or bacteria to your fish that will compromise their health.

Wild-Found Shells

Wild-found shells are equally unhealthy for your fish. Be sure that any shells or coral you bring into your fish tank have been treated, or that, at least, the fish with whom these materials share space are saltwater fish as opposed to freshwater fish.

Seashells in aquariums may seem like a natural fit, but in fact, you’ll be better off finding some that have been treated as opposed to any that you would find in the wild.

Sharp Glass

While most glass toys or tank accessories can be safe for your fish to interact with, you’ll want to take care to avoid introducing sharp glass into your tank.

No matter how squishy and bounce-able they appear, fish are quite delicate. If they brush up against sharp glass by accident, it’s entirely possible that they’ll cause themselves irreparable damage.

Try to keep your glass accessories comfortably rounded or unpainted in order to save your fish from themselves.

Anything Degradable or Edible

You may think that, like with dogs and cats, introducing food-oriented stimuli to your fish tank will be a good thing. However, you should avoid contaminating the water with any toy materials that will degrade over time or that are edible.

Toys that degrade will permeate the tank water and clog your filters, while edible toys will disrupt the diets of your fish and, again, dirty your tank water more-so than food pellets on their own.

What are your favorite fish tank decorations?

Leave a Comment