Decorating Your Fish Tank: Dos and Don’ts

Written by: Alex more

isharkbait is a marine biologist, aquarist, lover of animals, and an experienced veterinary assistant.Contact Author

Where to Begin?

You have your perfect tank, complete with all the bells and whistles of filtration. You have your water quality test kit ready. You have a list of fish you would like in your collection. So, how are you going to decorate your aquarium? Believe it or not, this is where a lot of people run into problems. Sometimes they get so excited about all the cute decorations at the pet store that they overcrowd the bottom of the tank. This is no good. Not only will this make doing tank maintenance harder (just think of trying to gravel wash all that), but it also it looks tacky. With that in mind, how do you pick out decorations for your tank? This is the time to be creative, as the sky is truly the limit.

Work From the Bottom up

The first step in decorating your fish tank is choosing which substrate to use to cover the bottom.
The first step in decorating your fish tank is choosing which substrate to use to cover the bottom.

The first thing you want to consider is what kind of substrate to use. There are many different options. Do you want a sandy bottom? What about small gravel, or large? You can even use small stones. Do you want to use glass pebbles? Do you want the tank to be colorful or more natural?

The most important thing to consider when choosing a substrate is your fish. Sometimes the type of fish you want will dictate what kinds of substrate you have to use. If you want fish like eels or knifefish, you need to have a sandy bottom. Eels will spend most of their time on the bottom, and if you have a rocky substrate, they will rub their bodies raw, which is bad for them. If you are considering a freshwater ray, then you need to have a large bottom with sand. They will bury themselves in the sand, which would be nearly impossible for them to do safely in a tank with gravel as the substrate. Sand will also give your tank more of a saltwater feel, which many people desire.

However, sand does have some downsides. If you plan on doing gravel washes, which you should strongly consider, sand can make them more annoying. Since the sand is smaller and lighter than gravel, it tends to travel higher up the tube. It also tends to end up in whatever you are using to collect your waste water. This means that you will need to replace sand more often than you would have to replace gravel.

Gravel and stones are popular choices for freshwater tanks. They create a natural look for the tank and they are easy to clean. They are a better alternative to colored glass pebbles which, however pretty, are not always the best choice for a large fish tank. Glass pebbles aren’t necessarily bad for your fish, they simply do not provide as much surface area for good bacteria to colonize. You need good bacteria to keep the nitrogen levels in your tank in check. Glass pebbles over time will break down, as is natural, and gravel will erode as well. However, the glass pebbles will have sharper edges whereas the gravel will just become finer. Glass pebbles are pretty, but they are just for show. It would not be harmful to have a few of them scattered throughout the bottom of the tank, as they will add some color. Just be sure to change them out once they begin to show signs of wearing down.

You need to make sure that everything you put into your tank is properly rinsed—and that includes your substrate. Sometimes you need to rinse it a few times to get all of the dust and debris out.

Plants: Live or Fake?

Fake plants can lend your tank a splash of colors. If you are using live plants, make sure that they are a species that can be fully submerged in water.
Fake plants can lend your tank a splash of colors. If you are using live plants, make sure that they are a species that can be fully submerged in water.

Plants are a very popular decoration in many aquariums. Some people like them because they add color to the tank. Some add them because plants are found in many freshwater environments and can give the tank a more natural feel. If you go to the pet store, you will see a wide array of choices when it comes to aquarium plants.

The vast majority of home aquariums use plastic plants in place of live ones. Why? The plastic plants are often more colorful than real plants, coming in colors that are not found in in nature. They are also easier to maintain since they cannot die. And, like real plants, they offer the fish a place to hide.

However, real plants can offer systems something fake plants cannot: They can help improve the water quality of your tank. How is this? Plants need to use nitrogen and in an aquarium they are able to use the fishes’ waste products. This keeps the levels low in the tank, which is a great bonus. Plants also use CO2 (carbon dioxide) for their respiration and give off O2 (oxygen) as a waste product. This is great for home tanks, as carbon dioxide build-up can be toxic and stable oxygen levels not only help your fish breathe, they can help maintain a stable pH level.

Of course, fake plants do have their own advantages: They don’t drop leaves or die. Dead leaves and plants decompose, which can cause nitrogen levels in the tank to spike. This spike can stress the fish and, if it is high enough, could potentially lead to death.

Fake plants can be used to add color to fish tanks
Fake plants can be used to add color to fish tanks

Do you prefer live or fake plants in your home aquarium?

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Adding Decorations

What other decorations are safe for your tank.
What other decorations are safe for your tank.

The sky is truly the limit when it comes to adding decorations to fish tanks. You can even get a miniature replica of Bikini Bottom or Stonehenge if that is what you are into. Pet store shelves are lined with fake rocks, corals, and sunken ships, as well as many other oddities. These items have been specifically designed to be in fish tanks. This means that the materials used will not deteriorate when submerged in water for long periods of time.

There are a few things to keep in mind when picking out decorations for your tank. You need to know exactly how big the bottom of your tank is. You also need to keep in mind anything else you might already have. Are you adding plants? How many? The last thing you need to keep in mind is exactly what you want your tank to look like. Many people often go overboard when it comes to picking out decorations for their tank. It can be really easy to do, and let’s face it, it’s really fun to pick things out for your tank. Just keep in mind how much space you have to work with. Do you really have room for that sunken ship, fake corals, and the giant treasure chest? Sometimes simpler is better. One large piece and a couple of smaller pieces are all you need, especially if you are adding plants.

You might be tempted to add real coral and driftwood. This can be dangerous. You do not want to add any diseases or parasites to your tank. Also disturbing coral reefs is illegal in many places, not to mention extremely frowned upon in the aquarist and diver communities. Since I do not support this practice, I will not discuss it further. But, I will say this: Live coral loses its color once it dies, and wouldn’t you rather have fake coral that has a realistic color instead of a white mass in your tank?

Sometimes people are tempted to add things that have not been designed to go in fish tanks. You would be surprised what some people want to use as decoration. Sharp edges, concrete, copper, and plastics that have been painted should not be put in your fish tank. Why? These items will cause problems. Copper is toxic to fish and concrete is going to leach chemicals into your tank. Sharp edges can harm your fish and should always be avoided. Paint can flake off or poison your fish. If you ever put something in your tank and notice that it seems to be flaking or the paint is disappearing, remove it immediately.

When in doubt, do not add it to your tank. It is better to be safe than sorry. After all, do you really want to endanger your fish just for the sake of having costume jewelry in your tank? Always keep in mind that no matter what you add, you want to rinse it thoroughly before it goes in.

Things That Don’t Belong in Fish Tanks

Ceramics, wood, rocks, glass, plastics, coins, shells and corals may not be safe decorations for your tank.
Ceramics, wood, rocks, glass, plastics, coins, shells and corals may not be safe decorations for your tank.
  • Ceramics (if you cannot eat off it, don’t put it into your tank; they can leach chemicals and heavy metals)
  • Wood (unless it was purchased at a pet store and has been pretreated)
  • Rocks (some rocks have minerals that you do not want in your tank)
  • Shells and corals (in freshwater systems, they will add calcium that the system does not need)
  • Some glass (glass is safe unless it has sharp edges or has been painted)
  • Plastics (general rule of thumb is if it smells like plastic, it doesn’t go in a fish tank)

Cleaning Your Decorations

All decorations will need cleaning at some point. Here's how.
All decorations will need cleaning at some point. Here’s how.

No matter what you use for decorations, except for live plants, you are going to need to clean it at some point. You are going to need some basic tools to clean your tank and decorations. Scrub brushes with bristles, soft pad scrub pads, and a gravel wash kit are a few of the items that I would recommend. Be sure to get items that go with your tank, and keep in mind that acrylic scratches much more easily than glass, so never use a rough brush or pad on an acrylic tank.

Scrub the algae off of the sides of the tank.
Scrub the algae off of the sides of the tank.

The first thing you want to do is scrub off any algae or gunk from your decorations and the walls of the tank. The hard bristled brush is good for scrubbing the decorations and the soft pads, especially with the long handles, are good for the walls. Once you have scrubbed the algae, it is time for the water change. Cleaning the substrate is easy, and you remove your water at the same time. Two birds with one stone, what is better than that? A gravel wash tube is typically an acrylic tube with a flexible hose that goes into a bucket. The acrylic tube and hose use suction to shake up the gravel and pull dirty water, detritus, and poop through the hose and into the bucket.

You can change your water and clean your substrate at the same time.
You can change your water and clean your substrate at the same time.

How often you should clean your gravel depends on several factors. How many fish do you have? Do you often overfeed your fish? Do you have live plants that lose leaves? Even if your tank has excellent water quality, you should consider doing small gravel washes weekly to remove the excess food, poop, and detritus.

Cleaning the decorations in your tank keeps them bright and the tank healthier. It is also very satisfying to see all the gunk that you remove from the gravel of your tank.

How to Gravel Wash

Methods Behind Gravel Washing


Many hobbyists opt to have a background on their tank. There are many different options for backgrounds. They come in different colors and patterns. Really, there are no wrong choices, so you can do whatever your heart desires. If you want a plain blue background, go for it. If you want a sunken ship in your background, have at it. If you want a picture of the castle at Disneyland, knock yourself out. If you don’t want a background, you don’t need to have one. Some people just don’t like the look of the wall behind the back being visible from the front of the tank. It is really a matter of personal choice. Personally, it doesn’t bother me to see the wall behind my tank, but when I do use backgrounds I make sure that I hide the tape well. I can’t stand being able to see the tape; I feel it makes my beautiful tank look tacky.

On a side note: I have never seen the Disneyland castle as a background option at a pet store. But, if you happen to have a picture (and if you don’t, the Internet is a lovely place), you can simple have a picture printed to the correct size and laminated. Why laminated? Think about it. At some point, no matter how careful you are, you are going to get water on the background.

Questions & Answers

  • Question:My wife likes to rearrange the layout of our aquarium every week. It seems to make one of our African Cichlids a little more aggressive. Is it ok for her to keep doing this, or should we leave the stuff alone?Answer:Changing the layout of your aquarium is a good way of adding enrichment. I did it all the time when I worked at an aquarium. For some species of fish, a place to hide is important. For some fish they want a territory to defend. If it is having a negative effect, I’d see if the fish seems to be protecting a particular area or decoration. If that seems to be the case, I’d leave that area alone and rearrange other decorations. Helpful 28
  • Question:Is Javan Moss unhealthy to humans?Answer:Javan Moss is a very commonly used plant for aquarium decoration and typically used with cichlid tanks. I doubt that it is unsafe for humans since it is widely used, but it is possible that someone could be allergic to it. If you are concerned about an allergy you can wear gloves when you handle it. Helpful 1
  • Question:I just got a fish tank and put everything in it. Now that my fish is in the tank, can put more rocks in it?Answer:When adding rocks to an established tank, you’ll need to be careful. Make sure that you have already cleaned the rocks – usually a rinse with hot water is fine. I would wait until you need to do a water change to add the rocks and I would do it very slowly. If you’re talking about gravel, I would add it by the cupful and take the cup of gravel directly to the bottom of the tank to deposit it. If you are adding larger rocks for decoration, I would place them slowly by hand. Adding new rocks and gravel at a water change makes it easier to move things around the way you want them. Remember, fish can stress easily and you want to make this process as easy as you can for them. Helpful 16
  • Question:What bottom does a beta fish need?Answer:They aren’t picky fish for…Helpful 1
  • Question:Where should I buy a fish?Answer:That depends on what is available in your area. If possible go to a local pet store and see where they source their fish. Are they captive-bred or collected from the wild? If there isn’t anything in your area, see if a major chain pet store has good looking fish. Are they healthy? How far did the fish have to travel to get to the store? I would be hesitant to buy fish online since I can’t see them before I buy them. Helpful 3

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