Will Acrylic Paint Wash Off If Used Inside an Aquarium?

One of my neighbors bought a new aquarium last month. She gathered a few stunningly beautiful pieces of driftwood and stones to put them inside with fish.

But before putting them inside the aquarium, she wanted to color them beautifully.

She called me and asked if she could color them with acrylic paints she already had in her home.

Will the paint stay there, is it waterproof enough, and if not, what can she use to make the paint waterproof?

She had many questions, and I thought to jump in and write a detailed post of what I advised her.

Hopefully, it can help many users who want to know about aquarium-safe paint for decorations. So, let me start with the main question first…

Does Acrylic Paint Wash Off with Water?

First and foremost, acrylic paints aren’t waterproof and weather resistant.

Although they are water-resistant after they are dried and have stuck to your painting surface, they can still be washed off if exposed to water for a long.

Especially if you are using warm water in your aquarium (which you must be in winter), the wet paint will be more likely to bleed and run.

So, if you want to use acrylic paint in your aquarium, you will need a waterproofing sealer to make it work.

I’ll tell you more about that in a minute.

But before we talk about the sealer, let me give you some more information on acrylic paints.

What is Acrylic Paint – Why Use it in Your Aquarium?

Acrylic paint is a fast-drying water-based paint made of pigment suspended in acrylic polymer emulsion.

An acrylic polymer emulsion is a cross-linked network of interconnected polymer chains dispersed in water.

The polymer chains are formed by the reaction of an acrylic monomer and a polymeric material.

The water evaporates when the acrylic paint dries, and the acrylic polymer chains interlock to form a solid film.

That’s the reason acrylic paints are water-soluble but become water-resistant when it dries.

Depending on how much the paint is diluted (with water) or how thickly it is applied, the finished product can range from very soft to very hard.

The advantages of using acrylic paint in an aquarium are that it is:

• It is easy to find, cheap and non-toxic
• It can be easily removed if you don’t like the way it looks
• It’s vibrant and can add a beautiful pop of color to your aquarium decorations submerged in water

You can use the paint on plastic, stones, rocks, fabrics, and even on the inside of the aquarium glass surface to decorate your fish tank beautifully.

But as I just said, the paint (even when it’s dried) will gradually flake off whatever they are painted on.

How Safe is Acrylic Paint on the Fish Tank?

The harmful chemicals sometimes produced in the water can be hazardous for your fish and other aquatic creatures.

Even though the paint was initially non-toxic, the flaked pieces of paint that break apart can be poisonous to some fish if they view it as food and consume it.

So, what can you do to make the paint stay on the aquarium decorations and not flake off?

Use a waterproofing sealer!

Steps for Using Acrylic Paint to Paint Aquarium Decorations

If you decided to use acrylic paint to add color to your aquarium decorations, here are the steps you need to follow:

Step 1. Prepare the Work Area

Start by preparing the area you will be painting. Cover the floor around your work area with a drop cloth or old newspaper.

This will make cleanup more effortless if you accidentally spill or drip some paint.

Step 2. Clean Aquarium Decorations

Clean the surface of the decorative aquarium pieces (you intend to paint) with soap and water to remove any dirt, dust, or grease.

Pieces like driftwood can have algae and other growths on them that need to be scrubbed off before painting.

So, clean and disinfect them nicely using a bleach solution, vinegar, or soda water.

After cleaning, rinse the pieces and allow them to dry completely.

Step 3. Prime the Surface (optional)

If you are painting with a light color over a dark one, or you are painting sufaces like plastic or glass, you will need to prime the surface first.

This step is necessary to improve the acrylic paint’s adhesion to the surface and prevent peeling.

For priming, you can use an acrylic-based primer or white latex paint. Apply the primer using a brush, roller, or spray can, following the manufacturer’s instructions.

Step 4. Choose Your Colors

Now, it’s time to choose the colors of aquarium-safe acrylic paint you want to use.

You can use a single color or mix different colors to create unique shades on the pieces of rocks and toys you will be using in a fish tank.

Step 5. Begin Painting

Once you have chosen the colors, it’s time to start painting the objects with

fish-safe paint that’s nearly waterproof. Begin by painting the larger areas first and then move on to the smaller ones.

You can use a paintbrush or a sponge to apply the paint to the surface. Remember to apply the paint in thin layers, as thicker layers will take much time to dry.

Step 6. Let it Dry and Apply Additional Coats

Let the acrylic paint layer dry to the touch before moving on to the next step.

This usually takes about 30 to 40 minutes, but it can take longer, depending on the thickness of the paint.

If you want, you can use a hairdryer to speed up the process by blowing warm air over the painted surface.

Once the first layer of paint is dry, apply 2-3 additional layers in the same manner by repeating steps 5 and 6.

Let the first layer dry completely before proceeding to the next coat.

Step 7. Apply a Final Top Coat of Paint to the Objects

Now it’s time to apply a final topcoat of acrylic paint to the painted surfaces to prevent the color from fading – and to make the paint more resistant to peeling.

Do this nicely and evenly. Once coated, allow it to dry and cure completely for about 48 hours.

Usually, it takes 24 hours to cure the acrylic paint, but since you will be submerging the painted objects in the water, I would recommend waiting at least 48 hours to be on the safe side.

TIP: To make your stones or other objects more beautiful, you can sketch or print out images you like, cut them out, and then use them as a stencil to paint over.

How to Make Your Acrylic Painted Objects Waterproof – What Sealer to Use?

A waterproofing sealer varnish will help make your paint job last longer by holding the paint onto the surface and making it more resistant to water.

You can find many waterproofing sealers in the market for interior and exterior use. But ensure you get the one that is safe for aquariums.

Some of the most popular brands that make aquarium-safe waterproofing sealers are Plasti Dip and Krylon Fusion.

I had worked with Krylon Fusion All-In-One Spray before and recommended the same to my neighbor for sealing her fish tank decorations that included rocks, fake plants, and plastic toys.

Krylon Fusion is aquarium safe (above and below the waterline), but it isn’t as good to hold on to the glass of fish tanks.

So if you want to use a sealer for aquarium background glass (from the inside), you can use a Plasti Dip.

Once you have the waterproofing sealer ready, you can apply it by following these steps…

• Using a spray-on sealer or brush-on sealer, apply an even coat of sealer to the painted area.
• Let the waterproofing fish sealer dry entirely according to the manufacturer’s instructions.
• After it has dried and cured, you can submerge the decorated rocks or toys in your aquarium.

Related FAQs

Which paint can I use for the cement fish tanks?

Cement fish tanks are standard in many homes. If you have one of these, you’re probably wondering what paint you can use to spruce it up.

I think two-part epoxy resins that dry clear are best for painting cement fish tanks or concrete outdoor aquariums.

You can find these types of resins at most hardware stores or online. However, you’ll want to ensure that the resin is non-toxic and safe for your aquariums before using it.

Can acrylic paint inside the aquarium kill my fish?

Acrylic paint will not kill fish and other aquatic animals unless they consume it.

But I would recommend that you don’t use paint inside the aquarium as it can be harmful to the fish if they accidentally ingest it.

If you are using, get premium quality, non-toxic acrylic paints and sealers that are fish safe.

How do I remove acrylic paint from my aquarium glass?

If you want to remove the paint from your aquarium glass or expensive decorative objects, you can do so by using a razor blade or a putty knife.

First, scrape off most of the paint and then use a glass cleaner to remove the remaining paint.

The bottom line

Painting inside the aquarium and the decorative objects you put inside is a fun project that can be completed on the weekend with your kids.

Just make sure that you use non-toxic and safe materials like acrylic paints that won’t harm your aquatic animals.

Also, ensure the objects are correctly sealed to make the paint waterproof when you submerge them in an aquarium.

Have fun painting!