DIY Aquarium Rock Slime for Kids

Looking for a fun new textural element to add to your homemade slime? This DIY aquarium rock slime recipe is a great way to shake things up! It’s super simple to make, and because it’s activated with contact lens solution rather than Liquid Starch, it’s also safer for your child’s skin. All you’ll need to make this slime is a few basic ingredients and 10 minutes of free time!

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Homemade slime has become something of a staple at our house. It’s such an easy activity to prepare and it always keeps our kids occupied for quite a while!

It’s also really easy to customize when you feel like experimenting with different textures. Whether you’re mixing in some leftover water beads or adding shaving cream to create fluffy slime, you’re sure to find a texture to please every child!

And if your child is still too young for regular slime, you can even make it out of edible ingredients!

Warning: This particular slime recipe is not taste-safe and it contains small rocks that could pose a choking hazard, so it’s not meant for very young children. Since I was making this slime for our three- and four-year-old to play with, I also whipped up a batch of Taste-Safe Psyllium Husk Slime so that our one-year-old could feel like she was part of the fun!

How to Make Aquarium Rock Slime

Required Ingredients

Here’s what you’ll need to make this fun textured slime at home:

Note: The contact lens solution you use must list “boric acid” and “sodium borate” as ingredients in order for the chemical reaction to occur. We bought ours at Walmart and carefully compared ingredients and prices before choosing the brand pictured below.

Contact Lens Solution for Slime Containing Boric Acid and Sodium Borate

Step-by-Step Instructions

1. Combine Water and Glue

Combine ½ cup of clear glue and ½ cup of water in a small bowl. The added water is what makes the slime so stretchy!

2. Add Colour

Add a few drops of liquid watercolour paint or food colouring to the mixture. We decided to make ours blue to match the aquarium rocks. We added about 6 drops, but feel free to add as few or as many as you like.

3. Add Baking Soda

Mix in ½ teaspoon of baking soda.

4. Add Contact Lens Solution

It’s time to add the slime activator! Start with 1 tablespoon of contact lens solution and stir until well combined.

You may notice the mixture starting to solidify a little, but 1 tablespoon likely won’t be enough to fully activate your slime. You’ll probably end up needing somewhere between 1 tablespoon and 1 ½ tablespoons.

Once I’ve added the initial tablespoon, I usually add one small squirt at a time, mixing well between each addition. Don’t add too much at a time or your slime will become rubbery! (You can fix this by adding warm water and gently working it in with your hands, but it’s much simpler to prevent this issue altogether by adding the activator slowly.)

I usually stop adding contact lens solution when the mixture stops behaving like a liquid and starts sticking to the sides of the bowl, as pictured below.

I always try to use as little contact lens solution as possible because this keeps the slime nice and stretchy!

6. Knead Slime

Once you’ve added enough activator, it’s time to knead! The slime will be very sticky initially, but the more you knead the slime, the less sticky it should become. Don’t be surprised if it takes a lot of kneading!

If ever your slime is simply too sticky to knead, you can always add a little bit of extra contact lens solution to your hands to make things easier.

Note: If you like to wear rings, please remove them before kneading the slime. If you don’t, the slime could get into any crevices and cause a rash on your finger due to prolonged exposure—I speak from personal experience!

6. Add Aquarium Rocks

Once the slime stops sticking to your hands, you can add the aquarium rocks. I only add the rocks once the slime is fully kneaded because it would be a lot harder to knead with the rocks already in it.

You can add as few or as many rocks as you like, but ½ cup is a good starting point. Simply pour them onto the slime, then fold them in with your hands and gently knead it.

Once the aquarium rocks are well integrated, it’s time to play! The rocks shouldn’t pop out much, but there’s a possibility that they might, so I recommend supervising extra carefully to ensure you don’t end up with little rocks everywhere.

Our four-year-old particularly loves this type of slime! We made it for the first time several months ago and she’s been asking to make it again ever since the old batch lost its elasticity!

Tip: Leave out some small containers and (kid-safe) tweezers for your child to play with. Our four-year-old loves to pluck the little rocks out with tweezers and place them in a bowl next to the slime!

Related Contact Lens Solution Slime Recipes

Looking for more DIY slime recipes that you can make using contact lens solution? Check out these recipes: 

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The Craft-at-Home Family