Aquarium safe glue is important for the safety of your tank

Aquarium Safe Glue: Aquarium Adhesive Options

Keeping the decorations and plants in your fish tank where you want them can be challenging. Using weights, string, and plant anchors only add to the frustration. Aquarium adhesive is often the easiest and fastest way to secure them, but many glue types leach harmful chemicals into your water and are unsafe for fish. Your elementary school glue stick won’t work here. Aquarium-safe glue is often the best option because it’s safe for your fish and plants and can permanently adhere your decor to your glass. Our favorite aquarium-safe and reef safe glue is Seachem Reef Glue.

We’re going to discuss the eight best aquarium-safe glue options below so you can get started decorating your tank safely right away.

Best Aquarium-Safe Glue Options:

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What is the Best Aquarium-Safe Glue?

Our favorite glue for tank decorating overall is the Seachem Reef Glue. It forms a strong bond instantly, can be applied underwater, and is thicker than a super glue to help reduce mess and provide a clean, natural look when decorating.

What are the Aquarium Adhesive Types?

There are four different kinds of adhesive that are safe to use in fish tanks, each with its upsides and drawbacks.

Super Glue

Most people are familiar with how quickly super glue bonds, and aquarium-safe options cure just as quickly. The brands made for fish tanks have a cyanoacrylate (CA) base, making them safe for fish and plants in the water. Super glue is often the cheapest option. Benefits of super glue include:

  • Affordable
  • Familiar and easy to use
  • Long-lasting hold


Not all silicone adhesives are tank-safe, but those that are maintain a strong bond and won’t leach harmful chemicals into your water. Most of them dry clear, but some have color options if you prefer. They need to be applied when your tank and decorations are entirely dry, but once cured, they maintain a permanent, flexible bond. Advantages of aquarium safe silicone include:

  • Permanent and flexible hold
  • Works well with glass
  • Doesn’t leach chemicals in aquarium water
  • Different colors option


Epoxy offers a high-strength bond that can form in dry or wet conditions, making the application process easy. It dries clear, so it won’t detract from the appearance of your aquarium. It’s entirely safe for fish and plants after it cures. Epoxy is a great choice because:

  • Easy application process
  • Great for repairing pipe leaks
  • Strong bond in both wet and dry conditions
  • Dries clear


Liquid cement is a thick, clear adhesive that you can use to fill in large gaps between decorations that aren’t flat. Provided you choose one that’s safe for use around fish and plants, it’s an excellent option for gluing rocks or other irregularly shaped objects in your tank. Liquid cement can be a great option as the best glue for aquascaping rocks. We love cement as an aquarium adhesive because:

  • Great for filling gaps between decorations
  • Excellent for holding rocks in place
  • Thick adhesive with strong bond

The 8 Best Aquarium-Safe Glue Options

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1. Seachem Reef Glue

This is a cyanoacrylate glue that forms a solid bond once cured. It cures in just a few seconds, and you can apply it in dry or wet conditions.

The formula is significantly thicker than traditional super glue, which reduces mess and makes the application underwater straightforward. It isn’t the best option for gluing irregularly shaped objects like rocks or driftwood.

It dries clear and won’t detract from the aesthetic of your tank.


  • It comes in tubes with a small tip for easy application
  • The thicker formula reduces mess and improves accuracy


  • You can apply it underwater or in dry conditions
  • It dries clear


  • It’s not the best for filling gaps between non-flat objects
  • The small containers are not ideal for large jobs

2. Oceans Wonders Reef Glue Gel

This is a cyanoacrylate glue that cures rapidly and creates a strong bond. You’ll need to apply it in dry conditions for the best seal possible, but it could be used underwater if necessary.

It comes in a small container with a thin tip for precise application. The formula is thick, making it easy to control where the glue gets placed.

This glue dries entirely clear and won’t cloud your tank or detract from the visual appeal of your decorations.


  • The container has a small tip for precise placement
  • The thick formula gives you control when applying


  • It forms a strong, permanent bond
  • It dries clear and won’t cloud your water


  • It’s somewhat expensive
  • It’s most effective when applied in dry conditions

3. SILA-SEAL Clear Professional Grade 100% RTV Silicone

This is a silicone adhesive that creates a robust, flexible seal when it cures. It can take several hours to dry thoroughly.

It’s thick, so it’s an excellent option to keep abnormally-shaped decorations like rocks and driftwood in place.

It dries clear and won’t cloud your tank, but you won’t be able to paint it. It may highlight algae after some time and get discolored.

It comes in large bottles that are better for larger jobs but aren’t ideal for precise application.


  • It comes in large bottles that provide excellent value for the money
  • The thick formula makes it easy to apply any size or shape of decoration


  • It creates a robust, flexible bond
  • Excellent silicone sealant
  • It’s great for larger jobs


  • The broad tip makes precise placement challenging
  • You can’t paint it
  • It highlights algae over time

4. MarineLand Silicone Squeeze Tube

This silicone adhesive is thick and great for filling gaps or gluing round or irregularly shaped decorations.

The bond it forms is strong and permanent, but it needs to be applied and cured in dry conditions, making underwater decorating impractical. It can take several hours to cure.

It comes in a small tube that is relatively expensive for the amount you get, and the applicator isn’t very precise.

It’s 100% silicone, so it’s entirely safe for fish and plants.


  • The thick formula makes gluing irregular surfaces straightforward
  • It becomes inert once cured and won’t harm your tank inhabitants


  • It’s excellent for large gluing applications
  • It creates a strong, permanent bond


  • It’s relatively expensive
  • It takes several hours to cure
  • It needs to be applied in dry conditions

5. Aqueon Silicone Clear

This is a silicone glue that cures somewhat slowly. It needs to be applied to dry surfaces and allowed to cure fully before being exposed to water.

It dries entirely clear and won’t cloud your tank. However, it can attract and draw attention to algae, potentially detracting from your aquarium’s aesthetic.

It has a somewhat thick applicator tip, which makes precision impractical. As such, it’s best for large gluing jobs.

The thick formula makes it ideal for filling gaps and adhering non-uniform surfaces.


  • Thick formula fills in gaps and makes for easy gluing of non-flat surfaces
  • It comes in large tubes ideal for bigger jobs


  • It creates a permanent, waterproof bond
  • It dries clear


  • It dries somewhat slowly
  • It can’t be applied underwater
  • It can attract and highlight algae

6. Instant Ocean HoldFast Epoxy Stick

This is an epoxy that forms a solid bond and can be applied in dry or wet conditions.

It acts like clay that you knead and mold into shape and then compress between your surfaces. It takes about ten minutes to dry, so it’s not as rapid as CA glue. It dries white, so it may be noticeable in your tank.

You can use small pieces for precise application, but it needs to be molded and can cause some minor skin irritation.


  • It turns white once kneaded so that you know when it’s ready to use
  • The clay-like consistency makes application effortless and clean


  • It can be used in dry or wet conditions
  • It’s an excellent option for small and large jobs and on irregular decorations


  • It may cause some minor skin irritation
  • It isn’t as quick to dry as CA glue
  • It doesn’t dry entirely clear

7. Two Little Fishes Marine Reef Rock Putty

This is an epoxy that acts like clay. You can knead and form the exact amount and size you want for precise application and minimal waste.

It dries the color of coral, so it’s really only suitable for use on similarly colored decorations. However, it creates a powerful, permanent bond and can be used on any kind of surface.

It can be applied in dry or wet conditions, making application effortless in new or existing tanks.


  • The moldable formula makes application precise and straightforward
  • The epoxy can cure underwater


  • It can be used on uneven surfaces
  • It’s effortless to use


  • It dries the color of coral, so it’s most useful on reefs
  • It may cause some minor skin irritation

8. Loctite 1919324 Marine Epoxy

This liquid epoxy dries relatively quickly but not as fast as CA glue.

It dries clear, so it won’t detract from your tank’s aesthetic.

You can apply this in dry or wet conditions. However, the double tip and the two-step application process make using it a bit challenging. It’s not ideal for precise gluing.

This only comes in small bottles, and it’s relatively expensive. It’s suitable for small, underwater jobs, but it will be prohibitively expensive for bigger applications.


  • The two-step process ensures it won’t dry in the tube
  • The formula allows for underwater curing


  • It dries in just a few minutes, giving you some time to correct mistakes
  • It dries clear and won’t be noticeable in your tank


  • The double tip makes application a bit complicated
  • It isn’t ideal for precision gluing
  • It’s fairly expensive

Characteristics of Aquarium-Safe Glue

Aquarium-safe glue needs to be formulated for use underwater, which means it should be inert on wet or moist surfaces. This property will allow for a strong bond that will stand up to exposure to water.

Aquarium using the best aquarium safe silicone to seal the edges

It doesn’t always have to dry clear, as it may not be visible under decorations. However, it shouldn’t cloud your water over time.

Lastly, an aquarium-safe glue shouldn’t leach chemicals into your water that could be dangerous for fish or plants.

How to Use Aquarium Adhesives

The application process will depend on the type of adhesive you purchase.

Super Glue

Superglue or CA glue can be applied using a squeeze tube or flexible container. The glue comes out of a thin tip that should be directed toward your surface. It can be applied underwater or on dry decorations.


You can apply silicone either with a squeeze tube or caulk gun. It should be placed only on dry surfaces and allowed to cure before being exposed to water.


Epoxy often comes in a clay-like form. You can knead and mold a piece into shape and then compress it between your two surfaces. Hold for several minutes in dry or underwater conditions.


Liquid cement comes in a squeeze tube with a small applicator tip. Apply it in dry conditions and allow it to cure for several minutes before exposing it to water.

Can You Glue Aquarium Plants?

Yes, you can glue aquarium plants to rocks, driftwood, or substrate. Depending on the aquarium aesthetic you’re trying to create, you can get very creative with aquarium plant placement.

Multiple adhesive types can be used with plants but the most common is super glue. Super glue is thick and doesn’t spread everywhere accidentally. It creates a strong bond between the plant and the rocks (or driftwood) where you anchor the plant.

If you want to glue an aquarium plant to a rock, here are our recommended steps:

Given below are the steps to glue aquarium plants to rocks:

  1. Rinse and scrub the rocks to remove dirt and organic matter.
  2. Use a bleach solution to remove any remaining unwanted organic matter. Rinse them thoroughly with running water afterward to remove the bleach.
  3. Boil the rocks for 10-20 minutes to kill unwanted pathogens.
  4. Get your glue ready and pierce the top cap if you haven’t already.
  5. Remove the plant from its pot and run water over the roots to clean them. Once the roots are clean, find the rhizome (underground plant stem). Rhizomes are how the plant will generate a new shoot and root system.
  6. Find a good part of the rock to place the plant (typically a flatter area where it can easily adhere).
  7. Dry the plant’s roots using a paper towel.
  8. Apply a layer of glue to the rock where you want to anchor the plant.
  9. Press both the roots and the rhizome on the rock’s surface where you have applied the glue. Hold everything together for a few minutes to give the glue time to bond
  10. Try to work quickly so that you complete the process in 10-15 minutes to avoid shocking the plants.
  11. Once the glue is bonded, add the rock-plant combo to your tank to create a beautiful aquascape.

How to Glue Aquarium Rocks Together

Thinking about anchoring some aquarium rocks together with an adhesive? These are the steps we follow before gluing:

  1. Consider the type of rocks needed in your aquarium. Slate, reef rock, porous lava rock, seiryu stones, and smooth river rocks are all options.
  2. Rinse and scrub the rocks to remove dirt and organic matter.
  3. Boil the rocks to kill unwanted pathogens. This step is especially important if you’ve sourced your rocks from nature.
  4. Use a bleach solution to remove any remaining unwanted organic matter. Rinse them thoroughly with running water afterward to remove the bleach.
  5. Dry the rocks before adding any adhesive.
  6. Apply adhesive between the contact points of the rocks. Hold the rocks in place until the adhesive bonds and sets. Time required to set will differ by adhesive type.
  7. You can create multiple types of structures for your tank – sloping structures, caves, underwater forests, etc.
  8. Before adding the rock structure to your tank, prepare a substrate base using sand or gravel. We don’t recommend placing the rocks directly on the glass.
  9. Place the rock structure in your tank and try to keep it away from all glass, in case a fish bumps it into the side of the tank.
  10. You will want to make sure you leave sufficient space between the rocks and other features to allow for sufficient water flow. This helps oxygenate the tank and wash out waste.

Aquarium-Safe Glue FAQs

Is Glue Gun Glue Safe for Aquariums?

Glue gun glue is safe for aquariums, but it won’t create a very powerful or durable bond. It’s likely to release within a few hours or days once underwater.

Will Super Glue Kill Fish?

Superglue doesn’t leach chemicals into your water, so it’s safe for fish. However, you need to make sure it dries before fish interact with it, as it can cause problems if they eat uncured super glue.

Is Gorilla Glue Safe for Aquariums?

Yes, Gorilla Glue is safe for aquariums once it has cured.

Is Gorilla Glue Safe for Saltwater Aquariums?

Some Gorilla Glue is safe for saltwater aquariums. Just make sure it’s a 100% cyanoacrylate super glue before using it in your tank.

Is Liquid Nails Aquarium-Safe?

Liquid Nails makes many products, some of which are perfectly safe. If you’re using Liquid Nails, make sure it’s a 100% silicone or 100% cyanoacrylate super glue formula.

Is Hot Glue Safe for Aquariums?

Hot glue (yes, the gun with the hot glue sticks) is safe for your fish as long as they don’t eat it. However, it doesn’t form a strong enough bond to last underwater, so it isn’t recommended for aquariums So while your fish won’t find hot glue toxic, it won’t be very useful to you as the fishkeeper.

What is the Best Aquarium-Safe Glue for Rocks?

A 100% silicone will often be the best glue for rocks. It’s thick and can fill in gaps to create the strongest bond. We recommend the SILA-SEAL Clear.

What is the Best Aquarium-Safe Glue for Plants?

A cyanoacrylate super glue gel is best for a planted tank (like anchoring Anubias to a hardscape) because it creates a secure bond quickly and will resist water movement. We recommend the Seachem Reef Glue.

What is the Best Aquarium-Safe Glue for Glass?

Silicone forms the best seal with glass, which is why it’s used to construct aquariums. We recommend the SILA-SEAL Clear for attaching decorations to the glass surfaces in your tank.

Aquarium safe glue used in beautiful fish tank

What is the Best Aquarium-Safe Glue for Me?

Aquarium safe glue is an important piece of your aquarium toolkit, just like aquarium-safe paints and aquarium-safe silicone. The best aquarium-safe adhesive for your tank will depend on what you’re looking to glue. Rocks and driftwood are best attached with 100% silicone, while a CA glue gel is best for most other small applications.

Our number one recommendation for its ease of use, rapid curing, and clean look once cured is the Seachem Reef Glue. It’s ideal for most fish tank gluing jobs and will make decorating more straightforward.

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