Aquarium Glue for Rocks

Securing rocks, corals, and other decorative elements in an aquarium can be challenging. Choosing the right aquarium-safe adhesive is crucial to create a natural-looking underwater landscape that is also safe for the fish and plants. This comprehensive guide covers everything you need to know about selecting, using and making aquarium glue for rocks.

An Overview of Adhesive Options for Aquascaping

When it comes to aquascaping, aquarium owners have several options for safely securing rocks, corals, and other decorative elements underwater. Here is an overview of the most common aquarium glue types:


Epoxy is a two-part adhesive that mixes an epoxy resin with a polyamine hardener. Combined, these two components undergo a chemical reaction and harden into an extremely strong, cement-like substance perfect for bonding rocks.

Epoxy is ideal for large aquascaping projects as it can adhere heavy rocks and build up a substantial rockscape structure. Once cured, epoxy forms a rigid bond completely waterproof and insoluble in water. This makes it one of the most durable and long-lasting aquarium glues available.

Most epoxies marketed for aquarium use are reef safe and do not contain any toxic ingredients that could leach into the water. Popular picks are Reef Spar Epoxy and SeaStar Rigid Aquarium-Safe Epoxy Putty.

Super Glue Gel

Super glue, also known as cyanoacrylate adhesive, comes in handy single-use tubes or larger gel bottles. It works well for adhering smaller rocks, corals, and frag plugs in an aquarium.

Choosing a thick gel-based product is important rather than a runny liquid glue when selecting a super glue. The gel consistency ensures the glue stays in place instead of dispersing through the water. It also allows applying a more generous amount to fill gaps and create a stronger bond.

Some well-known super glue gels for underwater use are API Aquarium Super Glue GelSeachem Reef Glue Cyanoacrylate Gel and Tunze Aquatics Coral Glue. Avoid generic super glues as they can contain potentially toxic ingredients.

Silicone Sealant

Silicone sealant or aquarium silicone is another popular adhesive for secures rocks in an aquarium. This flexible, rubbery product remains permanently pliable when cured, allowing some movement.

GE Silicone I Sealant and Momentive Aquarium Sealant are two trusted brands of 100% silicone that work well for aquarium applications. Avoid silicone sealants formulated with fungicides or mold inhibitors, as these can leach chemicals into the water.

Silicone sealant is easy to apply from a caulking gun and offers a decently strong, waterproof bond. However, it may not be the best choice for heavy rock structures.

Underwater Curing Adhesives

Some glues and epoxies are specifically designed to cure underwater. This allows directly gluing rocks or corals in the tank rather than drying them out.

Tunze Coral Glue is one example of such an adhesive. This fast-setting epoxy putty sticks well to wet surfaces and forms permanent bonds when submerged. Using an underwater curing product can speed up the aquascaping process.

All-Purpose and Specialty Glues

In addition to the major types above, some specialty aquarium glues serve specific adhesion needs:

  • Cyanoacrylate gel: Fast-bonding super glues like Tunze Coral Glue work well for gluing small coral frags or fragments.
  • Two-part epoxies: Used to cement rocks together or onto tank decorations firmly. Popular picks are Water Weld Epoxy Putty and Amazing GOOP Plumbing Epoxy Putty.
  • Plastic adhesives: For bonding plastic plants or decorations underwater. Amazing GOOP Plastic Bonding Cement is one example.
  • Driftwood adhesives: Special epoxies like Seachem Flourish Glue designed for securing wood in an aquarium.

How to Choose the Best Aquarium Glue

With so many adhesive options, deciding which is the right glue for your aquarium project can be tricky. Here are some tips for selecting the best aquarium glue for rocks or corals:

Consider Bond Strength

The strength of the bond is important – a weak glue can cause elements to detach and fall, potentially damaging corals. Epoxy and silicone provide the strongest adhesion for rocks while super glues work better for small corals.

Assess Safety

Select an aquarium-safe adhesive that won’t leach harmful chemicals into the water or affect aquatic life. Read product descriptions carefully and look for reef-safe designations. Cyanoacrylate gel and pure silicone are safe bets.

Factor in Drying Time

Faster drying glues like super glue gel allow securing rocks more quickly while epoxy may require clamping elements for several hours until fully cured. Consider project needs when deciding on drying time.

Mind the Texture

Thicker gel adhesives are better for filling in uneven surfaces and gaps. Epoxy putties also mold well to textures. Liquid glues seep away from the bonding area.

Consider Versatility

Some adhesives, like silicone sealant and plastic epoxy, have many uses around the aquarium. Opt for a versatile glue if you attach other items like plastic plants.

Evaluate Cost

While specialized aquarium adhesives can be pricier, some budget-friendly options like super glue gel also create strong bonds safely. Evaluate cost per use when purchasing.

Step-By-Step Guide to Gluing Rocks in an Aquarium

Once you’ve chosen the best glue for your needs, follow these steps for securely adhering rocks in a tank:

Clean Surfaces

Remove any debris, dust or oil from the surfaces to be glued. This helps the adhesive bond tightly to the rocks.

Apply the Glue

Follow product instructions for evenly applying the right amount of glue to both surfaces. Using too little glue can result in a weak bond.

Press Together

Immediately press the rocks firmly together in the desired position and hold for 30-60 seconds. This ensures maximum contact for the glue to adhere.

Clamp Larger Rocks

For heavier rocks or load-bearing structures, use plastic clamps or braces to hold the rocks tightly together as the glue sets.

Allow Proper Curing Time

Refer to product guidelines and wait the recommended time for the glue to fully cure before submerging underwater. This could range from 10 minutes to several hours.

Check Seals Before Flooding

Inspect the bonds and seals around rocks to ensure they are completely set before carefully flooding the tank. Immediately remove any rocks that appear loose.

DIY Aquarium-Safe Rock Glue Recipes

For the DIY enthusiast, making your own aquarium glue for adhering rocks using common household items is possible. Here are a few recipe ideas to get you started:

Flour-Based Rock Glue

  • Ingredients: 2 tablespoons flour, 4 tablespoons water, 1 teaspoon salt
  • Directions: Mix ingredients into a thick, smooth paste. Apply to rocks, press together, and allow to dry completely before adding to tank. The dried flour paste will hold rocks firmly.

Gelatin Rock Glue

  • Ingredients: 1 packet unflavored gelatin, 2 tablespoons water
  • Directions: Soak gelatin in the water for 5 minutes. Microwave for 10 seconds until dissolved. Apply gel mixture to rocks and press firmly for 1 minute until bonded. Allow to set completely before submerging.

Clear Silicone Glue

  • Ingredients: Clear hobby glue or PVA glue, baking soda
  • Directions: Mix a few teaspoons of baking soda into the clear glue until it takes on a thicker, opaque silicone-like texture. Use immediately to glue rocks and let bonds cure fully before adding to the aquarium.

Cornstarch and Vinegar Glue

  • Ingredients: 1 part white vinegar, 2 parts cornstarch
  • Directions: Heat vinegar to a simmer then slowly whisk in cornstarch. Stir continuously until mixture thickens to a glue-like consistency. Allow to cool fully before using to adhere rocks. Cures into a hard bond.

Using Super Glue Gel in Aquarium Rockscapes

super glue gel is a popular choice for securing rocks when aquascaping due to its fast drying time and ability to bond well underwater. Here are some tips for using cyanoacrylate super glue effectively when building rock structures and decorations in your aquarium:

Select the Proper Super Glue Gel Product

As mentioned, choosing a cyanoacrylate formula specifically designed for aquarium use is crucial rather than a standard super glue. Reef-safe super glue gels, like API Aquarium Super Glue Gel, are ideal choices for water applications.

Prepare the Rock Surfaces

Ensure all rock surfaces are clean, dry, and debris-free so the super glue bonds tightly. For underwater gluing, the rocks can be damp but shouldn’t be dripping wet.

Apply a Generous Amount of Gel

Don’t skimp on the super glue – a generous amount helps create a complete seal and fills in crevices between rocks.

Hold Rocks Firmly Together

Press rocks into the intended position and hold together very firmly for at least 60 seconds to allow the glue to set properly. The tight contact helps maximize bonding power.

Work in Sections for Large Projects

When creating a heavy or extensive rockscape, glue rocks together in small sections then allow them to cure before adding more. This prevents supportive glued sections from shifting.

Let Glue Cure Fully Before Flooding

It takes cyanoacrylate glue at least 12 hours to harden and cure underwater fully. Wait overnight before carefully filling the tank to avoid disrupting unfinished bonds.

Check for Secure Bonds

Inspect the glued rocks for weak points and remove and re-glue any loose sections. Super glue sets fast but flooding too soon can undermine the curing.

With proper application, super glue gel creates strong, long-lasting bonds underwater to adhere to aquarium rock decor and landscapes securely. Just be sure to use an aquarium-safe formula and let it cure completely.

Frequently Asked Questions

What types of glue can be used safely in aquariums?

When used properly, silicone sealant, cyanoacrylate gel super glues, and epoxy putties designed for underwater use are generally considered safe for aquariums. Avoid household glues.

How do I glue large aquarium rocks together?

Start by cleaning the rock surfaces. Apply epoxy putty or plumber’s putty and press the rocks together firmly for several minutes until well adhered. Use plastic braces to hold heavy rocks in place until the epoxy fully cures.

Can I use super glue to attach corals to rocks?

Cyanoacrylate super glue gels are recommended for attaching small coral fragments or newly propagated corals to rocks or plugs. Just be sure to use an aquarium-safe formula and apply a generous amount.

What is the best glue for gluing plastic aquarium plants and decor?

Silicone sealant and plastic bonding epoxies like Amazing GOOP work well for gluing plastic items. Super glue can also bind plastic but may create a brittle bond more likely to break.

How long does it take most aquarium glues to cure?

Curing times range considerably based on products used. Silicone and super glues set within an hour while epoxies require several hours up to 24 hours to fully cure. Always check manufacturer guidelines.

Can I use hot glue in a fish tank?

No, standard hot glue contains toxic ingredients and does not work well for bonding underwater. Specialty hot glue formulated for plastics may be aquarium safe but other adhesives like silicone work better.

Is wood glue safe for attaching driftwood in an aquarium?

Wood glue is not recommended since it can leach chemicals as it breaks down underwater. Opt for an aquarium-safe silicone or epoxy putty designed for gluing driftwood and decor.

How can I remove a rock glued in place in my aquarium?

Removing securely bonded rocks can be difficult but can be done carefully with a plastic putty knife or razor to scrape away at the glue. Take care not to shatter rocks or scratch glass.

Is epoxy putty sticky and messy to work with?

Most epoxy putties feel dry and clay-like rather than sticky, and form a non-dripping ball that’s easy to handle. Plastic gloves help minimize mess when kneading and applying the putty.

Key Takeaways on Choosing Aquarium Glue

  • Epoxy putties provide the strongest bonding power for heavy rock structures while super glues work well for gluing small corals.
  • Always select adhesives designed specifically for aquarium use like silicone sealant, cyanoacrylate gel, and epoxy putty for coral and rock gluing.
  • Let all bonds cure fully before submerging underwater. Super glue takes at least 12 hours to cure completely when used underwater.
  • For large projects, glue rocks in sections and use plastic braces to hold together while curing rather than attempting to glue all at once.
  • DIY glue recipes can be used but should be tested thoroughly and allowed to cure fully before adding homemade glues to a tank.

Using Silicone Sealant for Aquascaping Projects

Silicone sealant is a versatile aquarium glue used in various ways when designing rockscapes and decorations. Here are some tips for working with silicone to attach rocks and other elements:

Choosing the Right Silicone

  • Select a pure silicone sealant without any added fungicides or chemicals. Popular brands like Momentive Silicone and GE Silicone I are safe choices.
  • Opt for a clear formula to hide bonds unless you want to use colored silicone for accenting intentionally.
  • Ensure the silicone is formulated for aquariums rather than bath or sink applications.

Applying Silicone in Rockscapes

  • Use a caulking gun to control the amount of silicone applied. Don’t apply too much.
  • Lay down an even bead of silicone where the rocks meet rather than covering the entire surface.
  • Press firmly together for at least 30 seconds to smoosh the silicone into a thin bond layer.
  • Fill any gaps thoroughly but wipe away excess squeeze-out for a neat look.

Adding Texture with Silicone

  • You can use colored silicone to create “veins” on rocks for a natural look. Trail thin lines of silicone across surfaces.
  • Press sand, pebbles, gravel or other substrates into fresh silicone to coat rocks with different textures as the silicone dries.

Using Silicone for Other Aquarium Elements

  • Adhere plastic plants, tubing and decorations with strong silicone bonds.
  • Seal any small leaks or holes in the aquarium glass with waterproof silicone.
  • Attach moss, ferns or anemones to rocks, wood or decor with a silicone dab.
  • Create a silicone bed or mound to lay corals on rather than directly gluing corals.

Creating Naturalistic Rockscapes with Epoxy Putty

Epoxy putty is ideal for sculpting natural-looking rock formations, overhangs and caves to create an underwater habitat. Follow these tips when using epoxy putties like Water Weld for aquascaping:

Kneading and Handling Epoxy Putty

  • Start by kneading the two putty components together well until completely blended.
  • The putty will feel dry and clay-like rather than sticky when mixed thoroughly.
  • Pinch off sections as needed rather than mixing the whole amount at once so you don’t waste any.

Shaping and Bonding Rocks

  • Roll putty ropes like clay to fill gaps or holes in existing rocks. Smooth with wet fingers.
  • Press putty firmly around rocks to fuse them into interesting shapes. Allow time to bond before shaping further.
  • Use textured items like plastic nets to imprint natural patterns onto the putty.

Constructing New Rock Elements

  • Form entirely new rocks, overhangs and tunnels by shaping the putty over foam, containers or other forms.
  • Create layers, peaks and valleys by pressing separate putty sections together and sculpting.
  • Use putty to affix or embed shells, pebbles, crystals and other decorative additives.

Innovative New Aquarium Glue Products

While standard glues like silicone, epoxy, and super glue remain aquarium staples, some innovative new products also make waves in underwater bonding and repair.

CorAffix Zoa Coral Glue

This cyanoacrylate glue by CorAffix comes in an ultra-precise applicator tube for bonding aquacultured coral frags. The controllable fine tip minimizes mess and prevents damaging fragile zoanthids during fragging.

Kontakt-Chemie Aquarium Pro Epoxy

Two steel tubes house the resin and hardener, which mix directly out the nozzle for easy, mess-free epoxy application underwater. The fast-curing formula is designed specifically for aquariums.

Hydromend Underwater Repair Compound

Hydromend is an emergency repair product that stops leaks in glass or acrylic aquariums, allowing time for a proper fix. Knead the putty, roll it into a “snake, ” and press firmly over underwater cracks.

Fritz Aquatics FritzZyme Turbo Start 700

This blend of beneficial bacteria jumpstarts the aquarium nitrogen cycle, allowing instantly gluing and adding new rocks without worrying about subsequent ammonia spikes from uncured adhesives.

Continuity Check Gel for Pools and Aquariums

Check underwater glues, silicone, and acrylic seals for hidden flaws using this conductive gel. Just smear it on and use a continuity checker tool to detect cracks or thin spots in the bond or seal.

The Art of Aquascaping with Rocks and Driftwood

For creative aquarium owners, sculpting artistic underwater landscapes with rocks, wood, coral and plants is an engaging form of living art called aquascaping. Here are some tips for arranging and adhering elements to create a stunning aquascape:

Start with a Focal Point

Every good composition has a visual focal point – this could be an striking piece of driftwood, a prominent rock formation or dense plant grouping that draws the eye.

Follow Rule of Thirds

Divide the tank into thirds vertically and horizontally and place key elements along these lines or at intersections. This creates balance.

Layer Heights and Textures

Vary the heights of rock piles and integrate different textures like smooth river rocks, chunky stones, branches and leafy plants.

Use Odd Numbers

Odd-numbered rock groupings and plants look more organic. Place decorative elements in groups of 3, 5 or 7 rather than symmetrical pairs.

Contrast Colors

Contrast cool blues and greens of water plants with warm red hues of driftwood or terracotta structures for visual interest.

Glue Elements Securely

Use aquarium-safe silicone, epoxy or superglues to adhere heavy decorative elements in position and prevent dislodging firmly.

Troubleshooting Common Aquarium Rock Glue Problems

Gluing rocks in aquariums seems straightforward but can encounter frustrations. Here are some common problems and solutions:

Problem: Rocks won’t stay in place when positioning.

Solution: Use dabs of putty or silicone to “tac” rocks in place temporarily for positioning before permanently gluing.

Problem: Glued rocks shift or detach after flooding tank.

Solution: Ensure adhesive cured fully before flooding. Re-glue any loose sections and use braces until the bond sets completely.

Problem: White hazy bloom or residue on rocks from glue.

Solution: Remove residue with a plastic scrub pad and siphon it out. Ensure future glue bonds cure fully before flooding.

Problem: Epoxy putty won’t mix properly or harden.

Solution: Knead the putty vigorously until it achieves an even color with no light or dark streaks, indicating proper mixing.

Problem: Super glue creates web-like white strands in water.

Solution: Remove all residue with an algae scraper and large water change. Apply very small amounts of glue in future.

Problem: Silicone sealant won’t set.

Solution: Ensure sealant is fresh and hasn’t expired. Acetic acid from old product prevents curing.

Final Thoughts

Aquarium-safe adhesives allow for the secure attachment of rocks, corals, and decorations, creating a beautiful underwater environment. Specialty products like cyanoacrylate gel, silicone sealant, and epoxy putty allow long-term underwater bonds, easier coral fragging, and emergency leak repair. Proper adhesion and bond cure before flooding prevent frustrations like detached rocks. With practice, anyone can create stunning rock formations, coral landscapes, and driftwood accents that keep fish and invertebrates healthy and happy.