Updated August 2026
The best reef epoxy and glue depends on the job; there is no single adhesive that replaces every other option. For mounting coral frags, my first choice is BRS Extra Thick Gel Super Glue. For the epoxy layer in my glue–epoxy–glue sandwich, I use Tunze Coral Gum Instant. I still use every product in this guide; each one solves a different problem.
My super-glue pick
BRS Extra Thick Gel Super Glue
This is my go-to glue for mounting coral frags. The thick gel stays where I place it, fills small gaps, and forms the sticky outer layers of the method I use on my own aquascapes.
Best for: Reef keepers who mount frags regularly and want the value of a large bottle.
My epoxy pick
Tunze Coral Gum Instant
Coral Gum is the epoxy I reach for when mounting frags or lightly stabilizing an aquascape. It mixes without the strong odor of many putties and cures with a slightly rubbery, workable feel.
Best for: The structured middle layer beneath a coral frag or a light-duty rock connection.
The adhesive system I actually use
This glue–epoxy–glue sandwich is the method I trust for mounting frags directly onto an aquascape. Super glue provides the tack; epoxy fills the gap and supplies structure. Together they work better than either material usually does alone.
Compare my reef epoxy and glue recommendations
These products are complementary rather than interchangeable. Choose the material by the job: mounting a frag, building dry rockwork, hiding a seam, accelerating an exposed glue joint, or supporting a heavier structure.
| Product | Material | Best use | My experience |
|---|---|---|---|
| BRS Extra Thick Gel, 10 oz | Thick cyanoacrylate gel | Frequent frag mounting | My everyday super glue |
| BRS General Bonding Glue | Thin cyanoacrylate | Cotton joints, tight seams, and rock dust | A specialized aquascaping tool I still use |
| BRS Extra Thick Gel, 20 g tube | Thick cyanoacrylate gel | Occasional use and underwater application | Easier to manage than a large bottle |
| Insta-Set Accelerator | Super-glue accelerator | Creating a fast outer shell on exposed glue | Useful during dry aquascaping |
| Tunze Coral Gum Instant | Two-part epoxy | Frag mounting and light structure | My go-to reef epoxy |
| Two Little Fishies AquaStik | Two-part epoxy putty | Heavier, more cement-like support | Strong but smelly and skimmer-reactive |
How I chose these reef adhesives
I have personally used every glue, accelerator, and epoxy in this guide, and I still use all of them. I chose them by matching each product to the job it performs best—not by pretending that a thin glue, a thick gel, an accelerator, and two different epoxies are direct substitutes.
BRS Extra Thick Gel plus Tunze Coral Gum.
BRS General Bonding Glue with cotton or rock dust.
The smaller 20 g tube of Extra Thick Gel.
Two Little Fishies AquaStik when I want a harder, cement-like cure.
My six reef epoxy and glue recommendations
1. BRS Extra Thick Gel Super Glue — 10 oz Bottle
My experience: This is my absolute go-to glue for mounting coral frags, and I continue to use it on my own aquariums.
Frequent frag mounting and good bulk value
You use very little glue or need to dispense it underwater
The extra-thick consistency stays in place instead of running into the rock. It works especially well as both sticky layers around a small amount of epoxy.
The bottle itself should stay out of the aquarium. Its dispensing tip also tends to clog, so expect to trim or clear the tip between uses. The current bundle includes dispensing tips, but if you only mount an occasional frag, a smaller tube can be more manageable.
My verdict: The super glue I would buy first if you expect to mount frags regularly.
2. BRS General Bonding Super Glue
My experience: I use this thin, water-like glue for detailed dry aquascaping jobs—not as my normal coral-frag glue.
Cotton joints, narrow seams, and rock-dust camouflage
You need a gel that stays beneath a coral frag
For a dry aquascape joint, I can pull apart a small piece of cotton, place it between wood and rock or between two pieces of rock, and saturate the cotton with this thin glue. The cotton hardens into a surprisingly useful connection.
It is also excellent for hiding visible seams. Apply the glue over a cured joint and sprinkle matching rock dust into it. Once it hardens, the repair blends into the aquascape far better.
My verdict: A specialized but extremely handy glue for building and finishing a dry aquascape.
3. BRS Extra Thick Gel Super Glue — 20 g Tube
My experience: This is the same useful extra-thick style in a smaller format that is easier to manage and store.
Occasional frag mounting and underwater dispensing
Less economical if you mount many frags
The tube is a better choice when you do not use enough glue to justify the large bottle. It also does not draw air back into a rigid bottle in quite the same way after you squeeze it, which makes it more practical when you need to dispense glue underwater.
My verdict: Buy a few tubes instead of the 10-ounce bottle if you only mount frags occasionally or want a compact underwater option.
4. Insta-Set Super Glue Accelerator
My experience: I use accelerator when I am building dry aquascapes and do not want to hold a joint in place while the exposed glue begins to set.
Hardening the outside of an exposed glue joint quickly
The center of a thick glue mass still needs time to cure
A light spray creates a hardened outer shell around the super glue, which can stabilize the joint much faster. It does not magically cure the entire interior of a large blob, so the structure still needs to be handled carefully while the bond finishes curing.
My verdict: Not an adhesive by itself, but a worthwhile companion when you build a dry aquascape with super glue.
5. Tunze Coral Gum Instant
My experience: This is the reef epoxy I use most often for coral frags and light-duty aquascape support.
The structured center of a glue–epoxy–glue joint
Slightly rubbery rather than cement-hard
It is easy to mix in small amounts, stays workable long enough to shape, and does not have the harsh odor I associate with some other aquarium putties. I use it when I want structure without committing to a heavy cement-like repair.
My verdict: My first epoxy choice for mounting coral frags and making modest aquascape connections.
6. Two Little Fishies AquaStik — Coralline Red
My experience: I use AquaStik when I want a harder, more cement-like result for larger pieces of aquascape.
Heavier structural support and larger joints
Strong odor and a protein-skimmer reaction
AquaStik cures harder than Coral Gum, which can be useful when the joint needs more structure. The downside is the strong smell while mixing it, and it can make a protein skimmer overflow or produce excessive foam.
Plan to turn the protein skimmer off while the system reacts, then restart it carefully and watch the collection cup rather than assuming the skimmer will behave normally.
My verdict: The epoxy I choose when I care more about a hard structural cure than odor, convenience, or skimmer behavior.
Use the lightest adhesive system that safely does the job
A coral frag normally needs a small, stable connection—not a giant mass of glue or epoxy. Dry-fit the location first, use enough material to fill the irregular space, and avoid burying living coral tissue. For a large aquascape joint, build and test the structure outside the aquarium whenever possible.
Which reef epoxy or glue should you buy?
| Your job | My pick | Why | Watch for | Price |
|---|---|---|---|---|
| Mount coral frags regularly | BRS Extra Thick Gel, 10 oz | My go-to thick gel and best bulk value | Clogged dispensing tip | Check BRS price |
| Build or disguise dry-rock seams | BRS General Bonding Glue | Thin enough to saturate cotton and accept rock dust | Too runny for normal frag mounting | Check BRS price |
| Mount only a few frags | BRS Extra Thick Gel, 20 g tube | Compact, manageable, and underwater-friendly | Higher cost per amount of glue | Check BRS price |
| Stabilize exposed glue quickly | Insta-Set Accelerator | Forms a fast outer shell during dry work | Interior glue still needs cure time | Check BRS price |
| Add structure beneath a frag | Tunze Coral Gum | Odor-free, workable, and my epoxy pick | Not the hardest structural cure | Check BRS price |
| Support a heavier rock joint | Two Little Fishies AquaStik | Harder, cement-like cured structure | Odor and protein-skimmer overreaction | Check BRS price |
Reef epoxy and super glue FAQ
What is the best glue for mounting coral frags?
BRS Extra Thick Gel Super Glue is my first choice. I normally combine it with a small amount of Tunze Coral Gum in a glue–epoxy–glue sandwich so the gel supplies tack and the epoxy fills the uneven space.
Should I use reef epoxy or super glue?
For many frag-mounting jobs, use both. Super glue grips the surfaces, while epoxy fills gaps and provides structure. Thin bonding glue, thick gel, and hard epoxy putty each solve different problems.
Can super glue be used underwater?
Extra-thick cyanoacrylate gel can be used underwater, but I prefer a small tube for that job. I do not submerge the large 10-ounce bottle.
What is thin super glue useful for in an aquascape?
I use BRS General Bonding Glue to saturate small cotton joints and to hold matching rock dust over visible seams. Its water-like consistency is useful in tight gaps but too runny for my normal frag-mounting method.
Does super-glue accelerator cure the whole joint instantly?
No. It hardens the exposed outside of the glue quickly, which can stabilize the joint, but the interior of a thick glue mass still needs time to cure fully.
Why does reef epoxy make a protein skimmer overflow?
Some epoxy putties can temporarily change the water in a way that makes a protein skimmer produce excessive foam. AquaStik has done this in my experience, so I turn the skimmer off and restart it carefully after the aquarium settles.
Build the aquascape before you mount the coral
Use the Reef Rock Buying Guide to choose the shapes you are bonding, the Saltwater Tank Setup Guides to place and test the structure safely, and the Livestock Guides before choosing where a coral should live.
