7 Popular Aquarium Adhesives, Which One Is The Strongest?

Getting the right adhesive can really "make or break" your aquascape. Ok so pun intended here because we set up three experiments to test seven popular adhesives used to build aquascapes and attach rocks together in a saltwater aquarium.  We hope to broaden our understanding of coral and rock adhesives and formulate fact-based answers to these questions.

1 -Which adhesive creates the strongest bond?

2 - Does it matter if the rocks are dry/wet when adhering them together?

3 - When is epoxy a better choice than cyanoacrylate (super glue) gel? Does a combo work best? 

Adhesives We Tested

• Jurrasic Gel
• Jurrasic Gel with Insta-Set
• BRS Extra Thick Gel
• BRS Extra Thick Gel with Insta-Set
• E-Marco-400 Mortar
• Two Little Fishies Underwater Epoxy
• E-Marco-400 Mortar, BRS Extra Thick Gel, and Insta-Set combo as seen in our popular NSA Aquascape Video

Bond Strength Experiment #1 - Dry Rock

For this test, we simply cut up some Caribsea LifeRock Branch using a bandsaw then glued it back together. We purposeful created a flat cut when splitting the branches to eliminate any kind of mechanical interlocking advantage and minimize available surface area for adhesion.  After 24 hours of curing, each of the 7 branch pieces with different adhesives was put through a series of "stress tests" to see how much abuse they could take before separating.  

Two of these were clear winners, with Two Little Fishies Epoxy and the NSA Aquascape - Mortar/Glue combo creating the strongest bond between two pieces of dry rock. To quote Randy (who performed the stress tests himself) "The strongest bond award goes to the TLF epoxy".  

Bond Strength Experiment #2 - Wet Rock

We set up the second test using branch rock that was left to soak in salt water for 72 hours before gluing. We then proceeded to glue them together, again using the flat surface, and allowed them to cure underwater for 24 hours. The stress tests we performed were identical to experiment #1.

We were curious to see how a wet surface would affect the adhesives.  After all, it is not uncommon to build or repair an aquascape with wet live rock.

Again, two clear winners, but this time the BRS Extra Thick Super Glue gel held up the best. Very interesting to see the Cyanoacrylate (super glue) performed BETTER with a wet surface.

This also raises the question about the difference between Jurassic Gel and BRS Glue, after all, they are both cyanoacrylates. We suspect there are differences in the chemical composition and additives used in making the two super glue products; it is hard to be certain without a list of ingredients or chemical analysis.

Bond Strength Experiment #3 - Complete Aquascape

For our third and final adhesive showdown, we used the same adhesives to build a classic arch-shaped aquascape with Reef Saver Dry Rock. The arches are all made from the same number of rocks of similar size. We let them cure for 24 hours before performing different stress tests on each aquascape with the final test being a 5ft vertical free-fall onto the concrete floor. 

While we had a great time smashing up some aquascapes, only one victor pulled through 3 of the 4 stress tests. Nonother than Two Little Fishes Epoxy.

Its evident epoxy creates an impressive bond when left to cure for 24 hours out of the water and, against our previously misguided judgment, is the best choice for building strong aquascapes out of dry rock. Conversely, if your working with wet rock, BRS Extra Thick Super Glue Gel has proved to create the most reliable bond.