I still have a scar on my right palm from what my wife lovingly refers to as “The Great Dragon Stone Disaster of 2018.” Picture this: a meticulously arranged rock formation, standing proud in my 75-gallon tank for exactly three glorious days before catastrophically collapsing during a routine water change. The crash sent shards of stone into my hand, terrified my pearl gouramis into hiding for a week, and reduced me to the kind of colorful language that would make even the saltiest reef keeper blush.
That incident taught me an expensive lesson about gravity, water physics, and the absolute necessity of properly securing hardscape materials. I’ve since become something of an evangelist for proper rock-bonding techniques—partly because I never want another aquascaper to experience that particular brand of heartbreak, and partly because my wife has forbidden me from setting up another tank unless I “promise to glue the damn rocks together properly this time.”
Here’s the thing about rocks in aquariums that they don’t tell you in the glossy aquascaping magazines: water changes everything. Literally. That perfectly balanced stone arch that stands so confidently on your workbench becomes a potential disaster once submerged. Water reduces the effective weight of rocks by about 30%, which means your carefully balanced structures become significantly less stable underwater. Add in the occasional bump during maintenance, curious bottom-dwelling fish, or the subtle shifting that happens during water changes, and you’ve got a recipe for crushed plants, damaged glass, or worse.
After my disaster (and several other minor rock slides that I don’t admit to publicly), I’ve spent years testing different methods for creating secure hardscape structures. Some worked brilliantly; others failed spectacularly. I’m sharing what I’ve learned so you can avoid my mistakes—and the emergency room visits they occasionally entailed.
First, let’s talk about what NOT to use. Regular superglue (the liquid kind) is virtually useless underwater. It sets too quickly to get proper positioning and creates brittle bonds that fail under stress. Silicone sealant intended for aquarium construction works, but it takes forever to cure, requires completely dry surfaces, and creates obvious, unsightly seams. Epoxy putty sticks are okay in a pinch, but they’re usually glaringly obvious unless covered with plants or substrate. And please, for the love of all things aquatic, don’t use hot glue guns. Just… don’t. Trust me on this one.
After much trial and error (and one particularly memorable failure involving four pounds of seiryu stone and a brand-new custom tank bottom), I’ve settled on three reliable methods, each suited to different situations:
For most rock-to-rock connections, cyanoacrylate gel superglue is my go-to solution. Unlike the liquid version, the gel consistency gives you working time to position pieces correctly before it sets. The key is using the GEL formula—brands like Gorilla Gel, Loctite Gel Control, or any aquarium-specific cyanoacrylate gel work great. The gel stays where you put it instead of running everywhere and creating a mess.
This stuff works best when you’re constructing hardscape outside the tank. Rough up both surfaces lightly with sandpaper, clean them thoroughly, and let them dry completely. Apply the gel generously to one surface, press the pieces together firmly, and hold for 30-60 seconds. The initial bond happens quickly, but—and this is crucial—let it cure fully for at least 24 hours before submerging. I learned this the hard way when I rushed a build and watched in horror as my “securely bonded” rocks separated like a slow-motion divorce about twenty minutes after filling the tank.
The gel method works brilliantly for creating complex structures before they go into the water. I pre-build nearly all my hardscapes on a dedicated workbench now, letting them cure fully before they go anywhere near water. But what about adjustments once your tank is filled? That’s where the second method comes in.
For underwater connections or adding pieces to an established tank, nothing beats the combination of cyanoacrylate gel and fine-grained substrate. This trick changed my aquascaping life. Apply a generous dollop of gel superglue to one rock surface, then immediately press the rocks together underwater. Here’s the magic part: while still holding the rocks together, sprinkle a generous amount of fine sand or aquasoil directly onto the joint. The substrate particles accelerate the curing process and physically reinforce the bond—plus, they camouflage the glue joint perfectly.
I wish I could claim I invented this technique, but I learned it from a reef keeper who used it with coral fragments. It works just as well for freshwater hardscaping, creating bonds that are both strong and nearly invisible. I’ve used this method to attach small accent stones to larger structures, secure plants to rocks, and even make emergency repairs without draining the tank.
For heavyweight constructions or particularly precarious stacks, I bring out the big guns: epoxy putty formulated specifically for aquarium use. Products like Milliput, Pondstone, or TwoLittleFishies Stoneworks are my favorites. These two-part epoxies come as separate components that you knead together to activate. Once mixed, you typically have 15-30 minutes of working time before they begin to harden.
The technique here is different. Instead of trying to create invisible joints, I use the epoxy to create “mortar” between rocks—much like building a miniature stone wall. The key is to embrace the method and make it part of your design. I’ve created incredible terraced landscapes using dark gray epoxy as visible mortar between lighter stones, mimicking the natural sedimentary rock formations I’ve seen while hiking in Arizona. With careful color matching and a bit of artistic texturing (toothpicks are great for this), epoxy mortar can actually enhance your hardscape rather than detract from it.
The beauty of the epoxy method is the strength it provides. I’ve created cantilever extensions and arches that would be impossible with glue alone. The downside is that most require 24-48 hours to cure fully before submersion, and some varieties release ammonia during curing—meaning you’ll need to do extra water changes at the beginning.
Whatever method you choose, always plan your hardscape with long-term stability in mind. The “rule of three” has saved me countless headaches: every rock should have at least three points of contact with other surfaces. This triangulation principle creates inherently stable structures, whether or not they’re glued. I also generally avoid tall, narrow towers unless they’re extremely well-secured to a broad base. Physics always wins eventually.
Remember too that plants can help reinforce your structures over time. Strategic placement of rhizome plants like Anubias and Bucephalandra can help bind rocks together naturally as they grow, while the dense root systems of stem plants and carpeting species can stabilize substrate around your hardscape base.
The dragon stone structure that once collapsed on me has been rebuilt in my current display tank—this time properly secured with a combination of all three methods. The formation has weathered countless water changes, survived a cross-country move, and even endured my overly enthusiastic nephew tapping on the glass repeatedly during holiday visits. The gouramis swim peacefully through the arches, and I sleep soundly knowing I won’t wake to the sound of catastrophic hardscape failure.
My palm scar has faded to a thin white line, but the lesson remains crystal clear: in aquascaping, as in life, sometimes you need the right connections to stay upright when the currents get strong. Take the time to secure your hardscape properly, and your underwater landscape will stand the test of time—and water changes—for years to come.
