The Paludarium: When an Aquarium and Terrarium Fall in Love

Always wanted to bring nature into your home but can’t seem to keep a cactus from dying? The best way to avoid under (or over) watering your houseplants is to not have any … or better yet, plant them where they have access to their OWN water source, in a paludarium! Wikipedia defines a paludarium, or palo for short, as “a type of vivarium that incorporates both terrestrial and aquatic elements”. I prefer my far more florid description involving the romance between an aquarium and a terrarium that together form a world much like our own, consisting of both water and land. Regardless of how one describes a paludarium, almost anyone can use them to grow just about anything from those infamously tough orchids to high humidity bonsai trees and even house the entire life cycle of an amphibian all in a single tank!

Palos are living canvases that you paint with plants and running water, minus the threat of falling into the river or starting a territory dispute with neighborhood beaver gangs. When I was a child hiking in the woods I was always drawn to the sound of running water. I would chase the echo of splashing rivers and babbling brooks until I found the source where I insisted on either: setting loose any debris that had gathered, or in the cases where there were no obstructions, I would build my own dam to redirect flow to the other reaches of the stream-bed, temporarily altering a small ecosystem.

When I build my paludariums I start with large pieces of wood, rock, and cork as supportive scaffolding held and bonded in place with aquarium grade silicone and Great Stuff Pond & Stone expanding foam. Once I have the large stilted pieces of wood in place I begin to build the tank background and the land-feature or terrarium aspect of the palo. There are only so many ways a large branching piece of wood can fit in a tank, so instead of trying to assemble a mock representation or sketch out your intended design, I recommend simply starting with the largest piece and flip it around and place it in the tank to see how you like it and then build on top of it. It is often the case that I will use 45 minuets plus to arrange four chunks of wood then stand back and decide to go a different direction and pull everything out. The best advice I can give for this stage of the process is to take your time and think of it as a three dimensional puzzle where the wood and rocks interlock in natural ways to develop a serene looking scene to match your taste.

Once everything is in order and can support most of the structure I reinforce everything with the silicone where it has contact with the glass then pond foam to fill gaps and connect the individual pieces or cork, wood, and rock. Note that the pond foam does expand tremendously but after curing it will shrink just a bit and inevitably pull away from the smooth glass. When using the pond foam it is highly recommended that you wear gloves, I have ruined many shirts and embarrassed my partner in public with my black-blotched hands. When I use pond foam I quickly sprinkle shredded coconut husk, wood chips, or sand onto the foam while it is still wet and gently press on it to hide the shiny silver and give it a more natural texture that not only looks great but also gives the flora and fauna something to cling to and hide in. Chunks of cork bark sometimes have wonderful knotholes that are prefect for frog caves or makeshift planters and can be blended seamlessly into the background with the pond foam and coconut husk technique.

Depending on the style of palo you are building you can use a standard submersible pump around 180g/ph-300g/ph and a ridged “stand” pipe with a 90-degree elbow at the top or vinyl tubing to pump the water into a small cup to top-over and spill out of or more simply dump directly out onto the hardscape to race over the rock and wood. When building the water fall and installing the pump, I have found that if you cut a one inch (or wider) pipe to length and affix it behind the waterfall to run cords and tubing for the pump through, it makes the equipment more accessible for maintenance and repair/replacement. The pipe acts as a sleeve and keeps the foam or silicone from entombing the cords where they will then likely nary see the light of day. It’s a dreadful experience when you are forced to tear apart the dream stream you just finished creating all to replace a ten-dollar pump that died when it sucked in some sand. After the pump is in place the hardware, pipe and other non-natural aspects of the waterfall can be covered with cork, wood, rocks, even live (or fake, I suppose) plants to disguise the components and maintain the magical illusion of a natural stream.

Building the waterfall can feel daunting; although, once you have the big pieces in place and decide what look and sound you are going for it often begins to fall in place. There are many ways to redirect the flow in your palo to create a quietly glistening-trickle of water that effortlessly babbles into the pool below, or rushing torrents of white water that clamor over wood and rock to plunge into the turbulent reservoir. Note: due to waters surface tension, the aquascaper can use plant placement to help “pull” water in different directions to achieve desired effects. I use many different types of aquatic mosses and liverworts to coax the water where I want it to flow and will sometimes shove hardwood twigs into the waterfall to divert a steady drip onto a plant or into a collection pool.

Being a fanatical plant enthusiast, I was drawn to the opportunity to grow a wide plethora of plants inside my house year-round that benefit from having their feet wet or simply dipping their toes in the water-feature. There are many species of flowers that flourish in the microcosms developed in the stratified zones throughout your very own forest moon of Endor. There are gorgeous options for every inch of the paludarium, from the high and dry canopy of the cage to the wet and wild splash zone at the base of the waterfall.

Finding plants that grow best in your palo starts with some trial and error, try not to get too discouraged. If a few things don’t survive, remember that the tank is a living system trying to find its own equilibrium and some times the plant gods require a sacrifice. Anubias plants for example are common in planted aquariums but they can also happily grow out-of-water. They necessitate having most of their roots submerged in order to pull enough water through the plant to stand up and remain turgid. Just like in a planted tank, it's important not to cover the rhizome with substrate or moss but keep it submerged or damp while still allowing it to breathe. An aggressive growing anubias will creep across wood or rock and send out long vine like roots that trace the hardscape like a lightning bolt all the way down the tank in search of a drink.

Tillandsias, or air plants, on the other hand bloom magnificently towards the top of your micro jungle far from the water surface where the only moisture they receive is from the ambient humidity in the enclosure, a fogger, or from the occasional misting. It’s best for these plants to not have any permanent or direct contact with water or it will rot the leaves and likely kill the plant. Instead place these epiphytes on cork bark or in branches where air can freely circulate around them to help stave off mold and supply them with precious water.

Now that some plants are in place and the tank is laid out the way you like, its time to consider the inhabitants of this newly created world. Saltwater reef tanks benefit from having what’s commonly referred to as a “clean up crew” that is comprised of snails, crabs, and shrimps who scan the tank for any uneaten food or necrotic tissue which they quickly gobble up. The forest floor and your paludarium also provide home for insects that eat mold or mildew and help to keep the forest floor clean. Springtails are a common favorite among terrarium and paludarium builders because of their strong work ethic, by which I mean appetite, and their prolific nature. Springtails also make a great supplemental food source for young frogs and lizards, but they are predominantly set free with the intent of rummaging through the roughage and eating any mold that grows in these highly humid environments. Another cleaning critter that can help around the palo are isopods which come in an array of colors from orange to purple and spend much of their time in the soil recycling waste and rotting vegetation into consumable nutrients for plants. These little “rollie-pollies” are relatives of the wood lice one often finds in their woodpile. Unlike the springtails, isopods sometimes will need to have their numbers replenished, as they are not as rambunctious of breeders as the springtails but are equally as likely to be munched on by certain inhabitants.

Finally it is time to introduce the species chosen for the spectacular ‘scape you’ve sculpted! The internet is full of dissenting opinions on what can safely cohabitate with whom and how specific creatures should be housed, so I want to start by saying these are simply my opinions and observations I have gather through years of work with these little buggers and what works for me may not work for everyone. I have been enjoying my dart frogs living in palos with water features as shallow as an inch to as deep as a foot and have never lost a frog to drowning. Sure they miscalculate a jump and plunk right in the water but they immediately swim frantically to a branch, land, or some times the glass where they effortlessly climb out and attempt their stunt once more.