General Philosophy
Hardscaping
Substrate
Plants
Lights
There are as many ways to design a vivarium as there are reasons to do it. When I see a nice looking vivarium I like to try to get inside the head of the designer to try to understand what he or she was striving for in their design. With that in mind I thought I would describe my own philosophy and objectives as well as some of the general principles and elements I incorporate in an attempt to achieve them. Bear in mind this is my philosophy for designing my personal vivaria and don't be offended if my design principles are counter to your own. I have seen some incredibly beautiful and successful vivaria that do not meet my criteria at all and I wouldn't want to give the impression I am trying to tell people how things should be done.
At the most basic level I strive to create an environment that is a reasonable facsimile of the wild habitat where the species of frogs that I keep are found. Generally this means a bare substrate and leaf litter floor, a few aroids, exposed roots and many epiphytes. Although moss carpeted vivaria are beautiful they don't represent the typical natural environment of dart frogs so I don't do them. Instead I restrict moss patches to epiphyte logs and brightly lit water edges. I have not gone as far as biotoping (restricting plant and animal selections to only those found in a particular location in the wild) although I have been planning a large Costa Rican biotope for some time. However, when selecting plants I tend to select neotropical species as much as possible although the odd Asian or Australian plant has found its way into my vivaria. I do avoid plants that are icons of non-neotropical regions like the magnificently Asian Nepenthes. Likewise I avoid hybrids, preferring species instead. Very rarely I will choose a hybrid but generally I find the so-called "improvements" from hybridization to be an abomination of evolutionary perfection. So I don't like hybrids. I guess that's just something I'll have to work on with my therapist. Using these somewhat flexible restrictions I attempt to assemble a community the frogs will be comfortable and maybe even familiar with. In addition I try to design beyond the individual vivarium. I consider each vivarium as a single component of a the larger display of all of the vivaria in a room. To this end I use similar design elements inside the vivarium so that when viewed as a whole they appear to be pieces of a larger ecosystem. Outside the vivarium I make sure that cabinets, pedestals, light hoods, etc. are all built from the same species of wood with matching trim details so that all vivaria blend to form a coordinated collection. One of the best examples of a coordinated collection I've ever seen is the aviary at the St. Louis Zoo where identically designed cage units are tied together into a seamless display with a continuous planting of vegetation outside the units. The impression when you enter the building is that you have entered a large boundary-free universe of birds that blends fluidly from one ecosystem display to the next. My hope is that my modest collection of vivaria can exhibit a scaled down portion of that impact.
My design process begins with the hardscaping. Typically I develop a general idea of what I want and then I set out on a search for the required elements. Sometimes I reverse this and just search for some interesting pieces of wood and let what I find dictate my design. Luckily I live near the shore of a large reservoir so I can take a walk or canoe with chainsaw and tape measure in tow and choose from a large selection of potential hardscape items in the form of driftwood. Whenever possible I choose Osage orange or cedar for their decay resistance. Oak also works well but local soft hardwoods like cottonwood do not last long in my tropical vivaria. When I find what I'm looking for, I chainsaw the piece in to a manageable size but leave it oversized. Final shaping and sizing is done with a chainsaw but with the vivarium case nearby so I can frequently check the fit as the sculpting progresses. When placing hardscape elements I let my experience as an ecologist guide me. I try to envision a plausible ecological process that would result in a similar arrangement in nature. For example sedimentary rock always forms by compression of mineral sediments. Therefore sedimentary rock is formed, and usually found, in flat level layers. Additionally, the rocks have a top, bottom, and edges. Sedimentary rocks typically become exposed either by erosion from above that exposes their tops (i.e. a rocky stream bed), or from the side like when soil erodes from a hillside exposing the rock ledges. Following these guidelines from nature, I tend to place sedimentary rocks like limestone in level layers and exposing the tops, an edge, or some combination but always with the and at least one edge buried in substrate. Of course seismic activity can thrust rock layers up at an angle and this process could also be used in a vivarium. However, even in this case in nature, most of the rocks would still follow the similar angles and not just be jutting out of the ground at random angles. Weathering takes its toll on rocks too and natural rock layers almost always have many small bits and flakes that have weathered from the larger stones so I like to include small rock flakes to add a little extra detail. This basic idea is applied to every element placed in the vivarium. I ask whether I would see this in nature and, if so, how would it get there.
It may seem like this should be the first step in the process but it isn't for me. At least some hardscape elements always go in first with substrate filled around or over them to create natural looking layering and the perception that the elements have been anchored in the earth for a long time. My philosophy on vivarium substrates is well outside of mainstream thinking and somewhat controversial. Traditionally vivarium substrates have followed good greenhouse and nursery practices by providing loose, nutrient rich substrates to promote vigorous plant growth. I firmly believe that this is the wrong approach for vivaria. Given adequate light, it is all too easy to get vigorous growth inside a vivarium. Plants often literally push the tops off of vivaria. While frequent pruning can keep the problem in check, it is disruptive to the vivarium and its inhabitants and also requires time spent working that could be used enjoying the vivarium. I believe a better approach is to take another cue from nature and keep the plants hungry. Keeping the nutrient levels low not only slows plant growth to a tolerable pace but it also keeps plants and microbes competing for nitrogen which insures that nitrogenous waste produced by the animals does not build to toxic levels. Tropical rainforest soils are notoriously poor. Typically they are nutrient poor, low in organic matter, heavy clay soils that are so hard that roots have difficulty penetrating. These soils are poor because eons of rainfall have leached many of the minerals away and competition for nutrients by plants and microbes is so fierce that nutrients never have a chance to enter the soil and form a humus layer. Instead of deep organic soils rainforest soils are covered by a dense network of roots at the surface of the soil that quickly grab any nutrients released by decomposition of the leaf litter over them. In an attempt to simulate some of these characteristics I use pure clay kitty litter in most of my vivaria. The kitty litter forms a compact glop that is pretty inhospitable to most plant roots. It does a good job of forcing roots to grow on the surface which is nice aesthetically and does slow plant growth considerably. Obviously not many plants can grow in pure clay so I grow most of the plants epiphytically or I create perched planting pockets with sphagnum moss or some other low nutrient, high drainage material. Not all of my vivaria use kitty litter. I also have vivaria that use gravel or a mixture of fir bark, long fibered sphagnum, and compost as a substrate. All of these substrates have the common feature of being nutrient poor and I never fertilize. Of course no tropical forest substrate is complete without leaf litter. Biologically, oak leaves collected from my back yard work as well as anything but they don't look very tropical with their deep lobes or serrated edges. Instead I have been using magnolia leaves combined with leaves dropped by numerous house plants. Ficus benjamanii leaves make particularly nice looking litter. I recently planted a special garden with trees and shrubs that produce glossy simple tropical looking leaves specifically for use in vivaria.
I get my plants from a variety of sources but the bulk of them come from suppliers specializing in vivarium plants. These suppliers offer an interesting variety of plants that have proven to do well under vivarium conditions. When arranging plants in a vivarium I follow the same ecological rules I use for hardscaping. At the same time I ignore all of the rules borrowed from traditional gardening or terrarium books that tell you to plant in drifts and place the tallest plants in the back and short ones in front. These rules are fine for making plant displays but I've never seen a natural ecosystem that follows them. I like to create variously sized patches and pockets that are ideal for plant growth and then plant these with a variety of species without regard to whether a tall plant is hiding a shorter one. This is similar to the way plants grow in nature where a rock crevice that traps organic matter nurtures plant growth or a fallen log creates a nutrient rich bed of humus creates ideal conditions for a number of plant species. The kitty litter substrate helps in this regard because many plants don't do well in it so plants tend to stay in their pockets. If everything works right, the result is a patchwork of texture and color where patches of plants form a mosaic with patches of bare wood, rock, or soil. Having short plants partially obscured by taller plants tends to draw the viewer's eye deeper in to the vivarium to probe for other hidden secrets rather than lay it all out front like a table setting. To create the plant patches I play the same natural processes game and look for, or create situations that would accumulate organic matter in nature. Favorites are crevices between rocks and behind the uphill side of an exposed tree root. Another good choice is exposed hollows of logs. I fill each of these niches with a mixture of fir bark, long fibered sphagnum, and compost to create a moist, well drained area for plants to grow in. Either terrestrial or epiphytic species are planted in the pockets depending on the location and appearance. In addition to natural pockets of soil accumulation I also create epiphytic communities. In nature epiphytic communities usually form after moss has been able to grow sufficiently to create a moisture retaining seed bed for other epiphytes like orchids, bromeliads, ferns, aroids and others. Since tropical trees do not particularly like having epiphytes blocking light to their leaves, they have counter measures to make it difficult for epiphytes. Because of this, epiphytic communities can't grow just anywhere on a tree. Large horizontal limbs or smaller protuberances that trap moisture and organic matter are the perfect places for moss to get a start and create conditions for an epiphytic community. I look for similar places in the hardscape to back sphagnum moss to retain some moisture and plant a variety of epiphytes in it. For the finishing touch the sphagnum mat is covered with living moss. I always feel like I did a good job creating an epiphytic community if ferns and other plants sprout up from seeds or spores.
Proper lighting is the life blood of the vivarium and not only determines what plants can be grown but also affects the aesthetic appeal of the vivarium. The two main concerns are quality and quantity. Of the two I would have to say that quality is most important. By quality, I am mainly referring to the color temperature of the light. Even if you have low light intensity, you can find plants that will grow well under it but the color temperature of the lighting will make a big difference in how nice the vivarium looks. Anything in the 5000K to 6500K range is good but I personally prefer lighting in the 5000K to 5500K range. However, it's hard for me to imagine having too much light in a vivarium. That's why I use compact fluorescent lights in all my vivaria. Most of my lights are kits from AH Supply but I also use homemade 13w units in vivaria without enough room for larger bulbs or as filler light in larger vivaria. Some people claim that bright light is not a good idea with dart frogs. I think those claims are by people who have never tried compact fluorescent lights. Providing more light intensity provides many benefits. The range of plants that can be grown dramatically increases. The ability of plants to tolerate over watering increases. The growth of the plants becomes more compact and robust. And the colors of the foliage become more intense. The more compact growth of the plants leads to increased shading so frogs can actually get out of the bright light easier with high light intensity than without. The only disadvantage to using compact fluorescent lights is the heat they produce which is not terrible but can be a bit of a problem if you want to grow cool to intermediate temperature plants or frogs in a small vivarium. In this case getting the right balance of temperature and humidity requires a little work but is possible.