Common Terrarium Mistakes: From Wilted Plants to Bleach Dips
Here is a collection of the most common questions/problems I’ve seen with people growing plants in terrariums, compiled from my years of vending reptile shows.
Wilted plants caused by damaged or rotted roots or too low humidity
Plants can wilt for a variety of reasons in a planted terrarium, surprisingly the most common reasons have nothing to do with the soil being too dry. Root damage from removing soil or treating a plant can cause the leaves to wilt, the plant no longer has the root system to support the leaves so they wilt and begin to drop off. Overwatering the soil and rotting the plant roots also has the same effect. Another reason can be too low of humidity. Instead of overwatering the soil, try covering more of the screen lid with either glass or saran wrap, or increase your misting (within reason). Too much misting can also overwater the soil, rotting the roots and causing the plant to wilt even further.
Mostly sealed terrariums rarely ever need to be watered. If you have glass covering the lid and are misting regularly, your tank probably only needs light watering once or twice a month. The easiest way to check when to water is to stick your finger into the soil, you want it to slightly dry out below the surface before watering. If you have a screen lid and low room humidity your tank will need to be watered more frequently, again check the soil with your finger before watering the tank. Looks can be deceiving and its always best to check before potentially overwatering your plants.
Bleach serves a useful purpose in horticulture, though I think this has resulted in lots of misunderstandings as it applies to terrarium use. Plant propagators use a bleach dip on cuttings for some more advanced techniques such as tissue culture and leaf cuttings in order to kill off any fungus or bacteria that may be present on the plant which would ruin the cutting. Bleach could also help kill off chytrid fungus if you were obtaining plants from a tank with contaminated frogs, though the plant itself wouldn’t be a carrier for the fungus. Bleach however isn’t effective at cleaning off pesticides from a nursery, nor does it effectively kill insect pests. Commonly used nursery pesticides fall into two categories, contact and systemic. Contact pesticides do exactly as stated, they kill pests on contact, if the spray doesn’t land on the pest, it doesn’t die, and the pesticides eventually wash away from irrigation. Systemic pesticides are a bit more difficult to get rid of since they actually absorb into all the parts of the plant, there is no way of washing them off since they’re now part of the plant, you just have to wait for them to wear off. Bleach is no more effective at washing off contact pesticides than normal water is, and it will do nothing to get rid of a systemic. If you want to make sure you get off all the contact pesticide possible on a plant, just add a drop of dish soap (not too much since soap will also damage plant tissue) to a large bowl of distilled water, the soap helps break the surface tension of the water, ensuring it gets into every nook and cranny of the plant. Only submerge the top half of the plant in the soapy water, the roots are best washed off with plain lukewarm water to avoid damage. As for insect pests and bleach, I have personally witnessed scale, whitefly, mealy bugs, and snail eggs surviving a 10% bleach soak. Your best bet against plant pests is to carefully inspect plants before purchase, especially where the leaves meet the stems, as bugs like to hide in sheltered areas. If purchasing plants online, do your research first and make sure you’re buying from a reputable source with bug free plants. If you do have the misfortune of ending up with an infested plant, make sure to immediately put it into quarantine and treat. A plastic storage tote with a clear plastic lid is great for a temporary holding terrarium until you can make sure all the bugs are gone. For just a few spots of scale or mealy bug, a q-tip with rubbing alcohol used to dab directly on the bug will dissolve the bug’s waxy covering and kill the insect. For other pests or more widespread infestations you can always resort to insecticidal soap or neem oil, both of which are contact pesticides which can easily be washed off with water before returning to your tank after quarantine is over. At least several times a week I have the misfortune of hearing from someone who has killed or seriously burned their plants with a bleach dip, usually after taking advice from a forum or individual with no horticulture background or knowledge. Unless for the several scenarios listed above, I strongly advise against doing bleach dips on plants for your tank. We deal with many sensitive species and even under the best situations many will not survive a bleach dip, and in most cases, there was never a good reason to do one in the first place.
The most important aspect of lighting for tanks is lumens and kelvins. For a nice white light for a planted tank, look for something in the 6500-kelvin range. How many lumens you need is a bit trickier to figure out, it all depends on the tank size and the lighting needs of your plants. Plants with high light requirements are going to be bromeliads, especially red colored ones if you want to prevent them from turning green, and some other epiphytes that would naturally be growing up high in the forest canopy. Low light plants consist of what would be hiding on the forest floor such as ferns, Selaginellas, Peperomias, some aroids, and mosses.
Soil mix, using coco fiber
Normal potting soil and coco fiber are not suitable substrates for a planted tank as both hold too much water. In such an enclosed, damp environment, air spaces around the plant roots are just as important as moisture. An exception would be Pothos or other plants that can grow in boggy soil or plain water, these can be used in tanks that contain coco fiber, such as a grow out bin. In a tropical tank, ABG (named for the Atlanta Botanical Garden, where the recipe was created) is ideal as it mimics a more terrestrial version of an orchid mix, it drains incredibly well, and also won’t break down quickly in high humidity. Not all versions of ABG mix are created equal and some have substituted lower quality ingredients. Some sellers throw in cheap bark mulch that can break down quickly while higher quality mixes use orchid bark or Orchiata. A good mix will contain peat moss, horticultural charcoal, long fiber sphagnum moss, orchid fir bark, and tree fern fiber.
Carnivorous plants aren’t very suitable for an inhabited terrarium. Many of the carnivorous plants commonly available require full sun and a dormancy period, conditions difficult to replicate in a tropical terrarium. Fly traps will have their traps constantly triggered by animals, causing the plant to eventually die. Nepenthes will outgrow a tank rather quickly if it’s doing well, since they are large tropical vines. Pinguiculas and other sticky candidates will get gummed up by the tank inhabitants and feeders, creating a mess for both your pet and the plant.
Most moss you see sold in large bags or sheets is collected from temperate areas of the country, meaning areas that normally experience a yearly freeze. While it can look great in your tanks for the first couple of months, the conditions for it to grow are completely wrong and it will start to brown and die off. If you like the look of moss in your tank, either hunt down some tropical moss species or try tropical plants than can replicate the moss look in your tank. Genuine tropical moss can be hard to find for sale, usually someone that has a greenhouse with orchids or other tropical plants has it start sprouting up on the floor or on plant pots. I always tell customers who get some in pots they buy from me to scrape the moss off the top layer of the soil and throw it in the blender with some RO water, then use that to paint where they want the moss to grow in their tank. Once established it takes off quickly. Tropical groundcover plants that can replicate the look of moss are Selaginella krassiana or Selaginella uncinate, two types of club moss, and also Peperomia emarginella, a tiny creeper with green and white leaves. Dwarf baby tears (Hemianthus callitrichoides) is another great tiny plant that can be grown emersed in a terrarium as a groundcover.