Thursday, June 19, 2008

Setting up a custom Wardian Case

This Article documents the thought process involved in designing and setting up a large custom Orchidarium. After following a lot of threads on various internet boards, I decided to construct my own custom tank (or, as it turned out, having it constructed for me.)

Objectives for the new Orchidarium

Need a tank large enough to house an expanding collection of, mainly, miniature species orchids. These will be low-light, high humidity/moisture species.

Most of the plants will be mounted and hanging, as in stick or cork mounts.
Need an environment that allows low maintenance for the plants. This means I want to be able to ignore plants for at least a week at a time. Occasional fertilizing is understood, but daily is not going to make it.
Must have an environment where excess moisture drains away by itself, misting is taken care of regularly, light is not a problem, there will be places for lower wetness plants and higher wetness plants, and air movement is controlled over 24 hour period.

I desire to use 48” T5 fixtures as the only source of light. Lights will be timer-controlled.

Locating tank in basement where ambient temps are approx. 62 degrees F at night and 67 degrees F day during winter months will moderate temperature. Temperatures during summer months will be approx 65-70 degrees F at night and 75-80’s during the day. Cool to Intermediate growers are the best choices. A few spp on the edge of being warm-growers are also a possibility.

Tank should be easy to care for by non-orchid grower for periods of up to a month or more. My caretaker, while I am away, is not an orchid specialist.
Esthetics is NOT the primary issue – casual visitors will not see this tank. The tank is for hobby purposes and function is more important than esthetics. Quality of construction is important in order to eliminate future problems such as warping, separating of seams, etc.

Easy access to plants for watering/fertilizing (as infrequent as that might be) is a must.

After consideration of the objectives, I planned, re-planned and re-designed the tank. I decided to go with Paul at for fabrication. He was patient with me as I experimented with my retrofit aquarium and fine-tuned the misting and other requirements.

Retrofit Aquarium as test subject

I retrofitted a large aquarium by adding an acrylic riser, 8” high, siliconed onto the top of the aquarium. This is where all the fittings and holes were made. I settled on a Mist King misting system driven by their hi-end pump and with 3 deluxe nozzles. I am using a 5-gallon drywall compound bucket as a reservoir, where I have R.O. water stored. The system uses a 24-hour timer to set “day” and “night” and an interval timer plugged into the 24-hour timer. Through experimentation I have settled on 5 seconds of misting, every 3 hours during day cycles, and no misting during night cycles. The 12 volt 3” fan inside the tank runs 24/7 and disperses the mist during the day, directing most of the mist towards the moisture loving plants, and then serves to dry off the plants at night. A second fan is mounted outside the tank to blow away some of the heat generated by the T5 light bank. The top of the tank is simply a glass storm window, which helps absorb some of the excess heat from the lights. Access to the tank is by raising the light bank, disconnecting the outside fan, and removing the glass top. As moisture collects below the raise grating in the bottom, I have been removing it manually with a turkey baster. The stick-mounted plants have responded tremendously to this environment. The Cischweinfia, which I had previously not been able to keep growing well, have also responded.

Setting up the new Orchidarium

To control air circulation, and heat, I am using 2 fans – one inside the case circulating inside air. The second is mounted outside the case on the T5 light bank to help lower heat loading. The inside fan runs 24 hours a day and 7 days a week (24/7). The fan on the T5 light bank runs only when the lights are on to dispel heat. I experimented with a through-wall fan running at night but opted to not run that fan at all because it wasn’t necessary. The inside fan does the job, after the misters quit running, to dry off the plants sufficiently to deter mold.

To control watering and humidity, I am running the same Mist King system, keeping the same 5 seconds on - 3 hours off cycle from the retrofit aquarium. The through-wall drain runs excess water/fertilizer down to a storage tank below the Orchidarium. From here, it can be re-used outside during summer months, or discarded in winter. But it automatically drains excess fluids. I have found that with this tank, the humidity stays much higher than the retrofit tank did. I suspect this is because it is sealed better. I rarely got humidity readings above 88% right after the misters had run in the retrofit aquarium. I now get constant 90 degrees + readings with same instruments even hours after misting. I suspect I can go 4-5 hours between mistings and still maintain same readings.

I mounted two thermometer/hygrometers inside the tank – one near top and one near bottom to see if there was any difference. I got higher temps on the upper gauge (as you might suspect – it was closer to the lights) yet I got lower humidity readings. Typical readings during a normal day will be 70-71F/91% top gauge and 69-70F/96% lower gauge. This is to be expected. With relative humidity, as temps go down-moisture holding goes down, so relative percent goes up.

The shelf over the door on the left side provides a bit more light than is available elsewhere in the tank, probably in the neighborhood of 1000-1500 foot-candles. Also it tends to be lower wetness (same humidity, but no direct misting) and is meant for those plants in baskets of sphagnum, or in pots, that also need a bit more light than the mounted plants and don’t like wet roots.

Physically removing each plant and dunking in fertilizer solution handles the weekly fertilizing. While labor-intensive, this keeps solutions off acrylic walls and the tank walls stay cleaner. It also gives me a chance to inspect each plant for signs of mold or rot. These maladies are handled with Physan 20 spray, or Thiomyl, as they occur.

Setting up the tank – construction steps

After unpacking the tank, the first step was to locate holes for fan mounting screws and mount the thru-wall fan. I used stainless steel screws and nylon nuts for this task. In the end I opted to not use this fan (at least right now.)

Next was to assemble the small upper shelf from “egg crate” material meant for fluorescent lighting fixtures. I used aluminum channel siliconed to the long edges to stiffen the shelf.

Next was to cut and fit the bottom shelf, also made from egg crate. I am resting the shelf on a series of 2 ½” high plastic pots. This creates a reservoir for excess spray water. The Mist King bulkhead fitting at bottom of tank will assure water never accumulates deeper than about ¾” before running down to an outside reservoir.

Next step was to cut a sheet of cocoa fiber matting to fit most of the back of the tank. This serves to hold some of the mist water during the day as well as provide a more esthetic background surface. In addition a few mounts may be hung from the matt. The matt was attached to back using RV grade silicone (waterproof).

I dry tested the tank with a wet sponge and found out it held humidity very well. Even though I had originally planned to run a “drying” fan at night, I decided to eliminate this step for now. I moved the tank into it’s final resting place, under the existing T5 bank, and fired everything up. Here are the final (as of 5/1/07) specs for the tank:

Size: 36”Lx20”Wx30”H (91 cm L x 51 cm W x 76 cm H)
Construction: mix of clear and black acrylic
Day temps (Winter): 69-72F (20-22C)
Night temps (Winter): 59-62F (15-16C)
Relative Humidity: 90-97%

Sources of components

Misting system and interval timer
Fiberglass rods for hanging
T5 light bank (Sunlight Supply, Sun Blaze)
24-hour timers – Home Depot
Heat absorbing glass under T5 light bank – local glass store
Hygrometers -


ChrisC and JonJ said...

Sounds a little complicated to me.Maybe I could learn something?

Anonymous said...

Oh I am very interested now. I am in the process of setting up a Wardian Case of sorts in my basement. I grow mainly Neofinetia falcata, but also other mini vandaceous plants and a few odds and ends. I will be reading your blog often. You have plants I want to try.