Help! My 3 day old terrarium already has mold :(

[DesignerofBeauty]

Hello Everyone,

Thanks to the wealth of information found in this forum, I have built my very first orchid terrarium. I purchased all of the orchids and built the terrarium Tuesday. Already, one of the mounts has mold on it. I already used some tissue to remove the mold. In addition, I put a few drops of Physan 20 in a plastic cup and filled it with some water. I used a cotton ball and Q-Tip and applied the Physan to the areas where there was mold. Unfortunately I didn't photograph the mold. It was snow white and in circular patches.

Could someone please let me know what I'm doing wrong that caused the mold to appear in three days?

Here's some information on the setup: I have a 8inx8inx12 inch exo terra nano. It's a very very tiny enclosure. To construct the terrarium, I used the plastic egg crate lighting panels. The panel was cut to the size of the terrarium. I used Pond & Stone Great Stuff Foam and sprayed the panel. I trimmed the foam to make it look neat. I then used Aquarium Silicone and attached Hygrolon to the foam panel.

I bought a bunch of orchids from Andys. I removed the wire hanger. I secured each mount to place with a needle threaded with monofilament. I wrapped the monofilament around each mount a few times to secure it.

I have a false bottom. I used Exo Terra Bio Drain as a substrate. I put a Exo-Terra Bio Drain Mesh on top. On top of that I flattened Sphagnum moss to create additional protection. On top of that, I put ABG.

The terrarium's light source comes from a regular LED bulb you can get at any store. It's a 75W equivalent bulb that runs on 12W. The bulb is powered by a hood that Exo-Terra creates for the nano. When the hood is placed on the terrarium, there's a 1.5 inch gap which I assumed is plenty of air circulation. There's also venting on the front of the Exo-Terra, but it's covered by my ABG.

The terrarium's temperature ranges from 75-85 degrees. The hygrometer I've used says that the humidity is around 50%, but I've doubted that figure. I've used another hygrometer that reports higher humidity.

I use distilled water and a mister to spray the terrarium once the plants dry out slightly. All of my plants (with the exception of S. Fragrans) like to be kept moist but to dry out slightly. I've attached a few pictures to further help with my question.

Top Row (Left to Right): Schoenorchis Scolopendria, Stereochilus Brevirachis, Schoenorchis Fragrans, Dendrobium toressae, Mediocalcar Decoratum.

Middle: Gastrochilus Japonicus and Pleurothallis Leptotifolia

Floor: Dyakia Hendersoniana and Angraecum Distichum

The mold was present on the bottom edge of the S. Scolopendria mount (top left hand corner of the photo) where the edge of the mount meets the moss. I also found some on the back (where it touches the hygrolon).

I plan on getting a computer fan to help rectify the issue. My thoughts on why the mold developed: Maybe I need sprintails? Or maybe the hygrolon keeps the back of the mounts too moist, creating mold? Or maybe I've attached too much moss? If anyone has any advice, I'd greatly appreciate it!

Thanks for reading all of this