My first orchidarium was a small 29 gal fish tank. It has a false bottom so there is always about 3 in of water below. The sides and bottom are made of egg crate and have foam on them. They are covered with a mix of Peat.
The peat is mixed with a concrete bonding agent found in most large chain hardware stores. This makes a peat paste that is spread on the walls and floor. It takes about 2 weeks to harden but it is waterproof and holds the peat together but also allows the peat to wick and hold water.
I have a pump hidden on the inside of the tank that pulls water from the false bottom and pushes it up into a hub that sends it out to 5 small hoses used for drip systems where the water flows down the walls.
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I made the hood out of some extra bamboo flooring I had and lined the interior with aluminum foil. I then purchased a cheap light fixture and wired it to a plug. The lights or bulb compact flourescents.
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The fan is a computer fan purchased from Radio Shack.
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The fan needs other parts to work. It's very easy to wire. I wired my fan to a dimmer which will slow down fan speed but that is not necesary. The wiring is enclosed in a plastic box.
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You need a voltage adaptor that converts 110 power you have in your house to what your fan needs. The volts must match the fan speed and The people at Radio Shack know all of that so don't be shy about asking.
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Now, I made fake roots for the walls and floor like a jungle floor. I mixed some mortar with the concrete bonder and peat. I rolled them and stuck them to the walls. After they dried, I used a product called Patio Paint. It comes in small bottles and is waterproof. I got them at WallMart.
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Terrarium hood
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Whole terrarium
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Open waterside in Terrarium
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I think that is about it. Now, after having this terrarium for almost 2 years I would not do the 'Wet Wall' again. Algae forms too easily on the peat where the water is always dripping. What I would do is get an ultrasonic fogger instead and hook it to a timer. The fan should be pointed at the front of the terrarium to stop it from fogging up.