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SOIL MIX FOR TERRARIA - Paula Morris
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Each layer has a specific purpose. The first three can be used with any type of vivarium. The fourth layer, the soil mix, can be altered to suit your need: tropical, woodland, or desert. Don't be intimidated by thelength of this post. It's really a very simple mix and easy to assemble. To furnish your vivarium, work from the floor up. You will be almost duplicating, in miniature, the various layers found in the earth. You start with:
DRAINAGE MATERIAL. Use 1/4"-1/2" gravel, small stones, or lava rock (which is great because of the light weight). It usually looks better if you stick to natural colors like beight, brown, gray, etc., because the gravel will show through the glass. Bold colors tend to detract from your overall design. When you lay down the drainage material, the depth proportion is 1/3 drainage material to 2/3 soil mix. Usually the minimum is 1/2" and the maximum you would use is 1-1/2".
CHARCOAL. Use horticultural grade charcoal if you can find it; it's cheap and already cleaned and bagged. Otherwise, you can use crushed barbecue charcoal; just make sure it's quite fine, no more than 1/8"-1/4" pieces. Sprinkle roughly a double layer directly on top of the drainage material. Some will stay on top, and some will work down between the stones. This will help keep the water "sweet" instead of letting it turn foul. There's no smell in the substrate mix when you add charcoal.
SOIL SEPARATOR. This is a step most people have never heard of, but it makes a tremendous difference in the success of maintaining a healthy substrate for your plants. Basically, it prevents the soil from sifting down onto the drainage layer. A soil separator needs to be something that won't rot, is porous enough to let water through but not so porous as to allow soil to filter through. The best thing I've found is rolled fine mesh fiberglass from the home supply. It's available by the yard, resembles open weave fabric, and is more flexible than window screening material, but either works. I fit this in a single piece flush with the sides of the terrarium because there's less likelihood that the turtle or tortoise will claw it aside and allow a lot of soil to trickle to the lower layers. In a pinch, you can use overlapping layers of women's pantyhose, but if your turtle or tortoise does any digging at all, it's going to get messy pretty quickly.
SOIL MIX. This is the final (top) layer of your substrate. Now's the time to add the tropical soil mix recipe below. The amount is going to depend upon the height of your tank, meaning how much of your animals' space you can afford to give up to the plant's roots. If you're not including plants, don't worry about this. Generally, though, you will wind up with about 2-1/2" to 3" of soil. Here's the soil mix: 3 parts of sterilized potting soil; 2 parts sand (NOT seashore sand, it's loaded with salt!); and 1 part peat moss (NOT sphagnum moss).
All these ingredients should be available at local home centers or nurseries, and amounts adjusted to the species' needs. I do not advocate much sand, even for the arid-dwelling animals. But they don't seem to eat it when it's mixed with the sterile soil and peat.
If you cannot find sterilized potting soil, get regular potting soil and sift out the perlite or vermiculite (small white spongy balls) and the larger wood fragments. I have both a hand sifter (for baking) and a frame of fine mesh screen for sifting large amounts of soil. Sifting takes awhile, but there must NOT be any perlite or vermiculite in the soil mix. What you get is powdery and soft.
The soil mix is rich enough in nutrients to sustain any terrarium plants without causing rampant growth. Do NOT use fertilizer; it'll be toxic to your animals. It only needs to be raked to keep the surface tidy, and the soil replenished every few weeks. The surface can be misted or some water poured into the soil mix to keep up humidity.
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