DIY Mushroom Ledges & Decor for Your Reptile Terrarium With Moldable Plastic

Make your own custom decor for your next vivarium build using moldable plastic! In this Instructable, I'll show you the basic techniques for using moldable plastic (it's super easy!), and then give you a few ideas of how you can use this plastic to make sweet perching spots, feeder ledges, and decor for your reptile's home. This is an ideal project for folks who are building out a whole custom vivarium with spray foam background especially.

If you don't have reptiles, these techniques work great for crafts too! You can mold your plastic mushrooms around LED wired string lights to make a little lamp, or make your own magnets for a metal noticeboard... anywhere you can dream of mushrooms, there can BE mushrooms, if you just believe in yourself! So let's get to it!

Please note: Links to specific products may be affiliate links. It doesn't cost you anything to use them, but it does help me with a small commission that... I'll probably spend on more moldable plastic, if I'm going to be honest about it.

For basic building, you'll need simply:

• Moldable plastic pellets. I've used InstaMorph, but there are tons of other brands now like ThermoWorx, Polly Plastics, and plenty of other brands.
• A pot with enough water in it to cover your plastic (I usually fill a saucepot about halfway)
• A fork or tongs to get your hot plastic out of the water
• A bowl of ice water

To build your mushroom or shelf directly onto a piece of wood, you'll also need... a piece of wood. Cork half-rounds work great, especially if they have some holes in them that can help you secure your mushrooms.

To build a magnetic ledge you'll also need:

• A feeding cup of the size that you want to fit your ledge
• Magnets (I like to use ones available from vivarium suppliers, like these from Pangea; get one with the black cap and one without for a complete pair. For larger animals, or animals that will grow large, I recommend two magnets to keep your ledge from pivoting!)

You can also use these optional supplies:

• Moldable plastic color pellets. InstaMorph, Polydoh, and Polly Plastics all have kits (PP has colors or metallics), and I'm sure other manufacturers do too. It takes VERY FEW color pellets to color your whole project... even just a few pellets go a long way. Make sure you consult the manufacturer's directions.
• Glow in the dark powder. I can't find any reliable information about whether this is reptile safe, but it is mixed into the plastic so I'd guess the exposure is minimal. Use in vivariums at your own risk! (If anyone has information about its safety, please comment!) For craft projects it's 10/10, I absolutely love to make everything glow in the dark.
• Reptile-safe 100% silicone. You might not need this, but it can be helpful to secure your mushrooms in spots where they want to wiggle around too much.

And a final note on the material: I don't recommend using any form of plastic implements (plastic forks, bowls, etc) or otherwise touching your hot moldable plastic against anything else that's plastic; some plastics it will stick to and never let go. Use materials like metal, wood, or ceramic for your various work implements and surfaces.

If you're making mushrooms for a custom vivarium, it's a good idea to plan out placement in advance so you can figure out exactly how you're going to attach your mushrooms to the background -- and whether you'll need to attach them to spray foam, a wood piece, or something else. A few things to consider:

If you have younger reptiles, don't plan for how big they are now, plan for how big they're going to be. You don't necessarily need to make all of your mushrooms very big, but placing them in clusters can be helpful for your reptiles to be able to spread out. In the first picture above, I went absolutely crazy adding mushrooms to the vivarium for my orange crested gecko, Newt. She didn't use the ones along the back wall because there wasn't a big enough surface area for her to drape herself on, but she did like that cluster right at the front. (The painstakingly carved cave system she never went into even once in her life. You live and you learn I guess?)

Consider where your reptiles might like to hang out, and make sure the clusters there are big enough to use. I added a single small mushroom to my gargoyle gecko Sputnik's vivarium near the top of the enclosure, thinking it would be decorative, but it ended up being a favorite spot because it was the closest point to the heat lamp. The photos are a story of increasing sadness as she grew too large to comfortably fit on it.

If you're adding mushrooms you don't want your reptiles to use, you can make them purely decorative with good placement. For instance, if you want strictly decorative mushrooms, you might make them too small for a larger reptile to comfortably use, or tuck them away in a spot your reptiles don't favor. In the first photo above of Newt's tank, the lowest mushrooms are a great example; as an arboreal species she liked to be higher up and didn't hang out on those. But always install your decor in a sturdy way, assuming that your reptile will at least climb on it in passing! You don't want it to come loose if they step on it.

If you have an existing spray foam background, you can add mushrooms to it after the fact. If you're just going to attach your mushrooms to spray foam, I recommend finishing the foam surfaces (silicone-ing and adding coir or whatever you're planning on), and inserting your mushrooms afterward.

Okay, let's make some stuff! The first step is to heat your moldable plastic.

Boil a pot of water on your stove. Once it's boiling, turn the heat down to a simmer, and then pour in some moldable plastic. A little goes a long way, and it's easy to add more, so start slow and remember that when you squish it together it's going to end up smaller than it looks.

When the pellets go fairly transparent, they're hot enough! Use your fork or tongs to grab the mass of them, and swish them around in the pot a bit to make sure you've got any stray pellets. They'll stick to each other as you move the glob around.

Lift your pellets out of the water and gently shake off excess water over the pot. You'll be tempted at this point to start molding, but give it a little time; there will still be hot water trapped inside between the pellets, and they'll be much hotter than you think. You can give it an experimental squeeze now and again, but don't handle it until it's fairly comfortable to touch.

You have more working time than you think, so don't rush and scorch your fingers!

(If you don't have a stove or prefer not to use a pot, you can also use water heated in the microwave, or hot water from a kettle. The stovetop method with a pot is just nice because you can keep the water heated while you work, which we'll get into a bit more.)

We're going to start with a basic hemispherical shaped mushroom. My geckos seemed to like this kind the best, and spent a lot of their days draped dramatically across them, and they look really cool.

Squish your plastic together so it's in a fairly solid lump and you're squeezing out any air or water pockets inside.

Then make a shape that's roughly a long stem with a big old blob on the end.

Shape the blob into that classic mushroom-y umbrella shape. I've always left my edges pretty rough, but if you wanted to make them more regular you could roll the edge against a solid surface. I use a cutting board for a work surface.

If you want to get REALLY precise with how your mushrooms look, like adding gills to the underside of the cap, that's totally doable! I'd recommend crafting your mushroom cap separately, and then attach a stem to it later. You could also use something like a small ceramic bowl as a mold for your shape while you're putting in the detail work.

Once you're happy with how it's looking, dip just the cap of your mushroom into the ice water. Wait until it turns fairly white, then pull it out.

Your stem should still be warm and pliable. Shape the stem into the position that you want, and dip everything except the very end into the ice water. You'll need to support the whole length of it carefully; this material is very pliable and saggy when it's warm. It's helpful if you can keep the end out of water, since we're going to further shape it, but if you need to dunk the whole thing or it's just gotten too cold, no problem: just dip it back into your pot of hot water until it goes clear again. Same goes if your bend sags in ways you didn't want, or something else needs adjusting: just give it a quick dip in the hot water to soften it up. Unless you need to make a big change, just a few seconds to get it to translucence should be good enough. The thicker and bigger your object is, the longer you'll have to re-heat it to get the core of it hot. (If things really go wrong, you can just throw the entire thing in your pot and let it all re-heat so you can start over.)

Now shape the tip of the mushroom stem into a shape that you can jab into your foam background. My first mushrooms I just made a sharpened pencil sort of end, but found that they rotated very easily under the weight of my animals, even when they were siliconed in, so now I prefer a sort of fin shape as shown in the photos. They'll still insert well enough through foam, but the upright fin shape keeps it from wanting to turn too easily. Don't make it too thin; you don't want it to snap when you're inserting it.

To install in your foam background, literally just push them in like tiny handcrafted shivs. See how well they stay in place; you can silicone them in or not, as you prefer, as long as they're staying put. If you have a cluster and want to make it really strong and reinforced for your animal to lay on, you can place all your mushrooms in such a way that they touch each other, and then use a heat gun to heat the surfaces a bit and stick them together. Or build a whole cluster as a single unit outside of the tank and then insert it after the fact.

If you want to have your mushrooms sprouting out of a tree instead, I recommend finding a nice piece of cork bark with some holes in it. Follow the same steps as above, but instead of shaping a fin with the tip of your mushroom stem, insert it through the hole. On the opposite side, you can flatten it down against the wood or preferably, if you're going to fill in behind the wood later with spray foam, make a fin or other stabilizing shape for the foam to fill in around and grip.

This can be an unstable configuration, so do what you can to minimize the chance that the animal will put their weight on the mushroom and cause it to rotate.

Having experimented with this a bit, I don't love this method for the hemispherical-type mushrooms unless you have a good-sized hole where you could insert a whole cluster through and then very firmly join the whole thing. Which leads us to the other option on wood...

This is a pretty cool piece of decoration and sleeping ledge particularly if you have smaller reptiles like anoles, mourning geckos, dart frogs, things like that. (I've found they're generally not quite big enough for larger species like crested geckos; you could certainly make some extra-big ones, but in my experience the bigger geckos just don't care for them much.)

Find a big, sturdy piece of cork bark. It's best if it has some holes and dips and things where you can sort of "lock in" the shelf mushroom. For this one I placed the biggest of the shelf mushrooms in a spot where I could squish some of the material through a hole to sort of anchor it from the other side.

Shape your heated moldable plastic into a sort of patty, then press it into the bark where you want it and do your best to make it mushroom-shaped. Channel the mushroom. BE the mushroom. Mine didn't come out all that impressive, but I have every confidence you'll do better.

Let it cool on its own (dipping it in water may make the wood expand enough to impact the fit of your mushrooms) and when it's all cooled down, give it a vigorous wiggle to make sure it's firmly placed enough. If it shifts around, you can try inserting a little silicone into any cracks that are behind it to try to bond it more firmly to the wood.

While this plastic can be re-heated and re-shaped as many times as you like, I will warn you that this type of mushroom is a lot harder to re-do. You can't really dip your entire wood piece into boiling water, so if it needs to come off you can try holding the parts you're able to dip in hot water, soften it up with a heat gun, or break it with pliers and then re-heat the pieces. There's some risk to your nice cork piece, so bear that in mind. If you find a better way to do this, please comment and post your own Instructable!

Alright, on to the feeding ledge! You can buy these commercially and that's probably easier, but what's the fun in that?

You're going to need your feeder cup and terrarium magnet for this. The magnets have polarity, so stick the plain magnet together with the one that has the black cap, and on the plain magnet mark the side that wants to join with the other magnet. I put an X on mine with a sharpie.

For these I used some of the colored pellets, so we'll get into techniques for that but first the basics of how to make the shape.

Heat a few separate piles of pellets. You can pour a couple of little separate clumps of pellets on opposite sides of your pot.

With one bunch of pellets, make a fairly thin layer to wrap around your feeder cup. I know I warned you about touching the hot moldable plastic to other plastic, but this seems to be fine, they don't stick together. Because I was keeping tropical reptiles and there was a lot of moisture, I left the bottoms under the cup open so water would run out easier.

Form your second bunch of pellets into a sort of strip, and wrap it around the existing plastic, building it up into sort of disc shape. (See the second photo above.) Keep doing this until you have the sort of shape you want. Make sure it's big enough for the reptile you want to use it with to sit on it while they eat!

With your fingers, flatten the side that you want to place against the glass, and press the magnet in. Make sure that the side you marked -- the side that wants to attach to the opposite magnet -- is facing OUT.

Now take that side where you've inserted the magnet, and press it against a flat surface to truly flatten it out. That will help it sit flat and level against the glass when you place it in your terrarium.

Let it cool a little, then pick it up while it's still a bit pliable, and pull a little bit of the plastic down over the magnet to hold it in place.

For the first one in the photos I added quite a few black pellets and ended up with basically a black shelf. For the marbled look in the second shelf, I had two separate piles of pellets: one just white, and one colored with a couple of pellets of black. I layered them over each other, folded them over each other again, then created the ledge as detailed above. That gave me the marbled look in the last photo above.

To finish the ledge off, I recommend a thin layer of silicone applied to the side of the ledge that will be against the glass. That will protect your glass from scratches, and also add some additional traction to hopefully keep the ledge from rotating. If you have larger animals, like adult crested geckos, you'll need to make the shelf much bigger, so use two magnets on opposite ends.

That's it!

I hope this Instructable has given you some ideas for your next custom vivarium build, and if you have ideas for improvements or elaborations on the idea, I'd love to hear from you in the comments!