Introduction: Terrarium / Vivarium Waterproof Rock Work for Frogs and Amphibians

About: I am a former zookeeper. One thing you may not know, zookeepers often have to make their own specialized tools, enclosures and supplies. It's just part of the job, because there aren't really any box stores …

This instructable will guide you through the steps required to build a customized animal habitat, which will provide your exotic pets with a healthy and stimulating environment.

The final animal enclosure consists of a waterproof glass aquarium with a large planter, vertical climbing wall, and water feature at the back, plus a smaller planter at the front with a false floor suspended between the two planters, above a water reservoir containing a filter pump and heater.

It is not cheaper to do this project than to buy pre-made plastic and foam stuff from the pet store. It is better. I'm not going for cheapness - I'm going for quality of life for my animals. The fact is, pet stores don't sell stuff like this anyway.

The project outlined here is for amphibians, which require a high level of humidity, so the rock work is constructed entirely from hydraulic cement.  Hydraulic cement is also advantageous because it does not leach any compounds into the water or soil after it has cured, and it does not affect the pH, unlike other types of cement.  (Added note:  Don't ever depend on a statement like this for the safety of your animals or plants.  If you have a very sensitive animal or plant, you should test parameters like pH for yourself to make sure that the parameters begin safely and remain stable over time.)

For this project, I focused on providing a maximum amount of usable and stimulating terrain for the type of animals to be housed, specifically poison arrow frogs.  It is possible to create realistic-looking rocks with these materials, but in this project I am less concerned with appearances and more concerned with useful habitat.  I think you will agree that the final look is attractive, even without spending any time trying to make the rock work look "realistic".

Because I live in a very dry area, where the humidity is only 40% on a good day, I determined that a subfloor system, suspended over a large reservoir of water would be the best way to keep the humidity up and reduce the number of times I need to add water to the filtration system.  For the final setup, this tank ended up with a 3.4 gallon reservoir and a base humidity level of 74% even without misting.

Materials, tools, and time

Be forewarned: You will get dirty! It is impossible to work on a project like this one without making a mess. Don't try it on the kitchen table.

Very important: If you rinse hydraulic cement down the drain, it will harden in your pipes and ruin your plumbing. It will harden under water! Even small amounts of the powder will collect together and permanently block the drain. No plumber's snake or drain cleaner will ever remove it. You will have to remove the entire pipe and replace it. Throughout the project, I used disposable gloves and also removed as much of the material from my hands and arms as possible using paper towels, before I washed in the sink. Gloves will also protect your skin from the chemical reaction and abrasive qualities of the hydraulic cement.

Free time (see below)
Aquarium or terrarium enclosure (I used a 29 gallon aquarium.)
About 25 lbs of hydraulic cement (Pictured are two brands: Ace hardware and Quickrete.)
Waxed paper or saran wrap
Cellophane tape
Rubber gloves (lots of rubber gloves)
Small planters, easy to cut with scissors
Water pump with filter
Flexible tubing, compatible with your water pump

Heavy duty marker
Tub for mixing cement
Robust water container (It will get dirty.)
Razor blade for cleaning the glass

Time spent:
Day 1 - Begin the back planter - approximately three hours
Day 2 - Add interest and strength - about six hours
Day 3 - Finish the back planter - around five hours
Day 4 - Complete the front planter - at least six hours
Day 5 - Seal the planters - several hours
Day 6 - Complete the water feature - four hours
Day 7 - Complete the subfloor - around four hours
Day 8 - Test the water feature and planters - about an hour
Day 9 - Add plants, water, and light - about two hours
Day 14+ - Add animals - thirty minutes

Step 1: Day 1 - Begin the Back Planter

I began with the large planter and rock work of the back wall, because it was the largest and most complex of the pieces to be constructed.

Lay the aquarium or terrarium on its side to make it easier to work with.

Because the final design will be incredibly heavy, you need to make sure the rock work is removable one piece at a time.  While working with the cement, always tape a lining of waxed paper or saran wrap firmly in place, so it doesn't move around or fall down a lot and drive you crazy.  This lining will be removed after the piece is completed and will ensure that the cement doesn't bind itself into your terrarium permanently.  It may seem like a hassle, but if you don't use a lining, the cement WILL stick to the glass.

For specific instructions on mixing the cement, look at this instructable:

Mix the hydraulic cement a little at a time and build up what will be the back wall until it is the shape you want.  Smooth new cement into the existing pieces to prevent gaps and leakage.  Add new cement while the prior pieces are hardened enough to keep their shape, but still damp.  This is important for strength and to prevent leaking later on.

I was able to make the back wall very thin for this planter, because I later added horizontal ledges and ramps, which added to the structural strength.  The fewer ledges and ramps you are planning to add, the thicker you should make the back wall. 

Build up the bottom of the planter, making sure to seal the bend very well.  Make the bottom as robust as possible.

Cut the small plastic or peat planters and place them where you like them, then cement them in, again working in small amounts of cement.  Leave at least one drainage hole unobstructed at the bottom of the small planters.

This step of building up the basic shape of the back wall and cementing in the planters took approximately three hours for me.

Step 2: Day 2 - Add Interest and Strength

Sketch the layout of the ledges and ramps until you settle on the one you want.  Transfer the layout onto the cement with a heavy duty marker.

Build up the shapes slowly, making sure to curve them upward or keep them as level as possible.  Make them just large enough for the animals that will be housed in the enclosure.  I was able to make them very thin and delicate because the frogs that I will be housing are very tiny.  They are also very agile and climb quite high in the trees in their natural environment, so I did not have to worry about making ramps too steep for them to climb.

If you are going to house a larger or less agile animal, you should design accordingly with wider and more robust ledges and shallower, easier ramps. 

Step 3: Day 3 - Finish the Back Planter

After the ledges have cured completely, probably overnight, you can stand the aquarium upright and complete the front and side walls of the planter.

I designed the tank to have a large reservoir of water for the waterfall, so I built the planters quite deep.  Deep planters will also allow better growth of live plants.

After the front and side walls have hardened for about two hours you can carefully remove the planter and the lining.

This step should take around five hours all together, because you will need to wait between layers as you build up the vertical wall.  Building a free-standing wall like this one is much more difficult than building against the glass, as you will find out.

Step 4: Day 4 - Complete the Front Planter

Lay the aquarium or terrarium back on its side and line it again.  Make sure it is clean before you start.

Build up the front and side walls of the smaller front planter to the same height that you made the back planter, making sure not to leave any gaps or cracks in the cement.

After the front and sides have cured for about two hours you can gently stand the aquarium upright and add the final wall.  Be sure not to leave any gaps or cracks where the planter might leak or break.

After the whole thing has cured enough (about two more hours) you can gently remove the planter and the lining.

This step of building the smaller planter will take at least six hours all together.

Step 5: Day 5 - Seal the Planters

Fill the planters with water and mark any areas that leak, using a heavy duty marker. 

Empty the water and patch the marked areas with a soft mix of hydraulic cement.

This step took two days for me, because I discovered more leaks after I thought I was already done.

It may take two or more immersions for you to find all of your leaks, but if you just keep at it, you will eventually find them all.

Step 6: Day 6 - Complete the Water Feature

I lined the aquarium, then put the back planter in place, set the hose in where I wanted it, lined over the planter and hose, then began building the water feature over and around it for an exact fit.  It is easier to use saran wrap as the lining for this step.

Don't allow the new feature to overlap the existing planter too greatly, or it will be difficult to remove them and put them in place later.

I overbuilt the bottom, making it thick and heavy, in order to add stability, since this piece will be relatively tall and narrow.

After the cement hardens completely, pull the hose back until the end is level with the front of the water feature.  Don't try this while the cement is the slightest bit damp, or you could break it.

It took about 4 hours for me to complete the water feature, then 24 hours for it to dry completely.

Note added later:  When building the water feature, I pinched the hose too much and eventually discovered that it interfered with the functioning of the filter.  So, I had to build a new fountain from scratch.  Since I had to re-do it anyway, I re-designed it as a hollow feature with room inside for the water-pump.  This brought the access lid up to the top of the enclosure, in the corner, so the water pump is much easier to maintain.  I no longer have to open the cage lid as far, nor do I have to remove a piece of the floor to reach the water filter.  This isn't technically necessary, but it could be helpful, depending on the type of animals you are housing, their sensitivity to disruption, and their propensity for escape.

Step 7: Day 7 - Complete the Subfloor

Set the tank up with the planters and water feature in place.  Add the filter and other hardware that requires a power cord.  Direct the cords where you want them and tape them in place.  Fill the rest of the tank with sand, up to the level of the planters, where the subfloor will sit, then cover it with saran wrap. 

Build up the subfloor in sections, so that you can remove key pieces to access the filter easily.  Small, interconnected pieces work better than large ones.

You WILL have to access the filter at some point.  They have to be cleaned periodically and at the very least, they have to be replaced when they break.  This is the reason that I made no attempt to build the filter into the waterfall feature and why I have chosen to leave the cords visible at the back of the enclosure.

Start at the edges of the tank and create a series of solid, but manageable pieces.  After you finish one piece, lay a piece of saran wrap over it before building the next piece.  In this way, you will have interlocking but separate pieces that can later be removed individually.

Make sure that you create the subfloor pieces to set on top of the existing planters.  Resist the urge to wrap the edges over the top of the planters.  If you do that, you will likely have to break either the planter or the subfloor in order to remove it.

After some initial tweaking, I can now access the water filter in less than a minute, by picking up two pieces of subfloor.  With filter cleaning and replacement in mind, I also made sure that the tubing for the waterfall is easy to attach and remove from my filter pump.

It took me about three hours to build the initial subfloor and another hour to tweak the pieces and replace those that could not be removed and replaced easily enough.

Step 8: Day 8 - Test the Water Feature and Planters

Empty out the sand after the subfloor has hardened, and reassemble the tank with the water pump in place and the waterfall hose connected.  Let the water pump run for a while and watch to make sure your planters do not fill with water.  Some seepage is fine, but you want to make sure that your plants will not drown.

If the waterfall sprays outward, you can add a hood of hydraulic cement over the top of the outlet, to direct the water downward.  Also, you can add cement to other areas of the feature, to direct the water where you want it.

Note added later:  Alternatively, instead of a suspended subfloor, you can put in a raised bed using the techniques described here: /.  The key is to leave a large area which can fill with water, to keep the humidity level up and allow for gentle and even heat distribution.  You will have better luck with clean water and filtration if you can keep the soil and mossy substrate above the level of the water.

*These frogs can drown, so it is important not to let them access water that is more than an inch or two deep.

Step 9: Day 9 - Add Plants, Water, and Light

After you have established that your pump works and your planters are functional, go ahead and plant. Keep in mind that the plants are going to grow, so get just a few plants and split them up around the tank. A little goes a long way.

In the photos shown, you can see how full the tank was after I split apart one small fern from a 4" pot, one small creeping fig from a 4" pot, one bromeliad that had two offshoots from a 4" pot, and a couple of small creeping thyme plants from 2" pots.

Remember to plant appropriately for the species you are housing, using no chemically treated soil or fertilizer.  I used organic soil mixed 5 to 1 with clean vermiculite, then topped it with a mulch of shredded red cedar.

Get the enclosure completely ready for your animals and let it run for several days with no animals in place yet.  It is very important that you discover any flaws in the system before you put animals into the environment.

To accommodate the temperature requirements of my frogs, I put an aquarium heater under the subfloor, with the water filter.  Often, if you heat the water to the correct temperature, the ambient heat in the enclosure will rise accordingly.  I added a thermometer and humidity gauge, so I can be sure the habitat remains suitable for my animals.  I also added a low wattage, full-spectrum bulb for the health of the plants without too much brightness for the frogs.

Step 10: Day 14+ - Add Animals

Wait until you know your water filter is working properly and your planters are not leaking into the water reservoir before you add animals to the tank.  Waiting a few days or a week will also allow the plants to get established before any animals get to tear them up.

Ordinarily, I quarantine adult frogs for 90 days, however these frogs were subadults when they arrived, so they were very small - only about the size of a dime.  I let them grow for several months in the smaller and safer quarantine tank, before moving them.  As adults, they are still only about 1.75 inches long, and they move like greased lightning, so transferring them is quite a risky and delicate operation.

How to assemble a quarantine tank:

I took the time while the animals were in quarantine to debug and modify the filtration, plants, lighting, and lid design so that it would work best for me.  I basically re-built the entire waterfall section of the tank, and made it easier to get to the water pump, so I no longer have to remove sections of the floor to reach it.  You just have to figure out what will work best for your situation and be prepared to make modifications when necessary to ensure the safety and health of your animals - even when it is a pain in the butt.  Rebuilding the fountain was definitely a hassle, but it was worth it.

Below are photos of the frogs in their fancy frog-condo, at their feeding station.  You will find that even "simple" animals, such as frogs can be habituated to go to a certain location when they are hungry.  Simply feed them in the same location every time, and they will begin to associate that area of their enclosure with food.  If you notice that the animals are staying in the feeding area for long periods outside of feeding times, you can be sure that they are hungry and you should increase the amount or frequency of their feedings. 

I used a shallow feeding bowl in the front corner of their quarantine enclosure, and they came to associate that location and the bowl itself with feeding.  When I transferred the animals to their larger enclosure, I moved the same bowl into a similar location.  Within 24 hours, they had recognized and approached their new feeding station.

You can also use habituation to help keep tabs on your captive population and improve the security of the enclosure.  By signaling the animals with a flashlight and a certain sound before each feeding, I have caused them to associate those events with food.  Any time I would like to count them or get a good look at their physical health without opening the lid, I signal them for a feeding, and they inevitably will approach the feeding station. 

By signaling a feeding before opening the lid, and waiting until the animals come out into the open, I can be sure that I'm not putting them at risk when I open the lid.  Relying on food items to draw the animals into the open would mean that the lid would have to open before the animals could be located.  This is dangerous to the frogs because they are so small that they can easily disappear into the top of the rockwork or into the shadow under the edge of the lid, where they could escape as soon as it's opened even a small crack.