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
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
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
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: http://www.instructables.com/id/How-to-mix-hydraulic-cement-for-sculpting/
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.