Thank-you Charley for rekindling one of my fond "projects" for the near furure i.e. a Paludarium ( one "L" , I think, at least over here). Our local native fish association (ANGFA) has been involved in a number of shows and displays involving not only natives but general aquarium fish as well as specialty groups such as Cichlids. There has been a definite evolution towards making these visually attractive to the public as well as providing a more secure habitat for the tank inhabitants.
Various combinations of materials have been tried to construct backgrounds that are lifelike and non-toxic - from fibreglass and concrete to siliconed rocks and gravel. At present humble styrofoam is the material of choice as it is cheap, available in a range of sizes in sheets and blocks, easily shaped ( by saw, wire-brush, electric soldering iron etc) and essentially non-toxic.
The desired shape , heat sealed with a hair-dryer or paint-stripper, is coated and tinted with a variety of agents ( I mostly use Ormonoid, a bitumenous sealant for water tanks for human use) and surface textured - usually while the "paint" is still wet the sand, gravel, crumbled peat moss etc is thrown or pressed on. The finished 3-dimensional backdrop can incorporate such features as surface pockets ( for planting marginals), planting pockets at various levels for other plants as well as caves and overhangs.
We are still considering a sealing coat outside the texture coat to stop some of the wear and tear on the surface. The finished product is then silasticed into place and sealed all round the edges to prevent ingress of foreign material and inhabitants. The final appearance and "naturalness" is only limited by the imagination and persistence of the producer. We have done some superb Paludaria incorporating built-in waterfalls and back-drop filtration all driven by powerheads and standard aquarium equipment.
A variety of epiphytic emerse (ferns, orchids, bromeliads etc) and submerse (e.g. Microsorium, Bolbitis) plants will thrive attached to the walls themselves and plants with all 3 forms ( underwater, floating and aerial) of habit can be displayed to advantage.
Charley's cut-out front could be useful to avoid the problem of front-glass condensation interfering with clear viewing. This whole Paludarium thing opens up a whole range of challenges and hopefully contributors to this list have some of the answers.
Bruce Hansen. (ANGFA)