what is an ideal interior fountain liquid

Viscosity would be more important than vapor pressure. You could also try maple syrup...sort of a slo-mo fountain.

The fly's would love ya.

ok i guess i could figure out how to deal with glycerin loving bugs in the fountain and feed them sweetened to my 3 pet firebelly toads. so no big problems here - just set it and do it. that will be done.

Vodka. But don't tell anybody; let it be an exercise in discovery learning.

until someone lights up a lighter or the vapors reaches a pilot light then......

Hello, I knew someone a long time ago that had a string art sculpture that used glycerin that flowed down nylon strings like droplets of rain in slow motion.

As to using water in your camper setting. As long as you had air exchange and stable air/water temperature moisture/condensation should be minimal.

To use glycerin, oils or other similar liquids would most likely collect dust, dirt and if spilled/splashed, stain surrounding areas.

In my camper in cold weather the walls collect moisture because there cooler than the air temperature. If cooking, or bathing the water vapor builds in the air then cools and condense on the cooler walls.[think drink glass with ice]

During times like above open an exhaust vent and open a window a small bit reduces the condensing effect some.

Other option would be to use a small dehumidifier where the moisture becomes an issue.

Otherwise your water wall should be a nice addition. When not in-use, traveling, gone during the week {used as a weekend place} or camper in storage drain the water from the tank.

the staining of surrounding areas might not be that bad as i like some stains present here and there. the surrounding areas are on the waterproof - stainproof side so that should be ok. the collecting dust etc might be ok to as that would collect the room dust - now i have to figure out how to filter the dust out or just leave it in and add some more vodka to make it flow better. i promise to send pictures when this done - eta 2 months maybe three.

Beer, has a lot of water in it.

Propylene glycol has a low vapor pressure and viscosity that is lower than glycerine.

Some links:

http://en.wikipedia.org/wiki/Propylene_glycol

http://webbook.nist.gov/cgi/cbook.cgi?ID=C57556&Units=SI&Mask=7

thank you for that answer - mikerho - i will get some of that also