most orchids hate hard water. house plants should generally be less sensitive to it.
one thing you may want to keep your eye on though, is the ph.

where i live, water coming out of the tap is ph 8.2. plants cant absorb most nutrients at that alkalinity. theyre happier around 6. a couple drops of vinegar, or your feritilizer (if its as acidic as mine) will generally bring it down to where they want it.

supposedly canadian peat will soften water too, ive been experimenting with it for awhile though and havent been able to seriously impact my water hardness. i think i may just settle for a bottled water delivery service.

RO units are easy to install. If you're worried about the daunting task of installing one, they make "tabletop" units that do all the RO on your table or countertop and you can disconnect them from your tap when you don't need to continue producing more RO water.

Sam

Can you give me any more info on the tabletop unit? A link maybe? Thanks.

Rule number one with terrariums is NEVER use tap water. It is absolutely correct that the minerals and salts will build up, and there is no way to get rid of them other than removing all the old new and starting over. I really don't know why you think buying RO water is such a hassle! Get the massive 18 L (5 gallon?) jug, and it should last you for a month, depending on how big your terr is and whether it is sealed or if you open it occasionally. I go through one of those jugs every month in my 85 gal. terr, and that's because I have a misting system which I allow to raise the water level, and then I remove the excess to water my other houseplants. If I just hand misted, It takes much longer to go through a jug that size. Every RO unit I have seen is way more trouble and expense than it's worth. Honestly, it would be a lot more work than buying some from the store every month. They work very slowly, have expensive filters that need replacing fairly often, and the smaller they are, the less water they can do in one shot. So you'd have to remember to do it in advance of when you need it, and then half of the water is waste water, since it's super-concentrated with the minerals that were removed from the other half of the water. You can't use this water to water houseplants, because it would be just too many minerals for them. And in the winter, your outside plants don't need much water. I guess you could use it for washing dishes or something, but you'd have to heat it up first. I really can't see collecting rainwater being a big hassle, either. As long as your downspouts are directed into it, it will naturally fill up with rainwater every time it rains. You could also keep it uncovered in the winter, since mosquitoes breeding aren't really a concern now, not even in Georgia. =) You don't actually have to go outside with a bucket every time it rains. =)

Peat will soften water (not just Canadian peat), but it doesn't really remove minerals, it just changes the pH. Granted, more acidic water cannot hold as many minerals, but if you're softening your tap water in a bucket or something, the minerals have nowhere to go, as they can't evaporate out. I suppose they might precipitate out if you got the pH low enough, but they would still be there in the water, just settled on the bottom of the bucket.

The terrarium is three hundred gallons, so including false bottom and sump and misting system that's probably about 20 gallons of water. What would be more expensive, buying water from the store or using RO? Also I have a 55 gal planted aquarium and 18 other cages. So I guess if I bought and RO system it would also go toward that too...

WOW! That's a big terrarium, never seen one that big!
Could you post some pictures? would love to see it!
Ana :)

Take a look at my posting under Orchid Forum "Rainwater vs tapwater", dated today. I followed advice of a botonist who said to use rainwater for healthy/happy house plants. In their natural environment all plants survive on rainwater and the nutrients it contains. An orchid living high in a tree gets no other fertilization and they seem to thrive. Natures way!

Dick

I know that rainwater is good for watering the plants...I don't know maybe I'm just too lazy to collect it. For now I'll just buy water from the store. BTW rainwater doesn't contain "nutrients" in its pure form - of cousre it does pick up nutrients once it runs through the soil.

This is just a thought, but could you add treatments such as Stresscoat mixed in with your tap water that you use for your aquarium to eliminate chlor and other chemicals that are harmful to fish and to sensitive plants? I too buy water from the store but if I don't have it on hand I treat the water hoping this will help. It keeps the fish alive and so far the plants are not complaining/wilting.
Theresa

I wouldn't recommend Stresscoat, because whatever is in it that promotes the slime coating (I think it's aloe vera gel) on fish will also build up in your terrarium. Sea Chem makes the best dechlorinator. It's called Prime, and it will remove the harmful chemicals. Trouble is, it can't remove the minerals (salts) that mean trouble for terrariums. It's fine for houseplants though. In your case, Cdfortin, it probably would be wise to get an RO unit, since you have SO MANY tanks! (Post pics!!!!). Don't get a small one though, get a bigger one, because it sounds like you'll need it. Really though, it would be more work than collecting rainwater, and a lot more expensive, so I would reconsider your 'laziness'. =)

To sahoy: yes I will post pics under the heading "Brainstorming on a Giant Orchidarium...continued" in about two weeks-by then I'll be back from vactation (to find out where I'm going see my new post).

I disagree about the never using tap water. In Australia most tapwater is pH neutral and soft (even in adelaide with their new plant), due to using rainforest catchments. I think people should test their water for suitability before running off to buy an expensive RO unit.

Now if your tapwater is bore water in limestone country, then sure, it's going to be a problem, but lets not assume that all tap water is bore water or stored in calciferous basins.

On the contrary, minerals are good for the plants. That's what fertilizer is, Nitrogen, Phosphorous, Potassium, Calcium, Magnesium, etc. Too much minerals, however, can be a bad thing. The Total Dissolved Solids (TDS) in the water, together with added fertilizer, can be too much for some plants. You may have to call your water company or have your well water checked for how much TDS is in it. My water has around 220, and with added fertilizer would shoot over 400, much too high for the plants. I use 50% tap water and 50% purified water (from the store) or 50% rain water (which I collect and put into gallon jugs). This lowers the TDS and the plants seem to be doing well on it.

How about distilled water?