Help with incorporating RO/DI

[SDK]

I’m just getting started with orchids and keeping a few Phals. Hoping to expand my collection and have a few quick questions.

I also keep a reef tank and have access to plenty of 0 TDS water from a premium RO/DI unit. My tap water is bad enough that we don’t even drink it. I have a water dispenser for that.

I’m figuring that the 400 TDI magnesium loaded sludge that comes out of my tap is not suitable for any orchids.

Reef salts assume 0 TDI water, but I remember from my Discus keeping days that you need to remineralize pure fresh water a bit, at least for fish.

This brings me to my questions.

Can/should I use pure water for my Phals?

Does the answer change based on genus?

If ii should be re-mineralizing, what are my prepared and/or DIY options?

Any help in this would be appreciated. I am currently using bottled water for them but would like to switch over.

[Dimples]

If you’re using municipal tap water in the US (excluding places experiencing extreme water quality emergencies, like Flint) it’s going to be fine for phals. Someone more knowledgeable can probably tell you if there are any phal. species that need pure water, but hybrids and many species really don’t care. I live in Southern California, aka the land of disgusting tasting, super high mineral content water, and my phals are growing like gangbusters on tap water. I use 1/4-1/5 tap + RO for fertilizing to avoid nutrient tie ups, but tap is just fine for most orchids.

I do use RO on my one zygopetalum because I’ve read that they seem to be much more sensitive to water quality. It still gets the same tap + RO fertilizer mixture and so far it’s growing fine.

[Roberta]

Totally agree with Dimples. If you use super-pure water, you have to then make sure that you add calcium and magnesium into your fertilizer mix (or use a cal-mag fertilizer designed for pure water). Phals don't care. You could mix tap water with pure water to give a source of minerals but reduce the hard-water salts if it makes you feel better. I also don't know about whether there are species phals that need it, but for sure hybrid Phals truly don't care. Save the pure water for the high-elevation Pleurothallids and such, don't stress about it for the hybrid Phals. Just don't use softened water, which replaces the chalky calcium with sodium (tastes batter, horrid for plants) If you have a water softener, get your plant water from an outdoor hose bib, outdoor water doesn't go through water softener systems.

[estación seca]

Phoenix over the years has had 600-1,200 ppm TDS. No problem for Phals.

[Ray]

In my opinion, “can tolerate” and “no problem” is entirely different from “can they benefit from” pure water, and the answer to that is a resounding “yes”. At the very least, plants grown with pure water supplies tend to have mush glossier, healthier-looking leaves. (I also think they get fewer diseases, but there are so many factors that can affect that, it’s probably impossible to be certain without a large, controlled study.)

Orchids have evolved in environments with extremely pure rainwater, so it seems logical that pure water is what their physiologies are designed to deal with.

You will have to supply everything via your fertilizer, including Ca and Mg, as Roberta wisely pointed out, but that does not change by genus. What might change is the amount of nutrition needed, but that’s related to growth-rate, not an inherent difference in the needed ions.

That said, it is not necessary to add fertilizer to the water at every watering, just be sure to do so regularly.

[SDK]

Thank you all for the helpful replies. I am most likely going to go with the pure water and added ferts and see how things progress.

To further clarify my earlier posts. I already own a good RODI unit and am making 5 to 10 gallons per week for the reef tank. There is almost no extra effort and a cost of maybe 25 cents per month to divert an extra gallon or two over to the plants. Even a small benefit should outweigh the negligible cost.

I will start looking at some fertilizer options and understand to go light with the additives. Especially at this time of year.

[tmoney]

and much better (perhaps) environmentally than using bottled water each week.

[SDK]

Originally Posted by tmoney

and much better (perhaps) environmentally than using bottled water each week.

I 100% agree with that. I was using water from the water cooler in my kitchen that has the 5-gallon returnable bottles. I do everything I can to avoid single use plastics.

The thing is, once you already have the equipment, RODI is literally pennies per gallon if you are not living in an area with abnormally high water bills. If it's also possibly better for the plants, it's a win/win in my particular situation...

[tmoney]

ah, gotcha...hey culligan man!!



oh the things we used to do with those jugs back in the day....memories, memories....

[estación seca]

Reverse osmosis units waste up to 80% of water input. It goes down the drain. It's the reason I decided to collect rain.