Safe RO Water Storage

[MateoinLosAngeles]

Hey all,

I've been dealing with some rot issues for the past few days, they all happened in plants that were in S/H and that had a foul-fermented smell coming out of the pots. My plants in bark or sphagnum didn't have any distinctive foul smell. I decided to water the plants with chlorinated tap water, and the smell went away immediately. Three plants I've had to treat through other means.

Then, I saw in my fertilizer concentrate, which I make myself using the same RO water I use to water the plants, what seemed like white spores floating in the concentrate with mycelium-like filaments.

I probably will not go through the identification of these spores since it will probably be easier to make new fertilizer, but since this rot issue happened only on S/H plants, I started to wonder if I've been using contaminated water. This is also something of concern for me since I use the same RO water with my humidifiers.

The RO membrane should be able to remove most microorganisms. However, it might take really little to contaminate a batch over time, especially if one leaves the storage tanks open. I store my RO water in jugs. Or maybe there could've been a blip in the concentration of "water molds" on any given day. Maybe the RO membrane (4 months old) is in need of cleaning...

I don't like to use chlorinated water because I supplement it with live microbes. I use Quantum Total from Ray about twice a month, and I do a drench with Bacillus amyloliquefaciens and Bacillus subtilis concentrates from Arbico Organics about once a season.

So my question is... What do we know about safely storing and using RO water? This water is mostly chlorine free since the membrane is able to get rid of it, which does make it vulnerable to microorganisms.

Assuming this might've been an issue with Phytophthora, I could gather some information:

• - Some nurseries lower the pH of their irrigation water below 4, which has shown to be effective against Phytophthora. Most orchids should be able to take this. Not sure how Paphs, some terrestrials, or even Oncidiums would respond, though.
  
• - Another source mentions pH below 3 seems to kill Phytophthora completely.
  
• - Heat above 140ºF also kills Phytophtora.
  
• - Using bark might help, especially if it's been composted, since it favors the growth of antagonistic fungi like Trichoderma sp., however, it would mean giving up on the many benefits and conveniences of S/H.
  
• - Bacillus amyloliquefaciens, subtilis, licheniformis, megaterium have shown Phytophtora antagonisms, of which B. subtilis 30B-B6 has been singled out as the best.

So some speculative solutions:

• - Could lowering the pH of irrigation water help prevent the spread of Phytophthora? How would this affect calcareous-loving plants like Paphs, Terrestrials, or Oncidiums?
  
• - Could supplementing with beneficial microbes help? The issue here is how to guarantee that the microbes are alive, that the water pH is not too acidic, the concentration and frequency are right, and that the strains are the correct ones. I supplement with microbes, but whatever has caused the problem seemed to not respond to the specific strains that I use.
  
• - For a fertilizer concentrate or for water in a humidifier, could it help to acidify the water below 3 by adding a compound like citric acid? At a density of 1.66 g/cm3, a 5% solution would require adding about 114 g per gallon, but could it deposit or damage a humidifier?
  
• - Could using UV light help?
  
• - Could adding some other bacterial growth inhibitor to the stored water help? And if so, how to make sure that it is not damaging the beneficial bacteria colonizing the plant?