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My system has been up and running for a couple months and recently I started noticing a white powder residue substance on some of my Hydroton (you can see it on the attached picture). It is a indoor system and under a 600 watt LED.  My first thought was mildew but I have none growing on any of my plants. I read somewhere that it might also be efflorescence caused by salts and minerals during evaporation? Any thoughts or experiences with this??? 


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I used to get salts all the time in hydro applications.  I don't want to wager a guess based on the one picture.  Can you get a nice macro shot?

Attached are two more close up shots. From all the research that I've done, it seems to be what is referred to as "efflorescence" (salt and minerals deposits that build up during evaporation). 

matthew ferrell said:

I used to get salts all the time in hydro applications.  I don't want to wager a guess based on the one picture.  Can you get a nice macro shot?


have you salted your system? or used any additives? (ph up or ph down or any of those? )

i'd put my money on salt.. give it a taste

Benjamin, even if you didn't add any extra salts, the problem could be from your tap water to begin with.  The mineral and salt content of tap waters all over the country are all over the map, but having relatively low mineral/TDS(total dissolved solids) water is rare in the western half of the US.  This isn't just pH.  Most municipalities, even in the eastern US, where their source waters are potentially soft, run their water over Limestone in increase the Calcium hardness and pH, while the overall TDS could still be fairly low, and you'd still call the water "soft", ie easily acidified.  The reason they do this is that having extra Ca ions in the water tends to keep the lead in solder plumbing joints in older homes from moving into the tap water.  All homes built after the mid-80's had lead free tin based solder.  I think most of the tap waters in California tend to be fairly high in sodium plus lots of other minerals too.  Certainly the worst would be Colorado river water, which is nasty, but even water from the central valley and even the eastern Sierria(Mono Lake) are potentially pretty high in salt.  When we lived in Diamond Bar, SoCal, I got a RO for both me and my Orchids.  Now we live in the Dallas Area, and due a lucky bit of geography, the DFW and surrounding areas have fabulous surface water quality.  The large rivers that flow out of West Texas and New Mexico, and are nasty salty, don't flow through the DFW metroplex.  All our water comes from the Trinity watershed basin, which is all located here in the relatively wet North Central Texas(about 36 inches or rain per year).  Tap waters for people who use the Red River north of us and the Colorado, etc rivers south of us(Waco, Austin, etc) are nasty salty.  The Trinity river eventually flows down to Houston, so they are lucky too, although they get mostly our toilet flushings,(sorry Houstonites).  Even though most of the soils around here are alkaline and limestoney, this just makes the calcium hardness high, but overall our water is pretty soft.

I don't know if there is anything practical for you to do, as it would be expensive to get enough RO filters to supply your whole system.  Plus it may not be necessary.  The fish love salty mineral rich water, and as long as the salts don't built up, the plants probably can handle it.  I don't think plants hate sodium so much as they hate chlorides.  If you are adding any extra fertilizers, avoid those where the potassium comes from potassium chloride(aka muriate of potash), which are generally the cheaper fertilizers.  Potassium sulphate, or Potassium magnesium sulphate(sul-po-mag) are in the better higher quality fertilizers.  "We have the best Potassium" - Borat.

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