OK, a little schooling is in order.
First off prefilters and carbons have very little to absolutely nothing to do with TDS. Think about it, they are in the 10, 5, 1 or maybe 0.5 micron ranges. Thats suspended solids.
TDS or dissolved solids are in the 0.0001 micron range, many many times smaller than those are capable of removing.
You CANNOT use TDS as a gauge or measure on when to change prefilters and carbons, theye serve two different purposes. TSS (sediment, particulates, colloidal materials, silt etc) is removed by the prefilter and carbon along with chlorine and some VOCs. They are there solely to protect the expensive RO membrane whose job it is to remove 90-98% of the TDS with the DI resin getting the rest.
What you need to understand with TDS is if any is present, its possible you have more than you know. Weakly ionized substances like nitrates, phosphates and silicates are just tha, they contain very weakly chaged ions so do not measure well on a TDS meter. You can have high silicates and phosphates in the treated water and not even know it. Another very very important point is DI resins starte releasing these weakly ionized substances even BEFORE it is exhausted. That means when you start seeing 1 or 2 TDS up for 0 TDS you are starting to release contaminants the DI resin has attracted over time and put it back in the treated RO/DI water. Since they are weakly ionized you may not see them and again they will not test well on a TDS meter or hobbyist grade test kits since it is ultrapure water, but rest assured they are present if they were in the tap water.
You always change prefilters and carbon blocks every 6 bmonths like clockwork. At this same time it is advised you disinfect the system with household bleach following the directions I have posted many times to reduce the chances of virus and bacteria growth. You change the RO membrane when it is no longer cost effective to keep changing DI resins frequently and you change the DI resin when it is anyting other than 0 TDS on a regular basis.
This is what I'm dealing with. I'm seeing it only on the tank back (in pix) all the glass and on the powerheads. I don't know whether it's Dino's or Diatoms. I just scraped the back yesterday~I took this pix today. So it came back overnight.
What you are seeing is normal in unmature systems and the reason why I paint my backgrounds black rather than blue. I don't clean the back and with black you don't see it, with blue like my sons tanks have it looks nasty.
A reef will continue to evolve and go through algae stages for up to a year or more. I remember when I first set up my present system 7.5 years ago, it went through every stage you can imagine before settling down. I have never used anything but RO/DI from a well maintained Spectrapure MaxCap so I know none of it was water quality related yet I still had it all and in every color of the rainbow. I went through hair algae, diatom blooms, dinos, bubble algae, cotton candy algae, red slime, green slime, black slime, you name it I had it at one time or another and chalk it up to the maturation process.
Originally Posted by AZDesertRat
OK, a little schooling is in order.
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