Phosphates or Silicates slipping past TDS meter?

[jostafew]

Hey everyone, I've got a question re. TDI and phosphates / silicates, but first a little background: Ever since I moved from Langley to Abbotsford my tanks have gone to crap with cyano and red/brown algae everywhere (one moved, the other one in the my work office was undisturbed). Everything is the same except for the source water. TDS meter showed reading on source water of about 15-20ppm in Langley which went to 25-120ppm in Abby, water tasted kinda funky too. TDS leaving the RODI went from 0 to 1-2 after moving. Ran this for a while and noticed the problem appearing. Been about 8 months of this.

Ok, changed the first three stages (mechanical and carbon), and DI stage of the filter, TDS on the output side now down to 0 again. Ran that for a couple months, no change (algae that I physically removed had all regrown).

Started running rowaphos in a reactor and another water change, junk grew back just as fiercly...

Down to the question in the subject, will problematic phosphates and/or silicates show up as TDS for my meter to detect or is it possible that junk is slipping through because I didn't change the RO stage of the filter (didn't change because TDS now reading 0ppm)? I'd like some feedback before I throw money at a full set of filter elements.

Thanks in advance

[Torx]

TDS is PPM. 0 tds on your meter does not mean 0.00 ppm. Just means that it is less then 1.00 ppm. So yes, problematic disolved solids such as phosphates could still be in the water. Plus the time water sits will increase as well.

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[denny_C]

although unless your tank is tiny the small amount of phosphates you add is but a blip on the radar when compared to other po4 sources.

[hillegom]

Test your water after the ro part and before the DI. The DI reduces the TDS to 0 until it is exhausted. You don't need any other filters to do that. Problem is DI costs a lot so u only use it to give the water a final polish.
Your RO filter should bring your water to at least 98% TDS free.(actually varies, depending on the gpd figure of your ro) If you start with 25ppm it should read 0 after the ro.
Your prefilters will take out the particulates first, then some dissolved solids.
Your TDS meter will only read dissolved solids, not particulates. I do not believe any dissolved solids will "sneak" past the meters ability to read them.

[hillegom]

I agree with the above, both posts.
Depends on your meters ability, how accurate it is.
However, the DI will take out the ppt until it is exhausted.

[StirCrazy]

no they will not register on the TDS meter.

Steve

[jostafew]

You're right Torx, 0 indicated TDS does not = 0ppm

Denny, I'm assuming that you're saying the amount of Phosphate that might be getting through is a small amount compared to other sources... Such as overfeeding & fish poop I'm assuming? My main system is 50gal total volume, in a 35gal shallow reef display with open top. I put about 5gal of makeup water through it a week. Office tank is 8gal nano, with solid lid, maybe 1 gal a month? Both are what I would consider lightly stocked.

Stircrazy, thanks for confirming

[reefwars]

Originally Posted by jostafew

You're right Torx, 0 indicated TDS does not = 0ppm

Denny, I'm assuming that you're saying the amount of Phosphate that might be getting through is a small amount compared to other sources... Such as overfeeding & fish poop I'm assuming? My main system is 50gal total volume, in a 35gal shallow reef display with open top. I put about 5gal of makeup water through it a week. Office tank is 8gal nano, with solid lid, maybe 1 gal a month? Both are what I would consider lightly stocked.

Stircrazy, thanks for confirming

Yes would be very small in comparison . Since this has been a long battle for you what have you ruled out so far? As far as a cause of cyano really there could be many. Are corals suffering?