RO/DI with Phosphates but 0 TDS

[seabass]

Yes, that's a good article (already had it bookmarked). It explains that daily top offs, with water containing 0.05ppm of phosphate, makes little difference compared to feeding a tank (and I would agree with that). This is the same thing that our OP has experienced.

 

What it doesn't explain is that you use this same water to make saltwater. So instead of starting with phosphate at 0.00ppm, it would start at 0.05ppm (and go up from there). Then, I assume, you use expensive GFO to reduce it, and possibly precipitate out some alkalinity (making dosing necessary).

 

Water changes would actually serve to increase phosphate levels (kind of ironic since typical advice to reduce algae often includes increasing the volume and/or frequency of water changes). But it's still an interesting article; I'll have to reread it when I have some more time.