I think so. I use the home depot buckets and I test my water coming out of the RODI line and its 0 TDS and 0 phosphates but if I let the water sit in the bucket overnight with a powerhead and a lid on then the water reads .25ppm phosphates. its annoying.
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55 gallon acrylic tank, 29 gallon high sump- 4x54w t5ho 2xUVL superactinics 2x 75/25 UVLs, 75+lbs liverock 100+lbs sand, 2 Koralia #2s
Turboflotor 1000 blue skimmer, Mag 9.5 Return, 800gph overflow
Livestock: Clowns x ii, Hippo Tang, Algae Blenny, Mandarin Goby, CUC.
Corals: 4 types of zoas, 2 palys, 2 clove polyps,GSPs, candy cane, hammer | 
