Arka myAQUA 400 Resin Filter for the Arka myAQUA 400 Reverse Osmosis System. The Arka myAQUA 400 resin filter safely and effectively removes even the finest residues of silicate, nitrate and many other dissolved organic and inorganic substances (TDS) and is ideal as an extension to the ARKA myAQUA 400 (used instead of the C2 carbon filter). The Arka myAQUA 400 resin filter contains cationic and anionic resin (H+ and OH- in a 1:1 ratio) and enables the production of pure water with an average conductivity of 0.1S/cm.