olá,
não sei a quantidade necessária de água para as TPA's senão podias tentar numa fonte ai da tua zona de certeza que trazia níveis mais baixos...
já agora o tal produto, Purigen da Seachem, segundo eles é para retirar nitratos, nitritos, amónia entre outros...
"Seachem Purigen 100 ml bagged
Purigen is a premium synthetic adsorbent that is unlike any other filtration product. A 100 mL bag of Purigen purifies and polishes up to 100 gallons of water for up to six months
It is not a mixture of ion exchangers or adsorbents, but a unique macro-porous synthetic polymer that removes soluble and insoluble impurities from water at a rate and capacity that exceeds all others, even HyperSorb™, by over 500%. Purigen™ removes proteins, nitrites and nitrates, ammonia, and a broad spectrum of organics, yet its impact on trace elements is minimal. It significantly raises redox. It polishes water to unparalleled clarity. Like HyperSorb™, Purigen™ darkens progressively as it exhausts, and is easily renewed by treating with household bleach. A 100 mL bag of Purigen™ purifies and polishes up to 100 gallons of water for up to six months. Purigen™ is designed for both marine and freshwater use.
DIRECTIONS: Rinse before use. Use in a fine mesh filter bag. Each 250 mL treats up to 250 gallons for up to six months. Exhaustion is indicated by a pronounced discoloration of the beads to dark brown or black."
mas eu não tenho comissão da Seachem (lol) se tu usares... eu vou experimentar e achei que podia ser uma ajuda para ti também e como não é muito caro...