FastAquatics
Side-by-side equipment comparison

RODI vs Tap Water for Aquariums

RODI vs Tap Water for Aquariums side-by-side comparison. Pros, cons, when to pick each, and recommended setups for each tank type.

RODI Water

Pros

  • 0 TDS (no contaminants)
  • Predictable parameters
  • No phosphate (prevents algae)
  • No copper / chloramine
  • Reef-safe + planted-tank-safe

Cons

  • Requires $100-300 RODI unit upfront
  • Wastes 4 gallons per 1 gallon produced
  • Membrane + DI replacements ongoing
  • Slower water-change preparation

Tap Water (Dechlorinated)

Pros

  • Free or cheap (water bill only)
  • No RODI unit needed
  • Always available
  • Fine for hardy freshwater fish
  • Fast water changes

Cons

  • Contains chloramine (kills bio-filter)
  • Phosphate fuels algae
  • May contain copper (kills inverts/coral)
  • TDS varies by season + city
  • Will not work for reef tanks

Which to pick (by use case)

Use caseRecommended
Saltwater / reefRODI (mandatory)
Planted high-techRODI + remineralization
Community freshwaterTap with Prime is fine
Discus / wild apistosRODI + remineralization
Coldwater goldfishTap with Prime

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