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

More equipment comparisons

Browse all side-by-side equipment comparisons. Or use the calculator collection to verify equipment sizing for your tank.

Choosing aquarium equipment that lasts

Equipment is where you allocate budget for stability. The cheapest pump runs hot + dies in 18 months; a quality pump runs cool for 8-10 years. The math on equipment is dramatic: a $400 quality canister filter beats four $100 cheap canisters across a decade, plus saves you the maintenance headaches + livestock losses from failures.

Three principles for equipment selection: 1) Oversize for the job - rated GPH is always inflated by 30-40%; size everything for the worst-case load. 2) Brand-name over no-name - established brands (Eheim, Sicce, EcoTech, Tunze, Hydor, Reef Octopus, Fluval) have parts available + service centers. 3) Plan for redundancy - 2 smaller heaters beat 1 large one (if one sticks, the other still works + the controller catches it).

For purchase planning, use our equipment budget builder, heater wattage calculator, protein skimmer sizing, and filter turnover calculator.

Frequently asked questions

Should I buy used equipment? Yes for tanks + stands + plumbing (inspect for cracks). No for pumps + heaters + UV bulbs (unknown remaining life). Maybe for skimmers if you can clean + verify.

How long should equipment last? Quality heaters: 2-3 years (replace preventively). Pumps: 5-10 years. Skimmers: 10+ years (replace pump every 3-5). Filters: 10+ years (rebuild seals every 3-5). LED fixtures: 5-7 years.

Wattage vs gallons rule for heaters? 3-5W per gallon for cool rooms, 1-3W per gallon for warm rooms. Use 2x smaller heaters for redundancy + safety. See heater wattage calculator.

Sump or HOB filter? HOB for tanks under 40g (cheap, easy). Canister or sump for 40g+ (better filtration capacity, room for media customization). Sump required for 75g+ reef.

What about controllers (Apex, Inkbird)? Inkbird ($30-50) for any tank - protects from heater failure. Apex ($400-800) for SPS reef + dosing automation + Wi-Fi alerts. Worth every penny.

Related resources

All equipment · Best aquarium by size · Equipment comparisons · Brand vs brand · Equipment budget builder · Calculator library (29) · DIY projects · Apex controller glossary