Gear Score Methodology
PetPal Gear Score
Best RO/DI Water Systems for Reef Aquariums (2026)
Editorial synthesis of manufacturer specifications (Bulk Reef Supply, AquaFX, LiquaGen, AquaticLife) and reef-keeping education from Bulk Reef Supply — no first-hand product testing. The Pure Water Score is a composite of published specs and expert/hobbyist consensus, not a measurement. PetPalHQ does not run a testing lab. Ranks reflect each pick's best-fit use case — form factor, output, and budget — rather than raw score order, and the score rates purification capability, build quality, capacity, and serviceability within a pick's class. Value is one explicitly weighted factor of the score; it is the smallest weight, so a higher rank never means a higher score.
Pure Water Score = (Purification Performance × 0.35) + (Build Quality & Components × 0.25) + (Production Capacity × 0.20) + (Maintenance & Serviceability × 0.12) + (Value × 0.08)Factor breakdown
Purification Performance
35%How thoroughly the system strips contaminants and polishes water toward 0 TDS, based on the membrane and the deionization stage. We synthesize this from manufacturer specs on the RO membrane and DI resin and from Bulk Reef Supply's framing that the DI stage is what brings RO water down to 0 TDS for a clean reef base. The Pure Water Score is a composite of published specs and expert consensus, not a measurement — PetPalHQ does not run a testing lab.
Build Quality & Components
25%Quality and serviceability of the housings, bracket, fittings, and instrumentation. We credit included monitoring (inline TDS meters, glycerin pressure gauges), durable brackets, USA-made membranes where documented, and standard versus proprietary cartridge formats.
Production Capacity
20%Rated gallons-per-day output relative to a tank's likely top-off and salt-mix demand. GPD is a production rate that depends on feed pressure and water temperature, so we treat a unit's rated figure as a ceiling and weight it against realistic demand rather than rewarding the biggest number outright.
Maintenance & Serviceability
12%How easy the system is to live with — cartridge changes, flush kits, dual-DI capacity, and visual exhaustion cues like color-changing resin. We reward designs that make membrane and resin changes painless, since the most common owner failure is leaving spent media in too long.
Value
8%Purchase price relative to capability and the longer-run cost of replacement membranes and resin. This is the smallest weight in the score by design, so a strong-value pick never outranks a better-purifying system on the score alone — value breaks ties, it does not drive the ranking.
See all score methodologies on the Gear Score index.