Pick the right protein skimmer by tank size, bioload, and sump dimensions. In-sump vs hang-on, needle-wheel vs cone, and the brands worth paying for.
Reef LED selection by tank size, coral type, and target PAR. Radion vs Hydra vs Kessil vs AI Prime - what each excels at.
Heater wattage by tank size, controller-vs-built-in thermostat, and the brands that don't boil tanks when they fail.
Canister filter selection by tank size, planted vs cichlid setups, and the brands that last 10+ years.
Reverse osmosis + deionization sizing, GPD ratings, membrane brands, and TDS targets for reef and shrimp tanks.
Apex vs Hydros vs Reef Kinetics. Probe accuracy, automation depth, and which controller fits your tank size and budget.
Flow rate by tank size, gyre vs propeller, and the brands that don't fail in saltwater after 18 months.
Optical vs float-switch ATOs, redundancy, and the systems that don't flood floors.
UV wattage by tank size, contact time, and when UV actually works (vs marketing claims).
Optical refractometer vs digital salinity tester. Calibration, accuracy, and the testers reefers actually trust.