Aquarium gear checklist

A calculator is only as good as the numbers you feed it. This is the short list of gear that makes those numbers trustworthy, and what separates a good one from a bad one.

Setting up a tank

• Tape measure (metric and imperial)
  A 5 m / 16 ft tape with both scales, so you can read inside dimensions in either unit.
  Used with: Tank volume & water weight
• Spirit level
  At least 60 cm (24 in) long. Check the stand front to back and side to side, before and after shimming.
  Used with: Tank volume & water weight
• Aquarium stand
  A maker-stated load rating above the full weight (water, glass, substrate and rock), and full support under the tank frame.
  Used with: Tank volume & water weight

Testing water

• Nitrate test kit
  A liquid reagent kit rather than strips, within its expiry date. Test your tap water too.
  Used with: Water change & dilution
• KH test kit
  A drop-count titration kit with 1 dKH resolution, or a digital alkalinity checker for reef tanks.
  Used with: CO₂ from pH & KH, Water change & dilution
• pH meter with calibration buffers
  Two-point calibration (pH 7 and pH 4 buffers), automatic temperature compensation and a replaceable probe.
  Used with: CO₂ from pH & KH
• Digital thermometer
  A probe thermometer accurate to ±0.5 °C (±1 °F) or better. Check it against a second thermometer once.
  Used with: Salinity & specific gravity, Heater wattage

Water changes

• Siphon / water-change hose
  Long enough to reach your sink or drain, with a faucet adapter that fits your tap and a gravel tube sized to the tank.
  Used with: Water change & dilution
• RO/DI unit
  A DI stage for reef use (0 TDS), an inline TDS meter, and a gallons-per-day rating that fits your weekly water needs.
  Used with: Water change & dilution, Salinity & specific gravity

Planted tanks: fertilizer and CO₂

• Digital scale (0.01 g)
  0.01 g resolution, 100–500 g capacity, and a calibration weight in the box.
  Used with: Fertilizer dosing (dry salts)
• Dry fertilizer salts
  Labelled purity and full water solubility for KNO₃, KH₂PO₄ and K₂SO₄, plus a chelated trace mix. Store dry and sealed.
  Used with: Fertilizer dosing (dry salts)
• Graduated dosing bottles
  Clear mL markings, and dark or opaque bottles for iron and trace mixes, which light degrades.
  Used with: Fertilizer dosing (dry salts)
• CO₂ drop checker + 4 dKH reference solution
  Use a 4 dKH reference solution, not tank water. Place it low in the tank, away from the diffuser.
  Used with: CO₂ from pH & KH

Reef tanks: salinity

• Seawater refractometer (ATC)
  A natural-seawater scale (not a brine or salt scale), automatic temperature compensation, and room to calibrate.
  Used with: Salinity & specific gravity
• 35 ppt calibration fluid
  A sealed 35 ppt (53 mS/cm) seawater standard within its date. RO water alone only sets zero.
  Used with: Salinity & specific gravity

Heating

• Adjustable aquarium heater
  A wattage from the calculator, a visible set point, and a shatter-resistant body. Two smaller heaters fail more safely than one big one.
  Used with: Heater wattage
• Temperature controller
  Its own probe, a power rating above your heater wattage, and a cut-off or alarm 1–2 °C above target.
  Used with: Heater wattage

We list what to look for rather than chasing the newest model, and we say when we haven't tested something ourselves. See our affiliate disclosure.