RODI Water Setup Guide for Aquariums: TDS, Membranes and Brisbane Tap Water

Brisbane and South East QLD tap water runs through a lot of pipe and picks up chlorine, chloramine and dissolved minerals along the way. Fine for a shower, not fine for coral or shrimp. If you have ever dosed a reef tank with straight tap water and watched alkalinity swing or algae bloom for no obvious reason, the water itself was probably the problem. An RODI unit fixes that at the source, and this guide walks through picking one, installing it, and knowing when the membrane or resin needs changing.

Contents

• What RODI actually does
• What does TDS mean for an aquarium
• Choosing an RO unit for Australian tap water
• Comparison: sediment vs carbon vs membrane vs DI
• Installing and running the system
• Membrane and resin swap schedule
• Good, Better, Best setups
• FAQ

What RODI actually does

RODI stands for reverse osmosis, deionisation. The RO stage pushes tap water through a semi permeable membrane under pressure, stripping out the bulk of dissolved solids, chlorine, chloramine and heavy metals. What comes out the other side is called permeate, and it is already very clean. The DI stage is a polishing step. Water passes through resin that grabs the last trace of dissolved minerals, taking TDS down close to zero.

For a reef tank, this matters because tap water phosphate, nitrate, silicate and copper feed algae and stress corals long before you notice a problem on a test kit. For freshwater and shrimp tanks, unpredictable tap water hardness makes dosing and breeding far harder to get consistent.

What does TDS mean for an aquarium

TDS stands for total dissolved solids, measured in parts per million (ppm). It is not a single contaminant, it is a rough measure of everything dissolved in the water, minerals, salts, metals, organics. Brisbane tap water typically sits somewhere between 40 and 120 ppm TDS depending on the suburb and time of year, sometimes higher after heavy rain events affect the catchment.

For reef tanks and RODI water used for coral, the target is 0 ppm TDS, or as close to it as your gear allows. Anything above 1 to 2 ppm before it reaches your mixing vessel means either the membrane is due for replacement or the DI resin is exhausted. A TDS meter should sit inline after the membrane and again after the DI resin so you know exactly where a rise starts. The TDS meter range covers both handheld and permanent inline options for this.

Choosing an RO unit for Australian tap water

Two things decide which unit you need: how much water you use per week and how hard your local tap water is. A frag tank or small reef doing a 20 litre water change weekly is a very different job to a 500 litre display needing 100 litres of top up water a week plus change water.

GPD (gallons per day) ratings on RO units describe membrane output under ideal pressure and temperature, not a guaranteed daily figure in a Brisbane laundry with mains pressure that varies by suburb. As a rough rule, halve the rated GPD figure to estimate realistic daily output at home, and buy a bit bigger than you think you need.

Comparison: sediment vs carbon vs membrane vs DI stage

Installing and running the system

Most Australian homes run an RODI unit off a laundry tap or a dedicated saddle valve tapped into the cold mains line, feeding into a bucket, drum or purpose built reservoir. A few basics make the difference between a smooth setup and a wet floor.

• Fit the sediment filter first in the line, then carbon block, then membrane, then DI resin, in that order. Reversing this shortens membrane life fast.
• Run the first 10 to 15 minutes of new membrane output to drain before collecting it, since new membranes shed a bit of preservative.
• Use flexible push fit tubing rated for RO systems, and keep waste water (concentrate) running to a drain or garden, since a membrane typically produces 3 to 4 parts waste to 1 part clean permeate.
• Check pressure. Mains pressure below around 40 psi will starve the membrane and drop output noticeably, a small booster pump fixes this in older Queenslander homes with weaker plumbing.

Plumbing fittings, quick connectors and spare tubing sit in the plumbing collection if you need to extend a run out to a fish room or garage.

Membrane and resin swap schedule

Sediment and carbon stages are cheap and should be swapped on a calendar, not just when they look dirty, since carbon exhaustion is invisible until chlorine starts hitting the membrane. Every 6 months is a safe default for typical Brisbane household use.

The membrane itself usually lasts 12 to 24 months depending on tap water quality and how much volume passes through it. Watch output volume drop and TDS creep up as early signs. DI resin is the easiest to monitor because colour changing resin (like the Reef Pure Color Changing DI Resin or the resin used in the Reef Pure Single DI Resin Cartridge) visibly shifts colour from the inlet end as it exhausts, giving a clear visual cue well before your TDS meter confirms it.

Good, Better, Best setups

Good: small reef or planted tank, under 30 litres water change weekly

Reef Pure RO 4 Stage 50GPD Essentials+, $356, paired with an AutoAqua Digital Inline TDS Titanium meter, $59, to keep an eye on output quality without needing a separate handheld unit.

Better: medium reef, 50 to 100 litres weekly

Reef Pure RO 4 Stage 100GPD Premium, $446, with a Reef Pure Dual TDS Meter, $60, monitoring both pre and post DI readings simultaneously so you catch membrane fade before resin exhausts too.

Best: larger systems or shared fish room supply

Reef Pure RO 4 Stage 100GPD Premium unit run into a dedicated reservoir, backed by a spare Reef Pure Single DI Resin Cartridge, $113, on hand for immediate swap, plus Triton DI Resin, $35, as a rotating spare so there is never a day without clean water on tap. Browse the full RODI collection and Reef Pure systems to configure your own stack.

FAQ

What TDS should my RODI water read for a reef tank?

0 ppm is the target straight after the DI stage. Most hobbyists get comfortable seeing anything up to 1 ppm, but a steady climb past that means it is time to check resin or membrane condition.

Anything measurable in the water going into your mixing container should be treated as a warning sign, not background noise.

Can I use tap water for a reef tank if I dose extra minerals?

Not reliably. Tap water carries phosphate, nitrate, silicate and sometimes copper that no amount of calcium or magnesium dosing can remove. Products like Triton Magnesium Increaser 4kg, $70, are for adjusting clean RODI or saltwater parameters, not for masking tap water contamination.

How often should I replace the RO membrane?

Typically 12 to 24 months for average Brisbane household use, sooner if output volume drops noticeably or TDS readings after the membrane start rising above a few ppm.

Do I need a TDS meter if I already have colour changing DI resin?

Colour changing resin gives a visual heads up, but a proper meter gives you an actual number and catches issues before the colour shift is obvious. Running both, like the Reef Pure Dual TDS Meter alongside colour changing resin, is the most reliable combination.

What is the difference between an RO unit and a full RODI unit?

An RO only unit stops after the membrane stage and will still leave a few ppm TDS in the water. Adding the DI stage after the membrane polishes that remaining TDS down to effectively zero, which is what reef tanks and sensitive freshwater setups need.

Prices are accurate at the time of publishing and are subject to change. Check the product page for the current price before buying.