In the aquarium hobby, everything starts with water. It's often said that we shouldn't think of ourselves as reef keepers, but rather water keepers.

Tap water often contains chlorine, unwanted nutrients, and other contaminants that can cause problems fast. An RO/DI system removes the guesswork and gives you consistent, zero TDS water to build from.

If you're new to the hobby and RO/DI systems, you might be asking yourself: Which RO/DI system is the best?

How to Choose the Right RO/DI System

Choosing the right RO/DI system comes down to a few simple factors:

  • Souce water quality
  • How much water you need
  • How fast you want the water
  • How efficient you want your RO/DI system to be

Step 1: Choose Your Filtration Level (Number of Stages)

GOOD: 4 Stage Systems

4 Stage RO/DI System with Filter Stages Labeled

Ideal for: Filtering city water treated with low levels of chlorine or well water with low levels of contaminants.

Other Benefits of a 4 Stage RO/DI System:

  • Most affordable options in our RO/DI lineup
  • All filtration stages are contained to a single bracket, making these systems the most portable

BETTER: 5 Stage Systems (Most Popular)

5 Stage RO/DI System with Filter Stages Labeled

The BRS 5 Stage RO/DI systems are our best selling systems. They are a good balance of price and performance as they are our least expensive systems that can handle chloramines commonly found in city water sources.

Ideal for: Filtering city water treated with chlorine or chloramines, plus well water sources near industrial or agricultural areas.

Other Benefits of a 5 Stage RO/DI System:

  • Second carbon block adds protection against chloramines

BEST: 6 Stage Systems

6 Stage RO/DI System with Filter Stages Labeled

Ideal for: Filtering city water treated with chlorine or chloramines, plus well water sources near industrial or agricultural areas.

Other Benefits of a 6 Stage RO/DI System:

  • Second carbon block adds protection against chloramines
  • Second mixed bed DI stage
    • Allows for longer time between DI canister swaps
    • Allows for first in, first out DI swaps to ensure product water is always 0 TDS

BEST OF THE BEST: 7 Stage Systems

7 Stage RO/DI System with Filter Stages Labeled

Ideal for: Nearly any water source. Filters city water treated with chlorine or chloramines, plus well water sources near industrial or agricultural areas. Also ideal for source water with high concentrations of dissolved CO2.

Other Benefits of a 7 Stage RO/DI System:

  • Second carbon block adds protection against chloramines
  • Triple DI stages allow for separated cation, anion, and mixed bed resins
    • Separate resins mean changing only the resin type that is exhausted, resulting in wasting less DI resin
    • Ideal setup for challenging water supply conditions like high CO2 concentration that exhausts anion resin quickly

Step 2: Configure Your System

Once you've identified how many stages you need, there are just three more details to narrow it down.

1) Single Membrane or Dual Membrane Water Saver Setup?

Standard Single Membrane Systems

Pros:

  • Simple
  • Less Expensive
  • Ideal for High TDS Source Water (300+ TDS)

Cons:

  • Higher Waste to Product Water Ratio (approx. 3:1)
  • Slower Water Production Speed
  • Fewer Gallons Produced Per Day

Dual Membrane Water Saver Systems

Pros:

  • Faster Water Production
  • More Gallons Produced Per Day
  • Lower Waste to Product Water Ratio (approx. 1.5:1)
  • Ideal for High TDS Source Water (300+ TDS)

Cons:

  • Slightly More Complex
  • Slightly More Expensive
  • Not Ideal for High Source Water TDS (300+)

2) Standard or Plus Model?

Most of our systems are offered in a standard or "Plus" model. Plus models give you everything the standard models have but with three helpful features pre-installed.

Plus Models Include:

  • Glycerin Filled Pressure Gauge
    Lets you monitor incoming water pressure, which is critical for RO membrane performance.
  • Manual Flush Valve Flow Restrictor
    Allows you to flush the system before and after use, helping to extend the life of the RO membrane.
  • Inline TDS Meter
    Gives you insight into the TDS after the RO membrane as well as the TDS of your final product water.

3) Membrane Size - How Many Gallons Per Day?

Most of our systems are offered in the following configurations:

  • Single Membrane: 75 or 100GPD
  • Water Saver: Dual 75 or dual 100GPD (150 or 200GPD total daily water production, respectively)

Note: Incoming water pressure greatly affects actual water production rate. If your water pressure is less than 50PSI, expect fewer gallons per day. If your water pressure is higher, you may actually produce more water than advertised.

Optional: Booster Pump

As noted above, low water pressure can result in poor RO membrane performance. This can lead to slower water production, a decreased rejection rate, and faster DI resin use.

If your water pressure is below 50 PSI, consider adding a booster pump to improve performance and efficiency.

Learn More: How to Install a Booster Pump on an RO/DI System