In Week #7 of our 52 Weeks of Reefing series it is time to add water to the #BRS160 reef tank and we show you guys the best practices for accomplishing this at home and share everything you need to know about RO/DI Systems.

One of the wisest things we have ever heard in this hobby is successful reef keeping has very little to do with maintaining corals and fish and everything to do with maintaining water. Maintaining pristine water with the right parameters simply results in a healthy, thriving reef tank.

Tap water faucet

The importance of clean freshwater

The first step to achieving pristine and stable water chemistry in your reef tank is a reliable water source. For most, it will be your home’s tap water which is likely either untreated well-water or water provided by your city that will contain some type of disinfectant.

Hikari Cloram-X

If the tap water is clean and free of contaminants that would harm the aquarium, you can use either of these freshwater sources for a reef tank without further tap water purification. Clean well-water can be used straight from the tap and treated city water just needs a water conditioner that will neutralize the disinfectant, something like this Chloram-X from Hikari.

Keeping a thriving saltwater aquarium using water directly from your tap, however, is a pipe dream at best.

The issue with this approach is none of us know for sure what’s in our water and even fewer even know what to look for. If you have well water you probably paid for a professional water report at some point to ensure the water was safe for use in your household which would be a great start. You could also contact your city’s water supply and ask them for a water report.

Water Quality Report

The biggest things you would want to look for are heavy metals, phosphate, nitrate, nitrite, disinfection by-products, and uniquely high organic and inorganic chemicals. Even after viewing these reports, some level of uncertainty exists because that was a sample, not the exact water coming from your faucet and going into your tank. Furthermore, it is difficult to be certain how the varying levels of impurities will affect your tank

Ryan replacing RO/DI filters

Dealing with this uncertainty and the hassle of sifting through water quality reports is a chore.

Instead, aquarists purify and produce filtered water at home that is safe for use in aquariums using a Reverse Osmosis Deionization System commonly referred to as a RO/DI system.

Waterboy Meme

Reverse Osmosis Systems - How they work

RO/DI systems contain a series of filters that progressively polish you tap water and essentially remove everything giving you 99.9% pure H20.

Every RO/DI system contains 4 basic stages. Additional stages and filters are added to accommodate a variety of water quality conditions and production demands.

RO/DI System Filter Stages

Sediment Filter - The first stage that is a tightly woven mechanical filter typically made of polypropylene, polyester or cotton fibers. This is your first line of defense that physically filters out rust, dirt and various sediment particles much like a filter sock or filter pad in your aquarium.

Carbon Block - The second stage containing carbon that reduces disinfectants and chemicals via adsorption. This is a very important component because it is where chlorine and chloramines will be removed. Choosing the correct carbon filter for your source water (Chlorine vs Chloramines) is important for optimal filter life span.

RO Membrane - The powerhouse and heart of your RO/DI system that removes a majority of the salts, metals and other contaminants via semipermeable membranes. It is made of thin layers of special materials that separate the impurities and creates two channels of water. The reject (waste water) carries the contaminates and permeate (product water) that is clean and free of impurities.

DI Cartridge - The deionization stage is the final filter the water passes through that is filled with ion-exchange resins that polish the water and remove virtually everything the RO membrane missed to produce “DI water”. These will be things such as nitrate, nitrite, phosphate and residual chloramines which have low molecular weights or small ionic charges making it difficult for the membrane to remove them.

BRS RO/DI 4 Stage Value Plus RO/DI System Comparison

  4 Stage 75 GPD Value Plus RO/DI System 4 Stage 75 GPD Value Plus RO/DI System 4 Stage 150 GPD Value Plus RO/DI System 4 Stage 200 GPD Value Plus RO/DI System
Gallons Per Day
Sediment Filter
Purtrex 5 Micron Depth Sediment Filter 
Purtrex 5 Micron Depth Sediment Filter 
Purtrex 5 Micron Depth Sediment Filter 
Purtrex 5 Micron Depth Sediment Filter 
Carbon Block
BRS VOC 5 Micron Carbon Block 
BRS VOC 5 Micron Carbon Block  
BRS VOC 5 Micron Carbon Block
BRS VOC 5 Micron Carbon Block
75 GPD Dow Filmtec Membrane*

100 GPD Dow Filmtec Membrane**

Dual 75 GPD Dow Filmtec Membrane*

Dual 100 GPD Dow Filmtec Membrane**

Deionization Resin
Single Mixed Bed DI Stage with Refillable Cartridge

Single Mixed Bed DI Stage with Refillable Cartridge

Single Mixed Bed DI Stage with Refillable Cartridge

Single Mixed Bed DI Stage with Refillable Cartridge

Waste to Product Water Ratio
Rejection Rate
Flow Restrictor 550 ml/min 800 ml/min 550 ml/min 800 ml/min
Auto Shut Off Valve ? ? ? ?
Canister Wrench ? ? ? ?
Laundry Tub Connection Adapter
Chrome Faucet Diverter Valve
HM Digital DM-1 TDS Meter
Membrane Flush Valve ? ? ? ?
Glycerin Filled Pressure Gauge ? ? ? ?
RO/DI Body Dimensions 16" x 6.25" x 15.5" 16" x 7" x 15.5" 16" x 7" x 15.5" 16" x 7" x 15.5"
Recommended Minimum Water Pressure  50-80 psi 50-80 psi 65-80 psi 65-80 psi
Tubing Size 1/4" RO Tubing 1/4" RO Tubing 1/4" RO Tubing 1/4" RO Tubing


Choosing the right RO/DI

Selecting the right RO/DI system might be intimidating at first but it really just boils down to a few factors. The main difference is the number of stages; most value systems being four stages and more advanced units with five or six stages.

If you have well-water or know for certain that your city uses only chlorine as a disinfectant and believe the water from your tap is reasonably clean with a low total dissolved solids (TDS) reading, a four stage unit will do the job.

If your feed water contains chloramines and/or contains higher levels of nitrate or phosphate, you should probably consider a system with multiple carbon blocks and DI stages for optimal product water quality and filter cartridge life span.

Water Analysis Report

The reason is that chloramines are troublesome and difficult to remove because they are much more stable than chlorine alone. You absolutely need to remove chloramines (ammonia reacted with chlorine) before the water goes into your tank. Without the proper RO/DI system and filters to go with it, chloramines will almost immediately deplete standard carbon blocks and DI cartridges.

Chloramine Molecule

Typical carbon block filters are almost worthless in terms of removing chloramines. We proved this to be true when we tested the most trusted carbon block filters on the market. The results showed that more than half of the total chloramines were being allowed through these standard carbon block filters within the first few hundred gallons of production.

BRS Carbon Block Filter Test Results Graph

When chloramines make it through the carbon block stage, they pass right through the RO membrane because of the small molecular weight. The chloramines then hit the DI cartridge and quickly deplete the resins.

BRS 6 Stage RO/DI Filter System

To solve the issue of chloramines, you want to double up on the carbon block filter stage and use the appropriate chloramine-rated carbon block filters. These chloramine carbon block filters do cost a few dollars more, but when set up in this manner, you will likely get a few thousand gallons of production before the filters need to be replaced.

In situations with higher phosphate and nitrate, which is common around farming communities in which fertilizer run-off increases these levels, you want to double up on your DI stage.

The DI cartridge is depleted from the bottom up, which means there is a full ten inches of charged resin the water is going to pass through. Once the DI resin is fifty percent depleted the contact time the water has with charged resin, and therefore the ability to remove contaminants, is cut by half. Only worsening in time, some level of nitrates and phosphates will surely be allowed to pass through the DI resins.

BRS Value to Deluxe Upgrade Kit

With two DI cartridges, the second stage will catch anything that passes through the first as it becomes depleted. Once the first stage is > 75% depleted, simply move that second filter into the first stage and replace the second DI canister with a brand new DI resin filter cartridge. This will maximize your filter dollars and ensure your water is clean and free of impurities at all times. If you already have a standard 4 stage system, both the dual DI and carbon block upgrades can be accomplished using the BRS Value to Deluxe Upgrade kit.

BRS RO/DI System Options

Bulk Reef Supply RO/DI Systems

A shameless plug, yes, but we worked hard to create the best RO/DI systems the aquarium market has to offer and we challenge you to find something better and tell us about it! If it exists, BRS will surely do everything in our power to match it.

Mur-LoK Fitting Features

Most of the RO and RO/DI systems out there use cheap imported push-connect fittings which cost around ten cents each. Leaking is the biggest risk with RO systems so we chose US-made Mur-lok brand fittings that have double o-rings and cost around $1 each.

BRS RO/DI System Accessories

We also include more installation accessories than anyone else, so it works when you get it and you are not stuck running to and from your local home improvement store for confusing plumbing parts that nobody has heard of.

BRS RO/DI System included filter cartridges

We include top-quality sediment, carbon block, and RO membrane filters from known brands you already trust like DOW, GE and BRS. All of which are NSF certified which is an important component of maintaining quality standards. All of these filters are going to perform better than a no-name brand, imported filters found on competing systems.

We offer a limited lifetime warranty that is backed with a knowledgeable customer service team that knows RO/DI systems and how they work. Behind that, we have at least twenty to thirty helpful videos directly related to RO/DI systems and how to maximize the quality of water, lifetime of your filters and troubleshoot when needed.

The cherry on top is we offer all of these awesome features at the lowest price points on the market and offer multiple systems to suit your particular situation. After all, our goal here at BRS is to make reefkeeping fun and easy for everyone!

What is the best salt mix?

What is the best salt mix?

The one answer that everyone wants. There just isn't a clearly defined BEST salt mix because hobbyists have varying degrees of success with all of them. What we can share with you is the distinct differences between some of our preferred salt mix brands so you can select one that aligns with your style of reefing.

  • Instant Ocean - Budget friendly option that has long been a staple in the reefing industry. Includes a heavy metal detoxifier to eliminate harmful metals commonly found in tap water. Two different formulas to accommodate both fish only and reef aquariums.
  • Red Sea - Takes a natural approach by using naturally harvested food grade salts evaporated from the Red Sea that is then enriched with all of the necessary elements to create a homogeneous salt mix for a saltwater aquarium. The Blue Bucket formula emulates natural reef water parameters and perfect for seasoned hobbyists with successful major element supplementation practices. The Coral Pro formula is great for beginners who still rely heavily on water changes for major element replenishment because of the elevated levels of calcium, alkalinity and magnesium.
  • HW Marinemix Reefer - A 50 year old German brand that uses 100% synthetically processed salts to create the purest salt mix available without any residual impurities that are typically found on evaporated or mined salts. The pharmaceutical grade pure ingredients means it does cost a little more but also eliminates the need for any special additives such as clarifiers, chealators, or anti-caking agents. It dissolves fast and clear without leaving behind brown crust in your saltwater mixing bin. The addition of amino acids is also somewhat unique and helps with a variety of biological processes.. HW Marinemix is commonly used by research and seafood/aquaculture facilities around the world and widely accepted to be one of the best salt mixes available. It also just so happens to be what we use here at the Bulk Reef Supply office.


Saltwater mixing station

Mixing saltwater

Once you select your salt, mixing it up is pretty easy. Most reefers will use a large BRUTE trash can which are considered to be reef safe, are heavy duty and has optional caster wheels for easy transporting.

You can create a more permanent water production and mixing station with the use of food grade plastic barrels or a Norwesco brand water storage tank. Adding a small heater and powerhead is best in order to thoroughly dissolve the salt mix and bring your water up to temperature before going into your tank. Just be sure to follow the manufacturer’s instructions precisely which we learned to be very important in a recent BRSTV Investigates episode.

Refractometer options

Using a refractometer is really the only reliable way to measure the salinity that should measure 35 PPT or 1.026 Specific Gravity when mixed properly. They come in a manual version which is affordable and accurate but you can also choose a fancy digital refractometer for an instant digital readout.

RO/DI System under sink connection diagram

Connecting your RO/DI system is fairly quick with various connection options including under your sink (shown above), garden hose and faucet connections. If you are not comfortable plumbing the system and would like a permanent install, a local plumber may be best to get the job done correctly. Just don’t forget to flush the filters before collecting water for the first time with the use of a flush valve.

When filling your tank for the first time, you can mix the water directly in your tank without doing any harm but once you have fish and corals, the water does need to be mixed in a separate container first and it is best to heat it to match your tank water.

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