What do RO and RO/DI units do? Do you need an RO System or an RO/DI System? How many stages? What do you need to do to your RO water before adding it to the tank?

What do RO and RO/DI units do?
RO and RO/DI systems remove contaminants from tap water, making it safe for use in an aquarium. They range from very simple ones with just a sediment pre-filter and carbon filter, to five-stage RO/DI systems with a sediment pre-filter, carbon filter, two DI cartridges and a TFC membrane.

• The TFC membrane removes calcium and magnesium (which make up general hardness, GH) and any carbonates (that make up the carbonate hardness, KH). This leaves you with truly soft water.
• The Sediment pre-filter is a fine (1 or 5 microns) mechanical filter to trap large particles and some bacteria in the water.
• The Carbon pre-filter removes large particulate waste and chlorine from the water. This is especially important with TFC membranes, as the chlorine will degrade their performance.
• The Deionization (DI) cartridge found in RO/DI units removes some other chemical compounds often found in the water--primarily nitrates, phosphates, and silicates.

How do RO Systems work?
The RO TFC membrane operates as a semi-permeable membrane that is placed under pressure (from the water supply) to cause water to pass through the membrane in a Reverse Osmosis direction, producing pure, soft water.

What are the RO System maintenance costs?
The sediment pre-filter, the carbon cartridges, and the Deionization (DI) cartridge will need to be replaced after about 6 months or approximately 1000 gallons of RO water produced, depending on local water conditions. The RO membrane should be good for approximately 3 years.

What types of aquariums should use RO water?
All aquariums should use RO water because tap water contains many impurities. These impurities include phosphates and nitrates, which fuel algae growth. Copper--highly toxic to invertebrates--can be leached from household pipes.

What needs to be added to RO water?
Because an RO system will remove almost everything from the water, you will need to add back some essential minerals. Marine aquarium salt mixes all contain these essential minerals. For freshwater use, you need to add back electrolytes, as the RO water will be too pure for the fish or plants. You will also need to add some type of buffer to prevent wild fluctuations in the pH value.

How pure does your water need to be?
The water you add to your aquarium needs to be pure. Very pure. Pure water has the following parameters:

• Ammonia = 0.0
• Nitrite = 0.0
• Nitrate = 0.0
• Phosphate = 0.0

Do You Need An RO System or RO/DI System? And How Many Stages?
We recommend all saltwater aquariums and all planted tanks use RO/DI water. In reef aquariums, the intense lighting needed to keep corals alive combined with the extra nutrients in tap water can cause excessive algae growth, even with algae-eating snails and crabs in the aquarium. In saltwater fish-only aquariums most common fish will eat the snails and crabs that help to limit algae growth. Even with the low lighting levels of fish-only aquariums, tap water can lead to excessive algae growth because no snails or crabs can be added to control it. We carry several RO & RO/DI Systems from IceCap, AquaticLife, and SpectraPure. RO or RO/DI water can also be purchased from local fish stores, “Water and Ice” type stores, as well as coin operated machines in front of the grocery store.

Many aquarists who look into purchasing a new reverse osmosis system are overwhelmed by the wide variety of options and prices. This guide will help you better understand the differences between different RO systems, and explain the functions of various RO accessories.

Two Three Four or Five-Stage – Reverse osmosis systems are often described by the number of filtration stages that they have. Some have 2 stages, some 3 stages, and others 4 or 5 stages.

Two-stage systems have a primary mechanical filtration stage followed by a carbon filtration stage. The mechanical stage removes particulates from the water by trapping them just as your air filter removes particulates from the air. The carbon stage removes a wide variety of heavy metals and toxins but most importantly it removes chlorine and chloramines which are extremely toxic to fish. Two-stage filtration systems are suitable for basic freshwater aquariums and drinking water.

Three-stage RO systems like the AquaticLife RO Buddie 100 GPD Reverse Osmosis System have the mechanical filtration and carbon plus an RO membrane. The RO membrane removes between 95% and 99% of all dissolved solids in the water. These systems are best suited for freshwater-planted aquariums and saltwater fish-only tanks.

Four-stage RO/DI systems such as the Ice Cap 4-Stage RO +DI, AquaticLife Twist-In Compact 4-Stage RO/DI Unit 100 GPD, and SpectraPure Line Pressure Reverse Osmosis/Deionization Four-Stage MaxPure MPDI 90 GPD System have the first three stages plus a deionization stage that produces 99.9% to 100% pure water. These systems are the best choice for reef aquariums.

Five-stage RO/DI systems such as the SpectraPure Line Pressure Reverse Osmosis/Deionization Five-Stage MaxCap Manual Flush 90 GPD System, and SpectraPure Line Pressure Reverse Osmosis/Deionization Five-Stage MaxCap Manual Flush 180 GPD System, include everything in the four-stage systems plus an extra deionization stage which does not produce cleaner water but will reduce the need for replacement media. These are best suited for reef aquariums where efficiency is a priority.

Other RO Products & Issues To Consider
TDS Meters – Some reverse osmosis systems, such as the SpectraPure Line Pressure Reverse Osmosis/Deionization Five-Stage MaxCap Manual Flush 90 GPD System, include TDS meters. TDS meters allow you to see what the purity of water is at particular points in your reverse osmosis system. This information can be used to notify you when you need to replace the filters in your reverse osmosis system, or to confirm that the water you are using is sufficiently pure. You can also add a TDS meter to your system if it doesn’t come with one out of the box. The SpectraPure Dual TDS Meter has two sensors and can measure the water purity after the RO membrane and after the DI resin to let you know how both stages are performing.

Booster Pumps – Reverse osmosis systems function better when there is high water pressure going through the reverse osmosis membrane. Higher pressure can help your system remove more pollutants and use less wastewater. Booster pumps such as the AquaticLife Smart Buddie Booster Pump for 50 to 100 GPD RO Systems can be purchased separately. If you make lots of water, have low home water pressure, or want to waste as little water as possible, then use a booster pump.

Auto Shut-Off Kits – Auto shut-off kits are a combination of two specialized valves that allow your RO system to automatically turn off once the reservoir you are filling is full. They use a float valve to sense when the reservoir is full and an auto shut-off valve to turn off the flow once the float valve is triggered. This can be a home and marriage saver as wet floors that result from forgetting to turn off your RO system can cause considerable damage. Auto shut-off kits are typically purchased as an RO accessory separate from the RO system. An example is the AquaticLife Float Valve for RO & RO/DI Systems.

Installing Your RO System – There are several ways to install an RO system and begin making ultra-pure water, but we will cover the three most common installation techniques.

Attaching your system to a garden hose - If you want to use your RO system outside then you can connect your RO system to your garden hose. You will need a garden hose adaptor to attach the systems supply line to your garden hose. Once you have attached the supply line to the hose you should have 2 more lines. The clean water line goes to the reservoir you would like to fill and the dirty water line goes out to your yard. The advantage of this installation is that the dirty water that is usually wasted is used to water your lawn where plants will use the pollutants in the water as fertilizer.

Attaching your system to your faucet - If you would like to use your RO System inside then you can attach the supply line to you faucet with a faucet adaptor. The waste line can then go down the drain and the clean water line goes into the container you would like to fill. This is the easiest installation for most users.

Installing your RO System under your sink – If you want a more permanent and professional installation then you can install a reverse osmosis system underneath your sink. For this style of installation, you will need to place a T fitting where your cold water supply feeds your sink. One end will go to your sink and the other will be the supply line to your RO system. You will also want to include a ball valve before your RO system to be able to turn on and off the RO system. The waste line attaches to your sink’s drain using a saddle fitting. And the clean water line goes to the container you would like to fill.

We recommend all saltwater aquariums use RO/DI water. In Reef Aquariums the intense lighting needed to keep corals alive combined with the extra nutrients in tap water can cause excessive algae growth, even with algae-eating snails and crabs in the aquarium. In saltwater fish-only aquariums most common fish will eat the snails and crabs that help to limit algae growth. Therefore, even with the lower lighting of a fish-only aquarium tap water can lead to excessive algae growth because no snails or crabs can be added to control it.

Water for Top-Off

• RO Systems will remove most of the minerals in your water. If you’re just replenishing water lost to evaporation then untreated RO or RO/DI water is perfect (as the minerals do not evaporate).

• Most salt mixes used for filling tanks or for water changes are formulated for RO and RO/DI water. You may want to test your freshly mixed salt water and add buffer and calcium as needed before adding to the tank.

• RO & RO/DI water for freshwater aquariums should be treated with some type of buffer before adding it to the tank. For specialty tanks, we suggest looking at the offerings from Seachem and Brightwell, such as Seachem Discus Buffer, Seachem Brackish Salt, Seachem Cichlid Lake Salt, and Brightwell Florin Delta KH+.

• Test your RO water periodically with a TDS Meter. This will give you an added level of confidence in the water you’re adding to your aquarium, and let you know when it’s time to change your RO System cartridges. Some RO Systems come with a TDS.