Reverse Osmosis vs Tap


As you can tell, my two conflicting LFS, have me throughly confused! One insist that I start immediately using R/O if, I expect to be successful with my reef tank (currently geeting to a position to start adding corals). The other says tap water will work just as good, as long as I dechlorinate it before water changes, top offs, etc. One LFS will only guarantee his livestock,(which by the way looks really great), if I make the change to R/O. Any input would be appreciated.


R/O water is supposed to be the best you can have. I would make the switch for the guarantee because you don't get many of them in this hobby.


RO water is better than tap water. You really don't know what chemicals other than chlorine come in your tap water unless you get it analyzed in a lab. RO will at least assure you that you are not using those chemicals. You, however have to maintain your RO unit by changing the filters regularly.


Tap water with a dechlorinater would be fine in a fish only system. If you want corals then definitely use R/O. Tap water can contain metals that can kill certain corals.
R/O will remove these metals making it safe for all corals. To be extra safe use R/O-D/I.
Remember if you want a healthy reef you must firsts start with good water.
This article explains exactly why I only use RO water in all my tanks and why I prefer to mix my own saltwater with ro as opposed to getting filtered sea water. Good for all to read.Although this is an article,It has been deleted because it is an online store.....No store links remember...SALTY
[ April 27, 2001: Message edited by: Saltwater Marauder ]
[ April 28, 2001: Message edited by: MR . SALTY ]


Active Member
If your tank is of reasonable size then you could use the Jack Watleys Tap Water Purifier. It works great, cost less, doesn,t waste water and is easy to use. I've been using it on my 29gal reef since we have phosphates here in Ct. I figured so far it's cost me 6 cents per gallon. I have 13 different corals in the tank and they lub the water.


Want a cheap way to get ro/di water that is dechlorinated, and this and that and blah blah blah?! Go to your wal-mart (or wherever) and get refills of Culligan for like 30 cents/gallon! Cheap and easy!
HTH :cool:
Fair enough, here it is in its entirety, without the link.
When setting up or maintaining an aquarium, one inevitable is that you need water. In fact, for a marine aquarium, you will need a supply of both fresh and saltwater. The saltwater is used to set up the tank and for water changes. The freshwater is used to top off evaporated water in order to maintain the water level in the aquarium. (Since only water evaporates, leaving salt and other dissolved solids behind, topping off with saltwater would increase salinity.) So, where do you get the water?
Natural Sea Water vs. Synthetic Salt Water
You have two choices for supplying saltwater -- natural seawater or synthetic water made by mixing prepared marine salt mix with freshwater. Natural seawater is only an option if you live in a coastal area. For example, here in San Diego (home of The Reef Web), filtered off-shore seawater is available free to hobbyists courtesy of the Scripps Institute of Oceanography.
Regardless of whether seawater is taken from the beach or carefully filtered and drawn from off-shore sources, it should be disfavored. Synthetic saltwater made with pure freshwater and a quality salt mix is preferable for several reasons. First, seawater however carefully filtered may contain pollutants or other contaminants. Second, seawater will contain plankton that can die while the water is stored and pollute the water. Third, synthetic water contains increased levels of buffers and elements that are quickly depleted in artificial marine systems. (Since mother nature does not have to deal with the shortcomings of an artificial environment, natural seawater is not maximized for aquarium use.) As a result, synthetic water lasts longer and holds up better between water changes. In light of these factors, we recommend using synthetic water unless your system is so large that economics require a free source of saltwater and you have access to carefully filtered and purified seawater.
Freshwater Options
If you choose to mix your own synthetic saltwater -- as most aquarists do -- you will need a good source of freshwater both for mixing saltwater and for top off. There are four primary options. You can use tap water chemically treated to remove certain toxins. You can purchase purified or distilled water. Many aquarium stores sell reverse osmosis (R.O.) or de-ionized (D.I.) water. Finally, you can obtain and set up your own water purification system. Each of these options is discussed below.
Tap Water
Tap water has been used for aquariums for as long as people have kept aquariums and had running water. This simple method requires adding a chemical water conditioner (such as Prime, Am-Quel or Nova Aqua) to remove toxins like chlorine, chloramine and other heavy metals. If the pH of the tap water is not in the proper marine range (8.0 - 8.4), pH buffers must also be added. The water is then mixed with salt mix, aged and then used in the aquarium.
Use of tap water is the least preferred of the four freshwater sources discussed here. Tap water contains significant contaminants other than those removed by commonly available water conditioners. For example, a recent water quality report for a San Diego area water district revealed the following standards:
Additive or contaminant
Aluminum 0.114 ppm
Copper 0.6 ppm
Flouride 0.24 ppm
Lead <5 ppb
Nitrate 0.21 ppm
Radioactive particles (excluding Tritium) up to 4.7 pCi/L
Tritium 384 pCi/L
Chloride 71 ppm
Total Hardness 221-333 ppm
Sulfate 190 ppm
r />
These levels are very low compared to some water districts in the United States. Nevertheless, even these levels can create problems in aquaria. The copper level alone can significantly impair a reef system and can be toxic to invertebrates. The nitrate level, while very low, can accumulate in a closed system. While the radioactivity levels are very low, is this really what you want to add to your reef? Although data was not available from the subject district regarding phosphates, our tests revealed high enough phosphate levels (appx. 0.3 ppm) to cause algae blooms.
More importantly, there are no guarantees of consistency with a municipal water district. If the source water experiences an algae bloom, the district may increase chloride levels or add herbicidal agents to control the bloom. As long as the additives are safe for human consumption, the district presumably would have no obligation to inform you of the addition. Such an additive could wipe out your precious reef system before you knew it was there.
In light of the variable and unknowable nature of tap water, it cannot be strongly recommended for aquarium use. This is especially true for systems housing very sensitive invertebrates.
Bottled Water
Bottled purified or distilled water is a better option than tap water. Many bottled waters are purified using R.O. or D.I. purification. There are, however, several drawbacks.
First, drinking waters often contain added minerals (commonly calcium chloride, zinc and magnesium). While these are mostly harmless to aquaria, calcium chloride can impact salinity, interfere with alkalinity reserves and cause other reactions in the aquarium. Even though many reef aquarists intentionally add calcium chloride, it would be very difficult to properly dose such an additive if it was present in your source water in an undisclosed concentration. Distilled water does not contain such additives.
Second, the cost of bottled water generally is prohibitive except for very small systems. Consider a 100 gallon tank that utilizes 30 gallons per month for makeup water and an additional 25 gallons for replacement salt water. At $1.00 per gallon, supplying bottled water would cost $55.00 per month. In three to four months, the cost would pay for a good quality R.O. unit.
Finally, although the water may have been carefully purified, it was then stored (possibly in several vessels before being bottled). The storage and handling vessels may have been metallic or contained other harmful elements, some of which may have permeated the water. We have all smelled or tasted the plastic of a water container in bottled water. Unless you know what causes that smell to remain in the water, there is some element of risk in its use.
R.O. or D.I. Water From the LFS
Many aquarium stores now sell R.O. or D.I. water. This is a perfectly feasible, although inconvenient option. While such water is generally inexpensive and trustworthy, obtaining and transporting it is inconvenient. It generally requires purchasing enough large containers to make the trip worthwhile and lugging the heavy containers from the LFS home. Often, the cost of enough containers to minimize trips would go a long way toward the purchase of a reverse osmosis filter.
Home Purification
As you may have figured by now, home purification is the way to go for source water. R.O. and D.I. units are widely available at a wide range of prices.
A good water purifier can remove virtually all foreign matter from water, including all elements commonly found in tap water. The resulting water is truly pure and can be used either for top off or to mix saltwater. (Purified water should not be used for freshwater dips without first buffering the ph.)
Using purified water for water changes and top off can help maintain low levels of nitrates, phosphates and silicates. Since reducing these levels can help control algae, a water purifier can often improve the appearance and reduce the maintenance of a tank.
There are three types of water filters commonly used for aquaria. A basic reverse osmosis unit will remove from 80 to 100% of most of the compounds and elements commonly found in tap water. These units tend to be the least expensive of the purifiers discussed here. Their biggest drawback is that some may only remove 50% of nitrates and 80% of silicates. As many municipal water sources have high concentrations of both of these algae-supporting nutrients, this may be inadequate to control algae growth.
Kent Marine offers R.O. units with a specially designed "Hi-S" membrane. This membrane increases the removal rate of the filter to 98-99% of virtually all undesired additives commonly found in tap water.
Kent Marine Hi-S Reverse Osmosis Unit (60 gpd model)
Hi-S Unit
The Reef Web Wide view, showing connection to reservoir (cover removed to show water level, controlled by float valve)
The Reef Web
A deionization purifier removes very close to 100% of all contaminants, leaving completely pure water -- just H2O. These units are preferable only if your tap water is extremely high in nitrates, silicates or phosphates. Otherwise, they are not worth the added cost and maintenance.
There is one other considerable difference between R.O. and D.I. units. R.O. membranes produce much waste water -- approximately three gallons for every gallon of purified water. A D.I. unit, by contrast, wastes no water.
Unless you live in an area with poor enough water quality to justify a D.I. unit, we recommend the Kent Marine Hi-S R.O. unit.
[ April 30, 2001: Message edited by: Saltwater Marauder ]


Great article .. I was a skeptic at first because the article probably posted on the Kent website. However, I did check the copper level with my water company.
Copper Level:
- My Water Company = .123 ppm (WSSC 2005 Tap Water Report)
- IO Salt = .006 ppm (advanced aquatics, Dec 2005).
At .005ppm, coral growth is impacted per