Why you should only use RO Water for your Aquarium

Why you should only use RO Water for your Aquarium

Why you should only use RO Water for your Aquarium

Science tells us the same water has been on Earth since its creation.¹ That’s 4.6 billion years of our water going through the same cycles.¹¹ Think it’s picked up anything along the way? Of course, it has.  That’s why we have a government that regulates the quality of our drinking water.¹° With that being said, it’s important to know what’s in your water.
We recommend only using the highest-quality, RODI water (reverse osmosis deionization) for any fresh or saltwater tanks We know the added cost of an RO system in your home might be a little pricey, and it might be an inconvenience to make an extra stop by your local pet store for an RO water fill up. But we promise it’s worth it for you and your fishy friends. We’ll tell you why here.


There are various ways to filter water, but the three we’ll be examining today are

  1. Natural Water Filtration During the Water Cycle
  2. Tap Water Filtration at Treatment Facilities
  3. Reverse Osmosis Water Filtration at Parrott Aquatic


What's in Your Water?


Let’s start by taking a look at how many contaminants are found in each type of water.  But first, we must understand what a contaminant is.  The Safe Drinking Water Act defines water contaminants as any physical, chemical, biological, or radiological substance or matter in water.¹² That means chemicals you thought were good, like chlorine and fluoride, are also considered contaminants.


Untreated water contamination is directly affected by soil absorption, living organism use, living organism decomposition, human activity and many other factors.  All of these play a role in the number of contaminants found in untreated water. Some of those contaminants are

  • Pollen, Dust, Debris picked up during precipitation or runoff phases
  • Acidic Ph balance from collecting impurities in the air
  • Chemicals from air pollution
  • Heavy metals from runoff water


Tap water begins as untreated rainwater and goes through a treatment process.  Even after water treatments, your tap water may still contain amounts of

  • Bicarbonates
  • Chloride
  • Fluoride
  • Sulfates
  • Nitrates
  • Heavy Metals



  • 0 Total Dissolved Solvents (TDS)




If your tank is exposed to poor water quality with contaminants listed above, expect to see some of the following problems.

  • Cyanobacteria is a red slime bacterium that grows when excess nitrates and phosphates are found in your water. RO water has 0 contaminants, so it eliminates the bacteria’s food source.
  • Nuisance algae like brown and green algae enjoy excess nitrates and silicates. RO water reduces the growth of nuisance algae because it does not contain any nitrates or silicates.
  • Poor fish and coral health 
  • Tank “recycling” means a new ecosystem must be reestablished after a tank crashes and loses its initial ecosystem. Professionals will test the water and develop a plan that usually includes water changes and manually removing algae.
  • Trigger stress-related diseases like ick in your fish (Remember: All tanks contain some level of ick!)


RO Water Timeline


In nature, water travels through its natural water cycle which takes places in 4 major stages. This is actually way oversimplified, but for time’s sake, we’re going to look at the grade school version.

  1. Precipitation: Snow and hail warm and turn to rain as it falls to the earth’s surface from clouds oversaturated with water molecules.
  2. Runoff: Water runs across multiple surfaces on Earth.  The first step in natural filtration occurs when water runs across porous soils like sand and gravel.  Less porous soils like clay cause water to pick up heavy metals like iron.
  3. Evaporation: Evaporation occurs when water sources heat up.  Filtration occurs during this phase through a process called photolysis. As the water warms up, it turns to air, passes back into the sky.
  4. Condensation: When the water reaches the sky, it cools, and condenses into snow or hail waiting for the cloud to become too heavy and begin the process over.

THE IMPORTANCE OF WETLANDS: Wetlands are crucial to water filtration.  They are shallow pools of freshwater with a thick mat of sediment at the bottom. The sediment is filled with bacteria, plants, and other microorganisms that break down and use some of the organic contaminants found in the water.  The remaining heavy organic contaminants are broken down by the sun’s rays through a process called sunlight photolysis. Because photolysis is so effective at removing heavy organic contaminants, scientists are currently strategizing on similar methods to speed up the process and filter more water. (4, 8)

After going through this a few times, you can imagine how many contaminants are probably left in the water.  That’s why humans developed a way to chemically balance water to make it safe for drinking.



Tap water begins with the same contaminants found in the untreated water, but are filtered through chemical processing to have much fewer contaminants. Treatment plans vary from state to state as different water has different chemical balancing needs, but let’s take a look at a typical water treatment plan.

  1. Add chlorine to the untreated water source to kill any bacteria.
  2. Add aluminum sulfate to make organic particles stick together.
  3. Let the water sit in a reservoir to allow organic matter to settle.
  4. Filter water through multiple sand filters.
  5. Add lime treatment to balance ph levels.
  6. Store for consumer use.


Tap water is chemically treated by introducing new chemicals to balance the water to a safe drinking level. Although most tap water is considered safe drinking water, it’s important to remember there are still contaminants in it.


A government body called the EPA helped pass the Safe Drinking Water Act in 1974, and began regulating water quality for U.S. citizens, setting standards for safe drinking water across the nation.(12) Water is still currently regulated by the EPA at treatment facilities across the country.

The EPA allows “acceptable amounts” of chemicals in our water because they are caught between the risk contaminants actually pose to human health and the cost to completely remove all contaminants from drinking water. (13) They a primary set of guidelines that are measurable and enforceable, but they have secondary contaminant guidelines that aren’t enforceable and contribute to poor drinking water quality. Although the EPA cannot afford to remove all contaminants from our drinking water, they continue their goal of informing the public, by publishing their yearly reports on local water quality and make them available for consumers online.



To ensure you have the purest water, confirm it’s filtered by reverse osmosis.  It’s probably best to explain reverse osmosis by reading a quick refresher on osmosis.

OSMOSIS: In nature, plants suck up nutrients and water passing them through a semi-permeable plant membrane to water within the plant with higher chemical concentrations. This is osmosis. The process of water with lower concentrations of chemicals passing through a semipermeable membrane to combine with water of higher chemical concentrations.

REVERSE OSMOSIS: Simply enough, reverse osmosis is passing water through a semi-permeable membrane to remove chemicals from the water. This process removes ionization and particles from your regular tap water by passing it through multiple semipermeable membranes and filters. It is measured by the number of Total Dissolved Solvents (TDS) found in a solution with the purest water measuring at 0 TDS.

RO System_Final 01

An RODI Filtration system is crucial to your tank’s water quality.  A standard RO filtration system has 4 steps; however, Parrott Aquatic operates on a 10-step filtration system to provide the highest water quality for our customers.

  • FILTER 1 (Not Pictured): Tap water enters the large sediment filter (not shown) which catches larger particles in your water.
  • FILTER 2 (Not Pictured): Tap water enters a carbon filter.
  • FILTER 3-5: Water travels through several sediment filters which remove contaminants like chlorine.  Our filtration process at Parrott Aquatic has a few extra carbon filters.
  • FILTERS 6: Water travels through a semipermeable membrane (top left).
  • FILTERS 7-8: The last two filters your water passes through is the De-ionization part.  The membrane consists of multiple thin layers, and removes any salts, bacteria, or other contaminants.
  • FINALE: During the grand finale, our purified water is funneled to a holding tank, where it can be turned into saltwater.


We prefer AquaFx filters for our purified water at Parrott Aquatic because they are the leaders in reverse osmosis. Founded in 2000, AquaFx manufactures commercial and home-based filters right here in the U.S. (5)


  1. Raise water temp in the saltwater vat to between 70-75 degrees
  2. Turn on mixing pump
  3. Mix .5 cup salt/gallon of RO water
  4. Keep water moving the entire time you’re slowly adding salt.
  5. Slowly add salt to keep from building up in the bottom of the mixing vat.
    • Pro Tip: We cut a small hole in the bag, and allow it to sift into the vat using gravity. This uses less effort than having someone hold the bag from on top.
  6. Mix until you reach desired salinity level.

 If you’re an aquarium beginner, you may be wondering, “Can’t I just throw some table salt in this thing to get it going?” The short answer is no, No, NO. The long answer is below.

Although Instant Ocean seems to be a popular choice for saltwater tanks due to affordability, at Parrott Aquatic, we prefer to use Fritz salt because we trust their meticulous research.

Fritz began their research for the perfect aquarium salt by working with public aquariums and experts nationwide to determine the right base for their blend. Once they perfected their base, they reached out to us, the public, to determine the remaining balance.  After speaking with “reefers” from all over, they determined the most ideal water conditions for a saltwater tank. Then they produce their carefully balanced salt blend in-house in small batches for total quality control.


Reverse osmosis filters water to its purest state of 0 TDS which helps aquarium owners like yourself reduce the risk of introducing contaminants to your inhabitants. Other companies are noticing the difference in water filtration methods and are making the switch.

Take Aquafina, for example.  I remember their water tasting like chemicals for years which is ultimately why I quit drinking their water.  When I worked in retail, I remember an Aquafina delivery person telling me not to put their water on the shelf until after it’s cured for 72 hours off the line. WHY SHOULD I EVER HAVE TO LET MY BOTTLED WATER CURE?!

Recently, I was in a pinch for some water. I could have chosen between heavy Dasani mineral water or Aquafina.  Normally I would have chosen Dasani even though I hate mineral water, but I noticed something on Aquafina’s label that made me change my mind. “Filtered by the power of reverse osmosis.” I’ve been learning about RO filtration systems for about a year now, so I decided to give it a try.  It was amazing.  It tastes like every bottle of water should taste like – nothing.  Light, refreshing, crisp, tasteless, nothing.


RO is the way to go! Contaminants contribute to algae and bacteria outbreaks, poor fish and coral health, and overall stress on your tank. Setting up your own reverse osmosis system ranges between $150-$300, but you can purchase RO Water (Fresh & Salt) from Parrott Aquatic for about .40/gal – .80/gal.


Give us a call at (865) 253-2846 to pick up fresh or salt RO water for your tank from Parrott Aquatic. We have a self-service fill-up station for your convenience.


  • Parrott Aquatic is equipped to produce 1000 gal/day of 0 TDS, reverse osmosis water for our customers.
  • It is unsafe to drink deionized water for long durations due to the risk of electrolyte imbalance.
  • RO systems’ pressure should measure between 40-80 PSI for best filtration.
  • Our saltwater mixing vat features an 800-watt titanium heater and a mixing pump in the bottom that turns 4000 gal of ro water/hour.
  • Our goal salinity level is 1.02526.


1 https://www3.epa.gov/safewater/kids/waterfactsoflife.html

2  https://www.livestrong.com/article/256960-natural-water-purification-process/

3 https://www.freedrinkingwater.com/water_quality/quality1/1-how-water-is-filtered-in-nature.htm

4 http://berkeleysciencereview.com/article/natures-water-filter/

5 http://www.aquariumwaterfilters.com/

6 https://blog.marinedepot.com/education-center/charts-diagrams/reverse-osmosis-deionization-rodi-system-works

7 https://www.water-research.net/index.php/water-treatment/tools/total-dissolved-solids

8 https://www.freedrinkingwater.com/water_quality/quality2/j-8-08-natural-purification-of-liquid-water-work.htm

9 https://pmm.nasa.gov/education/water-cycle

10 https://www.freedrinkingwater.com/water-education3/32-water-tab-water.htm

11 https://news.nationalgeographic.com/news/2014/10/141030-starstruck-earth-water-origin-vesta-science/

12 https://www.epa.gov/ccl/types-drinking-water-contaminants

13 https://www.hydroviv.com/blogs/water-smarts/epa-regulations

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