Use of RO, DI, Softwater in Aquariums

 

INDEX of this article:

• Reverse Osmosis or DI Filter Information, Use
  AND Correct Use of RO, DI (or Distilled), or Rain water in Aquariums or Betta Tanks


• Why to NOT use Water Softener Water (or sodium based products) in Aquariums


• Necessary Minerals


• MUST READ Companion Article: Do Fish Drink? Osmoregulation in Fish

By Carl Strohmeyer-PAMR 35+ years experience


OVERVIEW:

While the use of Reverse Osmosis and/or De-ionized water has been around for quite some time, their use has exploded of late, often for good reasons, but unfortunately there is a lot of miss-information and gimmicky products that over sell the less experienced aquarium keeper.
I have used both types of equipment over the last few decades, and this includes variations within such as the use of Cellulose acetate membranes which are the oldest form of commercial RO membranes, yet still used in most RO and RO/DI combinations to keep the price MUCH lower!

Re-mineralization after use of RO and/or DI water and essential minor and trace elements/minerals is also discussed.

I also address the use of water that has passed through typical home/office water softeners and why the use of such water poses a serious long term threat to ANY fish' health.

RO (REVERSE OSMOSIS), DI (DI-IONIZED or DISTILLED), RAINWATER IN AQUARIUMS, OR WATER SOFTENER WATER

*First what is RO water?

RO/Reverse Osmosis water is simply water that is run under pressure through a micron pre-filter, then a carbon pre-filter & finally a osmonic membrane.
For reef keepers, these are often a must and at a cost of just pennies per gallon, often well worth the investment over paying .25 cents per gallon. For Discus keepers and similar biotope aquarium RO or RO/DI units can also be helpful.

The membrane is the most expensive part of a RO unit and is rated in gallons per day (gpd).
With water that is too hot or cold (the ideal operating temperature is between 70-80 F or 21-27 C), along with low water pressure (psi), and high TDS (total dissolved solids) all will combine to slow the rated capacity of a RO Unit & membrane. High TDS will also affect the life of the membrane.
Often the pressure provided by the tap water is adequate, however with high capacity RO Units additional boost pumps are required (usually units over 100 gpd which require 65 to 80 psi).

The few quality aquarium RO units still produced use TFC (thin film composite) membranes which is much better for removal of ammonia, phosphates, and TDS.
The other much more common type is the CTA, a.k.a. the cellulose triacetate membrane (sold by Dow) which is used in low cost RO units commonly sold by discounters such as Amazon & Bulk Reef Supply. Cellulose acetate membranes are the oldest form of commercial RO membranes and the lowest cost to produce, hence the much lower costs of systems utilizing these.
Both membranes are damaged by chlorine, which is one reason for the carbon pre-filter (canister).
The membrane should be changed every 2-3 years or 12,000-18,000 of total water produced (whichever occurs first).

A properly functioning membrane will work effectively after a 2-3 gallon break-in (throw this water out), after this initial start up, you should have 1 gallon of "good" water for every 3 gallons of reject water. If higher, this can concentrate molecules that the RO membrane cannot remove (which is why spending a few extra $$ for a good RO unit such as the TMC designed specifically for aquarium use is worth it, not looking for the best deal via eBay or Amazon).

RO System Product Resource: Tropic Marine Centre V2 Pure Reverse Osmosis System

TDS Monitor Resource: TMC Total Dissolved Solids Monitor

Generally speaking, a well maintained RO unit will reject about 97%+ of TDS.

*DI Unit; which stand for "De-Ionized".
Most commercially available DI units are simply a RO unit with an additional DI canister/chamber following the RO membrane (API makes a basic DI only unit though). This chamber utilizes resins that further remove TDS from water.
With this system, you can achieve 0 mineral cations and a TDS of 0 after starting with tap water over 250 TDS, while this same tap water run through a RO only unit would generally result in about 7 TDS at most with a quality RO only system.
You will also achieve a pH of 7 since a DI unit or chamber affects ionization where as a RO by itself does not.

For my purposes I found that a well designed TFC (thin film composite) RO only unit was/is more than adequate, however if you are making water for extremely sensitive purposes (such as a car battery), or have high ammonia levels in your tap water, a DI/RO unit may be the better choice for you over a RO only unit.
The reason is much of what the additional DI chamber/resin removes is mineral cations as well as all charged molecules (electrolytes).

Which is why DI water is better for a car battery, but these few mineral cations missed by RO only units are not a problem for any freshwater or saltwater aquarium (unless run off from a Home/Office Water Softener) and in fact these ions are generally beneficial.
As well the operating costs of DI chambers are very high as I have had to replace the resins in these chambers as frequently as once per week with some units under high use.

The bottom line is to NOT believe the hype some sellers of Four to Six Stage RO/DI units put forth and save your money (both initially and ongoing) and purchase a QUALITY TFC RO only water system which WILL result in 0 phosphates, 0 nitrates, and chloramines along with very low TDS readings with less reject water and lower operating costs.
There is a good reason some of these 4-6 stage RO/DI units can be sold at prices comparable to or even lower than top quality TFC 3 stage RO systems and and this is the use of lower quality carbon (instead of catalytic carbon) and use of Dow cellulose triacetate membranes!!!

Another test of an RO or RO/DI system/filter is if the reject water is higher than three gallons of water for every one gallon I would question the quality of the membrane used. This can result in concentration of ammonia as I have noted in experiments in the past.

There are really only two MAYBE reasons to purchase a unit that also features de-ionization:

1. If your tap water has high ammonia or is in a rare municipality that uses chloramines (such as some SW USA locations). An expensive to operate DI chamber are often are only good for about 50 gallons and make little difference for chloramines if well designed (some of the cheap Amazon/eBay units are not).
   
   If the RO unit is well designed using quality catalytic carbon (such as the TMC models), the fact is these will remove chloramines.
   
   References:
   *Removing Chloramines from Water
   *Catalytic Carbon for Chloramine Removal


2. You want to run your system directly off from a home or office water softener that uses sodium chloride or potassium chloride, since these systems radically alter the mineral ions in ways detrimental to fish and invertebrates (reference section about use of home water softeners later in this article). Even then, plumbing your RO system to your tap/well water source prior to entering the water softener may save you a lot of money over time!

Another method to prepare DI Water is to distil the water by boiling then collecting the condensation of this water (AKA distilling).

This can be an economical DIY project or there are commercial water distillers also available.
If you are making a DIY Water Distiller, make sure to use condensation collection coils & other related surfaces that will not add elements back into the water, especially copper coils (which can defeat the purpose of the water distiller).
Some plastics can also add chemicals back into your water, generally stainless steel is accepted to be the best surface to use for condensation collection. Please click on the picture to enlarge

Use of RO, DI (Distilled) water in Aquariums or Betta Tanks;

Do NOT use 100% RO water unless you are an advanced fish keeper with time on your hands, which includes having GH and KH Test Kits/Strips, as well as some basic knowledge or aptitude of chemistry.

Generally the use of RO or DI water in freshwater aquariums should be restricted to blending with tap or well water so as to "Cut" the water resulting in lower buffers and hardness of aquarium for use with Amazon River, Southeast Asia (such as Bettas), or similar fish.

Generally I start with 25% RO water and work up from this over time (if necessary).
The reason is that RO and similar water is NOT properly mineralized for correct osmoregulation with essential minerals such as calcium nor is there any carbonate buffers to maintain a stable pH which the lack there of would result in a roller coaster pH in the aquarium, often with disastrous results.

That said, for advanced freshwater fish keepers who desire exact Amazon River or SE Asia aquariums (or even Goldfish, Livebearers, etc.);
The use of 100% RO water can achieve phenomenal results providing all trace and major minerals as well as buffers are replaced (buffers are very often missed with users of 100% RO Water).
The reason is that you can reproduce the exact water conditions you desire (assuming again you are familiar with water chemistry), without starting from a point of incorrect minerals or even high nitrogenous organic compounds such as Nitrates (which are often found in tap water or well water).

Everything you need to know about water chemistry:
Aquarium Chemistry

With Marine Reef Aquariums, since most better salt mixes are exacting in their mineral and trace element blends, the use of RO water provides for better results.
More importantly, topping off for evaporation in marine aquariums with tap water (even fish only tanks), results in climbing nitrates, sometimes falling alkaline reserve, incorrect usable calcium levels, and more. So the use of RO or DI water is often a must in marine aquariums for evaporation from my experience.

Correct use of RO Water:

First, if small amounts RO Water (under 25-50%) is used to "Cut" hard/alkaline tap/well water, often only electrolytes with mild buffers already added such as SeaChem Replenish is all that is necessary, not strong buffers or baking soda.

For those considering using RO or DI water in higher amounts, it is important to note that for proper osmotic function trace amounts of several minerals are required.
Many of these supplied simply by water changes and supplements such as Wonder Shells.
For this reason pure RO (Reverse Osmosis) or Distilled water are not good for water changes unless re-mineralized (with products such as Replenish, Wonder Shells, and Buffers) or blended with tap or well water that is possibly too high in many minerals (a very high GH over 500 ppm can slow respiration in some freshwater fish).

To use with RO water:
*Aquarium Mineral Blocks
*SeaChem Replenish; water RO, DI mineral, carbonate replenisher
*SeaChem Aquarium Buffers

For Alkaline/Acid Buffer Ratios for use in Planted, Amazon, or SE Asian Aquariums (softer, low pH aquariums), please see the chart below (based actual ratios, NOT dosages):


*Please note that the above SUGGESTED Ratios are based on 100% pure water and in most instances the water used is not, especially if the Water is from a RO Filter that is not serviced regularly, or is simply a poor quality RO Filter (often one intended for human use, not aquarium use).
The bottom line is to start with these ratios, then adjust the rations until desired parameters are met; then write down these rations and use them in the future.

*As well as noted this is for low pH/softer water aquariums!!
For goldfish, livebearers, or even general community tanks, the use of Malawi Buffer (or Marine Buffer) is advised. Also the use of Acid Buffer as a counter buffer for equilibrium is generally not necessary.

*Do NOT use these ratios to adjust well, tap, blended, or established aquarium water!!
For this you need to add buffers as per aquarium parameters and then find a "Sweet Spot" where your aquarium maintains the desired parameters without a pH roller coaster. This often takes small doses until this is achieved.

*Finally these ratios are based on a starting measurement as per your tank size & suggested amount as per the buffer used (see your product instructions).
In other words if for your size aquarium 1 teaspoon is required of a certain buffer this becomes "1 Part" and then you would use 1/2 teaspoon if ".5 Part" of a counter buffer is also called for.

Products that can aid in re-mineralizing RO water (many can be/should be used with other products for complete re-mineralization that includes carbonates)

Basic Electrolyte Replenishing Products (& Links):

*SeaChem Replenish;
Similar to Kent RO Right and API ElectroRight as a primary trace element/electrolyte replenishing product, although this product does add some buffers.
I recommend using this product to add to RO/DI water whether used in full or to "cut" tap/well water. Use the directed amount for the amount of RO or DI water used, not the full gallonage of the aquarium.

*Kent RO Right;
This is for basic trace elements, electrolytes, this product does NOT add most necessary buffers and most major minerals that are especially necessary for general freshwater fish tanks, especially livebearers, African Cichlids, and Goldfish.

*Aquarium Pharmaceuticals Electro Right;
As with Kent RO Right, this is for basic trace elements, electrolytes, this product does not add most necessary buffers and most major minerals that are especially necessary for general freshwater fish tanks, especially livebearers, African Cichlids, and Goldfish.

KH Buffers & GH/Mineral Additive Products (& Links):

*SeaChem Alkaline Buffer and SeaChem Acid Buffer
These to products above are for balanced carbonate/bicarbonates for correct KH & pH.
These are generally used for planted or low pH/soft water aquariums.

*SeaChem Malawi Buffer (or SeaChem Marine Buffer);
This would be the buffer of choice (used as directed) for Livebearers, Goldfish, African Cichlids, and similar higher pH/KH fish. I suggest using 1/2 the recommended amount in your RO water prior to addition to your aquarium then add to this until the desired KH is reached.

*SeaChem Cichlid Salt
Similar to SeaChem Buffer along with added sodium chloride salts

*Wonder ShellsAn important compliment mineral replenisher; mixes well with Electro Right, Replenish, RO Right, SeaChem Buffer or the similar but much less easy to use, SeaChem Equalibrium.
The Wonder Shell is an excellent compliment to follow up with Replenish or other initial RO Water Electrolyte additives, so as to constantly maintain essential mineral cations.
I recommend to use 1/4, 1/2, or a normal size Wonder Shell based on the type of aquarium kept & mineral needs. This goes for 100% RO/DI regenerated water, RO/DI cut water or 100% tap/well water.


*SeaChem Equilibrium;
Similar to Replenish, Wonder Shells or AragoMight, but with much more emphasis on Potassium and thus planted aquariums. In most cases I have found this product NOT the better choice when compared to the use of Replenish along with 1/4 to 1/2 dose of Wonder Shells. WHY? My extensive use of Equilibrium has not achieved as good of results, even in planted aquariums since it does not maintain the mineral Cations required in a closed system nor is it as useful for RO water use.

These products can be used separately or together.
The API ElectroRight, Kent RO Right only adds important trace minerals and no carbonates and is usually inadequate by itself.
I generally would soak a Wonder Shell in RO water and then add Buffers (often both acid and alkaline for correct balance) or Cichlid or Marine Salt to further replenish major and minor elements as well as carbonates (as Wonders Shells have little carbonates).

Drinking Water/ Rain Water;

Also be real careful with water label “Drinking Water” (products such as Aquafina are simply RO water that has some minerals added for flavor for human consumption) as this is usually just RO water with a few minerals added for taste and does NOT have the electrolytes needed by fish. Usually pure spring water does have the proper electrolytes needed by fish.

I have seen many (especially on the internet) recommend rain water be used in place of tap water or similar, the reasoning is similar as with RO water that this water is more pure and therefore more healthy for the fish.
HOWEVER this reasoning is severely and dangerously flawed as rainwater generally has little or NO essential minerals for osmoregulation and as well as buffering capacity at all for maintaining a stable pH (rainwater tends towards the acid side on the pH scale) which will result in a rollercoaster pH in the aquarium.
Please note that the pH scale is logarithmic meaning a 1 point change up or down is equal to a tenfold increase in acidity/alkalinity.
Reference: Aquarium Chemistry; pH

Softened Water; Home/Office Water Softeners Use:

Home (or office) water softeners that employ salt should NOT be used for supplying aquarium water, as these strip most important minerals all the while increasing sodium to very high and out of balance levels (sodium is only required in trace amounts for most fish). The sodium that is present continues to strip ESSENTIAL calcium and other mineral ions.
This can severely affect osmoregulation in fish, especially many fish such as Loaches that normally prefer more soft water.
However these same softwater fish do not prefer soft water containing an unbalanced mineral content that is high in sodium but missing other essential mineral ions, which water from a home softener would be, regardless of whether you add back minerals such as the use of a Wonder shell or not!

The use of soft water from sources that utilize sodium OR EVEN from aquarium conditioners that have sodium bases is that the sodium often drives out the essential mineral cations.
The proof is the ability to maintain a good KH, however an un-naturally low GH often results.
One such test I conducted showed a KH of 200 ppm while the GH was only 20 ppm.

A review of Aquarium Water Conditioners:
Aquarium Conditioners, Information

The result is nearly NON-existent ESSENTIAL calcium, magnesium, and other positive mineral ions.
This can have severe affects on all fish, but is an ESPECIALLY noteworthy problem in Goldfish, Livebearers, and Rift Lake Cichlids!!

Another aspect is that softened water contains enough sodium to actually irritate a fish' epidermis, which in particular is harsh for scaleless or smooth scale fish (such as Loaches, many Catfish, Eels, Elephant Nose, and Ghost Knife Fish).

Although likely obvious to most saltwater aquarium keepers, the use of water softener water should NEVER be used for mixing saltwater or topping off a marine aquarium for evaporation.

See also:
Tap water for my Aquarium or Pond; Sodium

Necessary Minerals

From Original Article:
Do Fish Drink; Osmoregulation in Fish

Here are a few necessary TRACE elements/minerals (electrolytes) and their function.

• Calcium (Actually needed in more than trace amounts): Calcium helps to transport ions (electrically charged particles) across the membrane, is essential for muscle contraction, calcium assists in maintaining all cells and connective tissues in the body, and much more.
  Please read for more about Calcium:
  Aquarium Chemistry; Calcium
• Sodium (Actually needed in more than trace amounts which is why water from home water softeners should NOT be used): Regulates extra-cellular electrolyte, essential for the transport of nutrients across the cell membranes.
• Potassium: Regulates intracellular osmotic pressure, cell membrane potential, and salt excretion.
• Phosphorus: Energy metabolism.
• Molybdenum: Important for proper skeletal growth (very important in reef aquariums for hard coral growth).
• Manganese: Aids enzymes involved in metabolism, growth and maintenance of bone and cartilage.
• Iron: Oxygen transport in blood and muscle tissue.
• Magnesium: As stated previously, magnesium plays a role in the activity of more than 325 enzymes and aids in the proper assimilation of Calcium.
• Sulfates: Also as stated above, improve nutrient absorption and toxin elimination.
• Chromium: Important for proper utilization of sugars.
• Cobalt: Necessary for Folic Acid synthesis.
• Copper (very trace amounts): Co-enzyme for energy metabolism, aids in the protection of the myelin sheath around the nerves, important for iron absorption and utilization.

For a related post that deals with trace elements:
“Plaster in Paris in Aquariums and Ponds”

It is important to have a proper Redox Potential which describes the ability for the loss of an electron by a molecule, atom or ion to the gain of an electron by another molecule, atom or ion.
Without this reducing Redox Potential many minerals cannot be absorbed and properly assimilated. So it is very important to keep a “positively charged” aquarium or a Balanced Redox Potential via proper dissolved oxygen levels, calcium and other electrolytes, proper cleaning procedures and water changes (UV Sterilization can help too).

For more information about the Redox Potential, please see this article:
*The Redox Potential in Aquariums (& Ponds) and how it relates to proper aquatic health

For further reading on this subject, here are a few articles I recommend:

This one is great Understanding Water Hardness

A little hard to follow (pdf), but good reading:
Interactions of pH, Carbon Dioxide, Alkalinity and Hardness in Fish Ponds

This other Aquarium Answers article is an excellent compliment:
Tap water for my Aquarium or Pond? From Chlorine and Chloramines to Phosphates & TDS

For more aquarium information, please visit this site:
*“AQUARIUM AND POND INFORMATION”

*Sodium Ions: http://www.elmhurst.edu/~chm/vchembook/142Aposion.html

*A Comparison of Cellulose Acetate and FILMTEC FT30 Membranes

Carl Strohmeyer- Copyright 2016


Other Recommended Reference & Product Sites


Aquarium Information and Resources (Pond too)


*UV Sterilization, Sterilizer Use
The above article is the most in depth and constantly researched/updated article to be found ANYWHERE on the Internet!


TMC Total Dissolved Solids Monitor

An excellent stand alone product for testing your TDS from Tap, well, or even aquarium water.
A must have for any advanced aquarium keeper.



*Ich; Lifecycle, Identification, Treatment, Prevention



AquaRay Ultra Premium Aquarium LED Lights
Highest in PUR, The ONLY LED with an IP67 rating or higher for water proofing along with a full 5 year warranty to back them up! Why purchase brands without this rating such as the Finnex, Current, or Fluval only to be essentially placing an electronic light emitting device over your humid aquarium with little or no guarantee? In the long term, you WILL PAT MORE!



*Pond Care

*Aquarium Forum; Everything Aquatic&Aquarium Forum Board

*FISH AS PETS
Fish as Pets contains articles and commentary of Interest to the Aquarium Hobby


API/Rena Filstar High Performance Canister Filters & Parts
Premium Canister Aquarium Filters