Safe Water Sources for our Planted Aquarium
After we discussed what water parameters make for ‘good’ water for our planted aquarium, it makes sense to discuss where we can get that ‘good water.’ So in this article, we will discuss the safe water sources that we can use for our planted aquariums.
From the composition of the water, how it is produced or created, are there any pros and cons for each? Understanding your water is a critical part of this hobby. We already discussed in-part some of these water sources from previous articles, and we will review them here and additional safe water sources to give you a wide array of choices.
Table of Contents
Types of Water
Reverse Osmosis (RO) Water
De-Ionized (DI) Water
RO vs Distilled vs DI Water
What About Rainwater?
When Not to Use RO/DI, Distilled, or Purified Water in Our Planted Aquariums?
How to Remineralize RO/DI, Distilled, or Purified Water?
When to Use RO/DI, Distilled, or Purified Water in Our Planted Aquariums?
Your water source should be chlorine or chloramine free at the most basic of things and should have very little unknowns in it. Remember, you cannot test everything in the water, so your water must be clean with little unknown substances. But to add to the confusion, very pure/clean water is also bad to your plants and faunas, which we will explain below.
The known things you add to your planted aquarium like fertilizers, fish food and vitamins, KH and GH Boosters, rocks/stones (may add to your water hardness if not inert), and natural by-products from the Nitrogen Cycle such as acids (from injecting co2, substrate, breakdown of wastes, Ammonia, Nitrites, and Nitrates, Phosphates, etc.) all add up to your water composition.
Water Drop on Grass After a Rain
But at least you know what you are adding, you can test most of this too, and you can control the dosage, or how much you feed your fish (do not overfeed), and you can certainly control how many fish you add (do not overstock) so you can prevent substances from dangerously accumulating in your tank.
But first, let me discuss to you what is Osmosis and Osmoregulation and how they relate to the quality of our water source.
Osmosis is the process in which any solvent moves through a membrane in a direction from lower concentration to higher concentration that tends to equalize the solutes’ concentration on both sides.
This is due to osmotic pressure and is used by every living thing to regulate their cell solute concentrations within safe levels (osmoregulation). For example, if you put a freshwater fish in pure water free of any minerals and other salts like a distilled water, this means that the fish cells are much saltier than the water. The water forces its way in the fish due to osmotic pressure (lower concentrations to higher concentrations) and quickly dissolves the salts in the fish’s body. The fish cell will continually swell, and under such conditions, the fish cell may bursts, dead fish.
So what if the freshwater fish is put in water with very high solutes than the water in its cells (in the case of salt-water or water with very high dissolved solutes – TDS/Hardness/Salts)? The fish will continually lose its water within its body (water goes from lower concentrations to high concentrations). As a result of this, the fish will try to swallow a lot of water and through its gills to compensate. But the osmotic pressure may be too much, and the fish could not adapt faster than it is losing water until its cells shriveled another dead fish.
Plant cells are protected from bursting by the rigid cell wall which surrounds the cell membrane. As water enters, the cell expands until it pushes up tight against its cell wall. The cell wall pushes back with equal pressure so that no more water can enter.
But plants cannot thrive in spotless water due to the absence of the nutrients needed to create their own food.
How does Osmosis relate to the quality of water we used? It turns out, faunas and plants don’t only need pure H2O molecules. They also need salts (carbonates), minerals (calcium, magnesium, iron), etc. Present in the water but also not too much.
Most of the water purification processes used today remove 90 to 99% of all contaminants in the water, and these needed salts and minerals. Hence, we have to re-mineralize these purified waters before using them in our planted aquariums.
Types of Water
Reverse Osmosis (RO) Water
This is a type of water that has been filtered by a semi-permeable membrane and other filters to remove ions, unwanted molecules, and larger particles. This membrane removes 90 to 99 percent of the water’s impurities, depending on the quality of the RO water filtration unit. Unfortunately, among the molecules that it removes are the minerals that benefit our faunas and plants.
Remember the direction of Osmosis we explained above (water or any solvent moves from a low concentration of solute to a higher concentration through a membrane to equalize the concentration of the solutes on both sides). For this to work in reverse, pressure is applied to exceed the osmotic pressure, so the solvent (which is the water) moves to pass the membrane in the opposite direction.
The membrane will trap larger molecules (even bacteria), Nitrites, Nitrates, even the salts, minerals needed by our plants, and faunas while allowing the smaller H2O molecules to pass. Activated carbon, which is commonly included in RO filtration units, will remove chlorine, and with enough staying-time, it removes chloramine effectively. But if the chloramine is subjected to an oxidation-reduction reaction, chlorine is removed, but Ammonia will stay. Remember, Chloramine = Chlorine + Ammonia.
But if the RO unit has a post-filter cartridge containing standard water softener resin, this can remove the Ammonia left behind. Reverse Osmosis systems remove the hardness and reduce the pH (usually pH is about 6.5 after RO and a KH of zero). The Ammonia will exist more as Ammonium, which can be readily removed by standard cation (water softener) resin – DI units, which we will discuss further below).
Here are the contaminants removed by household reverse osmosis units (this is not an exhaustive list that an RO unit may remove):
- Particles like Asbestos and Cysts
- Pesticides – Endrin, Heptachlor, Pentachloropenol, Lindane, Atrazine*, 1, 2, 4-trichlorobenzene*
- Ions and Metals – Copper, Fluoride, Iron, Lead, Chromium, Chlorine*, Magnesium, Manganese, Calcium, Cadmium, Barium, Arsenic, Aluminum, Mercury, Potassium, Radium, Radon, Sodium, Sulfate, Zinc, Selenium, Silver
- Organic Chemicals – (Ammonia, Ammonium, Nitrites, Nitrate these may not be totally removed at all unless RO unit is combined with a DI unit), Toluene*, Dichlorobenzene*, Carbon Tetrachloride*, Benzene*, Trichloroethylene*, Total Trihalomethanes (THM’s)*
* Activated Carbon, if included in an RO system, can treat these contaminants, which usually is.
After pre-treatment with an RO unit, Ammonia will be present more as Ammonium due to reduced hardness and decreased water pH. It can easily be removed by a post-filter cartridge containing standard water softener resin – DI unit.
This method of water purification is very cost-effective compared to distillation. It may set you back 100-200$ (lower-end of the price point) when starting up, but if you are using it for drinking water and your planted aquarium, then it will save you money in the long run.
Reverse Osmosis System 5 Stage
Distilled water is water that is subjected to the distillation process. It is boiled until it turns into water vapor and condensed back into liquid in a separate container. The contaminants/impurities from the original water that does not boil below the water’s boiling point are left behind in the original container.
It aims for a TDS of 0 ppm but the method and equipment used are not practical nor cost-effective for home used, much more for planted aquariums. While you can buy distilled water cheap per gallon, the cost will quickly add-up most, especially if you have many tanks or huge tanks.
Imagine this at your home
500 Liters per Hour Distilled Water Plant
Immediately after the distillation, it has a pH of 7.0, but after a few hours, it will absorb carbon dioxide from the atmosphere, and the pH will become acidic at 5.8. It has no minerals in it and is unstable by nature with 0 KH. It continues to absorb carbon dioxide until it comes into equilibrium with the atmosphere.
Although the distillation process may guarantee zero TDS, some volatile organic compounds and other volatile solvents with a low-boiling point than water (such as benzene) will also evaporate along with the water. So it does not really guarantee a lack of contaminants but remains one of the purest types of water.
It is the softest water after purification, usually chlorine-free (but distillation alone cannot remove chlorine, please see below), and it has 0 KH and 0 GH. Unfortunately, it has no minerals.
De-Ionized (DI) Water
De-ionized water has been treated to remove all ions, which means all of the dissolved mineral salts. Depending on the water source before purification, Distilled water is often purer than De-ionized water, but that doesn’t necessarily mean that it’s better, most especially if we are using it in our planted aquarium. There are pros and cons to using RO, Distilled, and DI water, particularly when it comes to cost and efficiency.
DI units use special resins that capture positively and negatively charged ions in the water. Organic materials and inorganic minerals are the most common impurities/contaminants in the water. Most of the organics part and rust, metals, particles, pesticides, etc., can be removed by complete RO units (usually 3-stages). After this pre-treatment, ions can still be present in the water and is sent into a DI system (RO/DI Systems 4-Stages and up).
Using RO-DI Water Aquascaped by Me
DI Systems have two types of resin: cation and anion. These two resins attract positive and negative ions, respectively, such as Ammonium, Nitrites, Nitrates, Chlorides, replacing them with H+ and OH-. H+ combined with OH- becomes H2O – water. This combination of RO and DI units can remove nearly all contaminants.
Complete RO systems usually have 3-4 Stages of Filtration, and complete RO/DI usually has 4 or more stages. Please consult the product specifications before buying them.
RO vs. Distilled vs. DI Water
To easily see the pros and cons of each water purification system, here is a table to help you decide which is better for your needs and applications and, most specifically, for our planted aquariums.
Reverse Osmosis (RO) Water
De-Ionize (DI) Water
This is any water subjected to some purification process, all the above-mentioned included, alone or in combination. Distilled water has been the oldest and most common form of purified water. Still, in recent years, there are more water purification processes such as Reverse Osmosis, De-ionization, Activated Carbon, Zeolite, or UV, etc.
These processes can be combined to produce water so pure that its trace contaminants are measured not in parts per million (ppm) but parts per billion (ppb) or parts per trillion (ppt).
Before we get further down below with other safe water sources that you can use with your planted aquarium/s, one of the benefits of using such Purified water sources like RO/DI and Distilled waters is you have little unknowns in the water. You control what you put in it and your water parameters (nutrients, KH, pH, GH, etc.). You have no excess or lack of anything once you nailed how you should remineralize it based on your water parameter goals.
Springwater or deep-well water comes from underground, constructed by digging or drilling to access groundwater in underground aquifers. The groundwater is drawn-up by a pump. At home, we still have a deep-well pump and a customized concrete rectangular pool for storage. This concrete pool is raised, so gravity creates the pressure to flow in the pipes. This is for emergency purposes in case the municipal tap water goes down.
Springwater greatly varies from one location to another, and there are many unknowns in the water that you simply cannot measure practically with a test kit. Adults can drink our well water but is a no-no for my baby, kids, pregnant wife, elders, etc. It has no chlorine, 0 Ammonia, 0 Nitrites, but it adds 20 ppm of Nitrates. Overall it has over 500 ppm of TDS (borrowed a TDS meter from a friend).
It is in hard water territory, over 15 dGH, maybe even more as I didn’t bother to finish the GH test. But I used our deep-well water for 2 years in my community tank, keeping non-fancy Goldfish, Mollies, and an Angel Fish with no issues, except maybe a couple of algae blooms, but the most annoying thing is the lime/calcium deposits in my aquarium glass and causing my filter’s impeller to stop after some time.
Again, no spring water is the same, and if you can drink it, it doesn’t mean it is safe for your planted aquarium. So we always recommend testing your deep-well water first for Ammonia, Nitrites, Nitrate, Phosphate, KH, GH, TDS, and pH for any fluctuations, etc., before using it. If these water parameters fluctuate too far, between water changes, we highly suggest considering another water source.
If your deep-well water is hard or too hard, you can dilute it with RO/DI or distilled water. Start with a 50:50 ratio and test the hardness (GH) again. If it is still hard water, you can try 25 % deep-well water and 75 % RO/DI water mix. Do this outside the tank.
This process of mixing different water sources doesn’t need re-mineralization since the deep-well water already contains vital minerals like calcium and magnesium. Calcium is essential for the neurological functioning of our faunas. On the other hand, magnesium is an important nutrient for the development of bones for our fish and is vital for biological functions.
It usually comes from an underground water source, bottled at the site, to avoid contamination by flowing into pipes or transporting into non-sterilized containers. The FDA restricts manufacturers from adding any further minerals to the product. Mineral water should at least contain 250 ppm TDS of trace minerals, according to the FDA. Those trace minerals include calcium, magnesium, potassium, sodium, bicarbonate, iron, zinc, and carbon dioxide.
CO2 helps prevent oxidation and prevents bacterial growth in mineral water.
Naturally, carbonated water gets its CO2 from the source (we call it ‘bukal’ in the Philippines), or the manufacturer can add food-grade CO2 after extraction. However, mineral water may undergo some treatment. This includes eliminating toxic substances and other contaminants. If the natural spring water has many contaminants, the manufacturer may pass the water into RO/DI systems, removing most contaminants and trace minerals. The manufacturer then remineralizes the water and add CO2.
It isn’t cost-effective to be used for our planted aquariums with all these processes, but it is actually safe with fewer unknowns.
Last but not least, Tap or Municipal water.
If you are sourcing your aquarium water from a commercial water system (tap water), that water should be treated to ensure it is safe for human consumption. The water is cleaned and filtered, then add chemicals to prevent anything harmful from developing in the water while traversing the pipes leading to our homes.
Most water treatment plants used chlorine to disinfect and kill all harmful organisms in the water. This small chlorine dose is safe for human consumption, but not for our faunas and beneficial bacteria.
The problems with chlorine are it is unstable and quickly dissipates from the water. This is why many hobbyists stock up on tap water and let the chlorine evaporate for several days to a week. So the water treatment plants add more chlorine to make sure that some will remain in the water as it reaches our homes.
Depending on your location, some water treatment plants have started to use chloramine to treat our water. Chloramine is the combination of chlorine and Ammonia (that’s no good). If you remember, Ammonia is bad for our faunas. So we are dealing with two harmful substances that we will use as our aquarium water for our planted aquarium.
However, from the water treatment plant’s perspective, chloramine is more stable than chlorine alone, and it will not easily evaporate from the water. It is more unlikely to combine with other chemicals too. But chloramine is less effective as a disinfectant than chlorine, so higher levels of chloramine are used.
Adding chlorine or chloramine into our water for human consumption is safe but can instantly kill the beneficial bacteria that you have long-established and keep our planted tank stable.
Using chlorinated water during a water change may result in cloudiness in the water afterward as a result of dead good bacteria or overproduction of Nitrosomonas bacteria (bacterial bloom) due to Ammonia spikes caused by the dead good bacteria not able to do their job and them being dead in the first place.
This will revert your cycle to zero or if you are lucky, will result in only a mini cycle. So take care of your beneficial bacteria by not drying them out or using a chlorine-free water source.
Once the correct number of Ammonia oxidizing bacteria (Nitrosomonas) colonize in your planted aquarium, the excess bacteria die and this is when the cloudiness of the water starts to clear.
We can use commercial dechlorinators like Seachem Prime, which can remove the chlorine instantly and detoxifies Ammonia, Nitrites, and Nitrates so your biological filter can effectively remove them. The API Tap Water Conditioner can remove chlorine instantly too and detoxifies heavy metals in our tap water. Still, it doesn’t specifically say that it can detoxify Ammonia, so only use API Tap Water Conditioner if you know that your water treatment facility is just using chlorine for water disinfection. Contact them.
Other hobbyists and friends stock the tap water for days to weeks before using for their water changes. This is for the chlorine to evaporate.
Here in Manila, Philippines, it is common to have around 100-200 ppm of TDS from our tap water. This is the baseline TDS before conditioning, as water conditioners also add to the TDS.
However, tap water traverses through pipes and may be contaminated in the process due to leaks. So it’s also important not only to condition it but test it for Ammonia, Nitrites, Nitrate, Phosphate, KH, GH, TDS, and pH for any fluctuations, etc. before using it. If these water parameters are fluctuating between testings, this is unstable water. Then we highly suggest considering another water source.
What About Rainwater?
Rainwater can be used for planted aquariums, but the method of collecting and your location are some of the concerns. The frequency of rain is one of the concerns, so you should always have a primary source of clean water for your planted aquarium. Another concern for rainwater is if you are living in an urban and industrialized area where rainwater can be subjected to the downwash of those pollutants in the air (vehicular/industrial pollution). But pure/clean rainwater is suitable for planted aquariums in general, and what applies to RO/DI or Distilled water can also be applied to rainwater. You should remineralize it first, or you can mix it with conditioned tap water to achieve the desired KH, pH, and GH.
- Roof ditches and roof gutters will collect any contaminants from debris, manures from animals, insects, rusts, impurities from roof materials/weather deterrent used, etc., so it is important to consider how you are collecting the rainwater. You can use water basins or blue plastic drums just for this purpose straight from the rain and not from your roof ditch or gutter. Cover your rainwater storage to avoid mosquitoes laying eggs.
- As always, test your rainwater before using it. This is so you can determine how much remineralization you need to add to be suitable for your planted aquarium and test to make sure there are no contaminants in the water (Ammonia, Nitrite, Nitrate, Phosphates, etc.).
- Don’t collect in the first 15 minutes of the downpour. Let the rain itself wash out possible contaminants from the air.
When Not to Use RO/DI, Distilled, or Purified Water In Our Planted Aquariums?
During water changes, do not use pure RO/DI, Distilled, or Purified Water without remineralizing it first. Your fish can be killed by Osmotic shock, and there is nothing to buffer the acids produced in your tank and during CO2 injection, causing your pH to swing wildly in a very short amount of time.
How to Remineralize RO/DI, Distilled, or Purified Water?
It is the KH and GH that you actually need to add when we say you need to remineralize one of these purified water before using it in our planted aquariums. Plant fertilizers can be added afterward. You should always have your test kit ready and purchased already.
Here are some of the scenarios:
- For example, I used deep-well water before, and I want to migrate into pure RO/DI water. The KH and GH in my planted tank were very high, +15 dH. In the next 3 weeks or so, I performed twice 25 % water change with pure RO (without remineralization). This is for the faunas to be able to adapt slowly and dilute the hardness and excess minerals. Unfortunately, 4 of my Kohaku Swordtails perished if I remember it correctly, and some Mountain Minnows, but all my Tetras, Platies, Mollies are fine. Eventually, I reached my target of 3 dkH and 3 dGH. It won’t go down, even with repeated water change, it turns out, the limestones in my tank gives off this hardness (calcium carbonate). Then I was back into my regular weekly water change, still with pure RO. I am adding + 1 dKH using baking soda if it goes down to 2 dKH due to CO2 injection when water change time. Remember KH depletes too. For an in-depth discussion about KH and GH, please go here.
- If you want to start from the beginning using RO/DI, for example – If you are still starting and setting up your first planted aquarium and plan to perform fishless cycling, that is the perfect time to establish your RO/DI’s KH and GH. There are many ways to add KH and GH to your water. Please see the below link.
For adding KH and/or GH in your water, please go here.
When to Use RO/DI, Distilled, or Purified Water In Our Planted Aquariums?
- Assuming that you remineralize already, you can use any of this purified water during water changes and even during start-up (after aquascaping and planting and you need to fill your tank with water).
- Assuming that you remineralize first every water change, you can use any of this when just topping off the water due to evaporation losses without remineralization. Why? Whatever water has evaporated, it did not take any minerals in it. The minerals remain in your aquarium. Just like when seawater evaporates, the salts remain.
- Without remineralizing, you can combine one of these purified water to lower/dilute the general hardness/TDS of your tap or deep-well water. For example, if you have tap water with a dGH of 10, mixing it with an RO/DI water 1:1 ratio will halve the GH to 5 dGH.
Using Mix of Tap Water and Purified Water Aquascaped by Matt Mendez Philippines
This article covered the types of water that we can use safely in our planted aquariums, where they come from and the processes involved in producing these pure waters.
From distillation, reverse osmosis, and De-ionized water, these water purification processes remove most of the impurities/contaminants. Combining them like RO/DI or RO to Distillation outputs very pure water. However, the effectiveness of these water purification systems still depends on the quality of the water source. We also discussed the pros and cons of each.
We also touched upon the topic of Osmosis and osmoregulation within living cells and its effects when using these very pure waters in our planted aquariums for our faunas and plants.
You can also use tap water or deep-well water for our planted aquarium provided that you conditioned it first and test the water’s parameters for any fluctuations before using it.
Finally, we discussed when to use and not to use RO/DI, Distilled, or Purified water and how to remineralize for it to be suitable in our planted aquariums.
I hope you enjoyed this article. If you have additional questions or want to share your experiences with the water sources you used in your planted aquarium, please leave a comment below. We hope this article helps you decide what should be the best water source you can use for your faunas and plants. Next, we will be discussing the different types of filtration and filters we can use in our planted aquariums.