What is so important about water hardness?

[Jan Cavalieri]

Before I started my first aquarium I did about 2 months of research - mainly reading books. My needs were simple I wanted a peaceful community tank. But it's not all about the fish.

Anyway - all the books and online articles had extensive information on how to cycle your tank so I was quite clear on that but not one of them mentioned water hardness. Even PH was barely mentioned.

So why is water hardness and PH some of the first questions asked to somebody that posts on these forums when none of the reading material think Water hardness is particularly important in freshwater tanks.? My test kit measures everything but water hardness. I checked the City's water analysis and they say our PH is 6.8-8 depending on the area of town. When I test PH I have found it is likely over 10 - because it doesn't match any of the colors on my test kit (which only goes to 9.9) After about 200 drops of PHdown I was able to lower the PH of my water to 7.0 - 7.2 (I have to deal with this after every water change so I try to make them small and frequent so I don't have to alter the PH as much now that I have fish in the tank). The City also mentioned that in some areas of town our water is on the acidic side crazy. All of our water comes from the Kansas river so I'm a little puzzled about the city report on water hardness and ph.

Water hardness is reported to be "9 grains per gallon" and they say the normal average hardness of water is between 6 and 12 grains per gallon- not a unit of measure I'm familiar with. But given how off they were on PH, I wonder how accurate it is. I know hardness has to do with the amount of mineral content in the water, but other than adding a water softener I'm not sure how critical it is. I know our city has hard water due to the frequent buildup of minerals on every faucet in my house - all hard like concrete. You literally have to chip it off with a hammer and flat edged screwdriver. In my fish tank it's only noticeable when the water evaporates and you see the amount of mineral content left behind.

So my question is - why is there a big fuss here about water hardness when it's not mentioned in any of the literature I've read for freshwater tanks? I do use a water softener product (I just follow their dosing recommendations since I haven't purchased a test kit yet for it) - fish all seem OK, I just have to scrub the tank a little more at the evaporation line to get rid of all those mineral deposits.

 

[Colin_T]

pH is the measurement used to tell us if something is an acid, neutral or alkaline/ base. Pure distilled water has a no mineral content and a pH of 7.0 and is considered neutral.

If something breaks down in pure water the pH drops and becomes acidic (pH goes below 7.0).
If minerals are added to pure water the pH goes up and becomes basic or alkaline (pH goes above 7.0).

Carbonate Hardness (KH) is the measurement of carbonates and bicarbonates in the water. These normally increase the pH. When there are acids in the water, the acids cause the pH to drop. If there are plenty of carbonates/ bicarbonates in the water, they neutralise the acids and help stop the pH from dropping.

General Hardness (GH) is the measurement of minerals in the water and usually measures calcium and magnesium chlorides. The more calcium and or magnesium chlorides in the water, the harder it is.

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If you have hard water, it contains lots of minerals and it usually contains lots of carbonates and bicarbonates. To lower the hardness, you dilute the hard water with soft water. Reverse osmosis (r/o) water, distilled water and rain water have no minerals and is very soft water. Mixing some of this soft water with the hard water will reduce the GH, KH and pH of the hard water.

If you want to reduce the pH, you can add small amounts of acidic substances like carbon dioxide (CO2), peat moss, drift wood and things like sodium biphosphate to lower the pH. These acids get neutralised by the carbonates/ bicarbonates and when the carbonates and bicarbonates have been used up, the pH drops.

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To increase the GH you add minerals like calcium and magnesium chloride.
To increase the KH you add carbonates and bicarbonates (baking soda is sodium bicarbonate).
When you add carbonates & bicarbonates the pH will go up.

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Fish have evolved to live in various water ways. Some fish live in hard alkaline water with lots of minerals and salt, eg: marine fish.
Some fish live in hard alkaline water without salt, eg: African Rift Lake cichlids.
Some fish live in soft acid water, eg: South American tetras, angelfish, Corydoras, etc.

Fish have been living in these waterways for thousands or even millions of years. Most marine fish look the same now as their fossilised ancestors found in rocks that are millions of years old. Australian and New Guinea rainbowfish have evolved since the last ice age 10,000 years ago and are considered quite new from an evolutionary point of view.

Fish have evolved different bodily functions to deal with salt, lots of minerals, or no minerals. If you put fish that naturally live in hard alkaline water into soft acid water, or fish from soft acid water into hard alkaline water, their body won't function as well as it should, and the fish usually dies within a short period of time.

The main difference between salt water, brackish water and pure fresh water fish is kidney size and the ability to osmoregulate their body. Marine fish have bigger kidneys and can expel large amounts of salt from their system. Fishes from soft acid water have smaller kidneys and cannot process salt or minerals as easily. Subsequently these soft water fishes have more problems if they are put into hard water or exposed to high levels of salt.

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Even though most domesticated aquarium fish have been bred in captivity for 20-50 years, they still retain their basic bodily functions and still struggle when put into water that is different to what they evolved in. Domestic aquarium fish have changed to some degree and can tolerate different conditions to what they evolved in, but we are talking about 20-50 generations of captive breeding vs 10,000+ generations of natural evolution.

Most tetras are still bred in soft acid water. Most livebearers are still kept in hard or brackish water.

Domestic tetras might live for 6-12 months in hard alkaline water and livebearers might live for 6 months in soft acid water. However, surviving for a short period of time is not the same as living a long healthy life.

I ask what the pH and GH are so I can suggest fish that are more suited to that particular water source. If people want to make up special water for soft water fishes or hard water fishes, that is fine and I can revise my suggested list. But most people simply want to fill their tank with tap water and keep fish.

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For the OP, if your tap water has a pH of 10, there is something wrong with your water supply and nobody should be drinking it. You need to get a decent pH, GH and KH test kit and find out exactly what your water is. Test kits can be expensive and most pet shops test water so it is usually cheaper to get a pet shop to test the GH and KH a couple of times a year. And you monitor the pH yourself.

Take a glass full of tap water and the tank water to the local pet shop and get them to check the pH, GH and KH. Write the results down in numbers when they do the test. Find out what the GH and KH tests are measured in.

I have never heard of the test results from your water company either so I would just get the water tested at a pet shop or pay a private company to test it for you.

Water softeners can cause problems and usually replace calcium with sodium. Depending on what fish you have, you might be better off making distilled water or using a reverse osmosis unit.

 

[Essjay]

9 grains per gallon converts to 8.6 dH and 154 ppm. The range 6 to 12 grains per gallon converts to 5.7 dH/103 ppm to 11.5 dH/205 ppm.

This https://www.cactus2000.de/uk/unit/masswas.php is very useful for converting hardness units.

 

[Byron]

Colin covered this issue very well. I will just pick up one aspect you mentioned that wasn't, directly, and that is using chemicals/additives to lower pH. Never use these if there are or will be fish in the aquarium. The pH is as Colin indicated tied to the GH and KH, and without first adjusting those the pH will simply return to its initial level after a temporary decrease, and this is even harder on fish.

Sometimes it helps our understanding if we have more than one explanation that may say the same thing a bit differently, and since I wrote an article on this a few years ago for another site, I will simply cut/paste it here. I will do this in two or three posts as it will be too lengthy otherwise.

Water Hardness and pH in the Freshwater Aquarium

Water in its pure form does not exist in nature; it is a powerful solvent, meaning a substance that easily dissolves other substances to create a solution. As rain falls, it picks up many gasses and particulate matter, and it continues to do this as it passes through the ground. Natural water values therefore vary with respect to hardness and pH because the water acquires specific properties from the landscape. Water flowing over or through rock will assimilate minerals from the rock, becoming what we term “hard” water. Water flowing through soils that contain organic matter will be “soft” because the organics bind with and thus remove minerals while creating acids that enter the water. The pH is largely the result of the hardness as well as the amount of carbon dioxide dissolved in the water.

As each freshwater fish species has evolved over thousands of years, their physiology has adjusted to the water values that occur in their respective habitat. We refer to these values as water parameters, and they include hardness, pH and temperature; each of these has an impact on fish. While many fish species appear to be somewhat adaptable, their physiology can be negatively affected if the parameters are outside the fish’s natural preference. Providing suitable water parameters in the aquarium is therefore an important aspect of providing an environment that is less stressful—and this directly relates to healthier fish.

Total Dissolved Solids [TDS] is the measure of all inorganic and organic substances in suspended form in the water. This includes the minerals salts. "Salts" here refers not solely to our common salt (sodium) but to various mineral salts, the most prevalent of which are chlorides, bicarbonates, carbonates, and sulphates of calcium, sodium, magnesium and potassium. Fish are directly impacted by TDS. In fact, when we speak of soft water fish, we are actually referring to the very low, sometimes near zero, level of TDS in their water.

Water hardness is the measure of dissolved mineral salts in the water, a portion of the TDS (total dissolved solids). There are two basic types of hardness of importance to aquarists, termed general hardness (abbreviated GH) and carbonate hardness (abbreviated KH, from the German “karbon” [carbon]). The combined GH and KH is sometimes termed “total hardness,” but this is of less importance because the GH and KH individually impact the water in different ways.

General Hardness is determined primarily by the minerals calcium and magnesium; GH is sometimes referred to as “permanent hardness” because it cannot be removed from water by boiling as can KH. GH is measured in several different units, but in the hobby the most common are parts per million (ppm) and degrees (dH or dGH). One dGH equals 10 milligrams of calcium or magnesium oxide per litre [1], and is equivalent to 17.848 ppm. Multiplying dGH by 17.9 gives ppm, and similarly dividing ppm by 17.9 gives dGH [the same formula works for KH]. The following chart equates the degrees and relative ppm to common terms in the hobby.

0 - 4 dGH 0 - 70 ppm very soft
4 - 8 dGH 70 - 140 ppm soft
8 - 12 dGH 140 - 210 ppm medium hard
12 - 18 dGH 210 - 320 ppm fairly hard
18 - 30 dGH 320 - 530 ppm hard
over 30 dGH over 530 ppm very hard

Fish are directly impacted by GH and TDS; their growth, the transfer of nutrients and waste products through cell membranes, spawning (sperm transfer, egg fertility or hatching), and the proper functioning of internal organs such as the kidneys can all be affected.

 

[Byron]

Post 2 on GH/KH/pH

Carbonate hardness is the measure of carbonate and bicarbonate ions; carbonates and bicarbonates are the salts of carbonic acid. It is sometimes referred to as Alkalinity [not to be confused with alkaline as in pH, something very different]. Carbonate hardness is also measured most often in either degrees (dKH) or parts per million (ppm), and the same formula to convert dGH to ppm and reverse also works for KH. KH is normally tied to the GH, since carbonate minerals include limestone, dolomite, calcium and calcite. Mollusc shells and coral are primarily calcium. Carbonate hardness is sometimes called “temporary hardness” because it can be removed from water by boiling which precipitates out the carbonates.

KH has some direct impact on fish; but it also “buffers” the pH by binding to additions of acids or bases, keeping the pH stable—or more correctly, preventing it from changing—and the higher the KH, the greater the buffering capacity. A simple way is to think of the buffer as a sponge that soaks up the acid being added; however, at some point it will become saturated, and further additions of the acid can then cause a sudden and very large fluctuation which is usually fatal to the fish. This buffering is why attempts to adjust (lower) the pH of hard water are dangerous and will fail unless the KH is first reduced.

pH stands for pondus hydrogeni, Latin for “potential of hydrogen.” Water is made up of positively-charged hydrogen ions and negatively-charged hydroxyl ions, and pH is the measurement of the ratio of hydrogen and hydroxyl ions in a body of water. Acidic water contains more hydrogen ions, and basic (alkaline) water more hydroxyl ions; neutral water has an equal proportion. The pH is closely linked with the level of carbon dioxide (CO2) because CO2 produces carbonic acid. The hardness also impacts pH, since the carbonates bind to acids as they appear; as mentioned previously, this buffering will prevent or limit changes in pH.

The pH is measured with a scale from 1 to 14 with 7 being neutral. Numbers below 7 indicate acidic water, increasingly more acidic as they lower, while numbers above 7 indicate basic or alkaline water, increasingly as the numbers rise. This scale is logarithmic, meaning that each unit is a ten-fold increase/decrease; so a pH of 5 is ten times more acidic than a pH of 6, and 100 times more acidic than a pH of 7, and a thousand times more acidic than a pH of 8. Fish must never be exposed to sudden pH changes approaching one unit, as this is very stressful and may kill some species.

The impact of pH on fish is significant; water constantly enters the fish via osmosis through the cells, and the pH of the water can shift the pH of the fish’s blood if they are different. The fish must therefore regulate its internal pH accordingly, and this takes energy. Fish do this regularly in nature in response to changes in its environment, but these are usually minimal. Some fish species have a wider range of tolerance than others, for reasons that are not certain.[2] Fish that are wild caught show intolerance for hardness and pH levels that are not close to their origins. Maintaining a species in water that is reasonably close to its natural habitat is usually advisable.

 

[Byron]

Post 3 (final) on GH/KH/pH

Adjusting water hardness and/or pH should only be done by natural means, never with chemicals and preparations because these will often be “blocked” by the initial KH and may have or lead to other effects that can be highly detrimental to fish and bacteria. Water should always be prepared outside the aquarium and then used to gradually replace the aquarium water over a period of time to avoid shock to the fish.

Hard water can be made softer by diluting it; Reverse Osmosis (RO) water, distilled water, and rainwater can be used. Water will soften in proportion to the dilution; mixing hard tap water half and half with one of the afore-mentioned waters will result in water that is half the original hardness. A caution on home water softeners: many of these work by replacing the calcium [Ca] and magnesium [Mg] ions with sodium (=common salt) [Na] ions. Each Ca and Mg ion is exchanged for two Na ions. Therefore, the end result is water containing twice the ions--or double the total dissolved solids--it previously had, and for soft water fish this is an even worse situation, plus there is the detrimental impact of the sodium (salt).

Soft water can be made harder by using calcareous substances in the filter (preferably) or the substrate. Dolomite is the best, since it is composed of both calcium and magnesium. Crushed coral, marble and limestone also work but need to be in crushed form (gravel, sand) to have more of an effect. If these latter are used, magnesium can be added with Magnesium Sulphate [pure Epsom Salt] at each water change; very little is needed. The amount required can vary depending upon the softness of the original water, but in general, very little calcareous material is required.

Adjusting pH should not be attempted except in conjunction with altering the GH and KH, since these are closely related. Most municipal water supplies will be medium hard to hard with a correspondingly higher pH in the basic range (7-9). It would not normally be necessary to raise this further, but if the tap water range is medium hard with a pH in the 7’s, adding a calcium or magnesium base to increase both the GH and KH will naturally result in a higher pH, as one might do for rift lake cichlids.

The GH and KH will remain steady once adjusted, provided no substances to increase it are present in the aquarium. Once the KH is low, the pH will naturally lower due to the carbonic acid being added to the water from natural biological processes such as fish and plant respiration, bacteria through the breakdown of organics such as fish waste, uneaten food, plant matter, etc. Regular partial water changes using either similarly-prepared water or even tap water [in smaller amounts] should not overly impact the hardness and pH if the tank is biologically stable.

A final comment on using baking soda (sodium bicarbonate) to raise pH. This can be useful in an emergency, but should not be used long-term. Sodium bicarbonate has no effective buffer action and cannot stabilize pH when additional acids are being produced such as by waste products. Further, the sodium ions will eventually reach levels that are intolerable for soft water fish (Weitzman et al. 1996). Commercial preparations such as rift lake mineral salts and others are effective though they are very expensive long term or in larger aquaria.

Footnotes:

[1] Baensch & Riehl (1987), p. 29.
[2] Muha (2006), p. 68

References:

Baensch, Hans A. and Rudiger Riehl (1987), Aquarium Atlas, Volume 1, First English Edition.

Ghadially, Feroze N. (1969), Advanced Aquarist Guide, The Pet Library Ltd.

Hiscock, Peter (2003), Encyclopedia of Aquarium Plants, Interpet Publishing, First Edition for the United States and Canada by Barron’s Educational Series, Inc.

Hiscock, Peter (2003), Aquarium Designs Inspired By Nature, Interpet Publishing, First Edition for the United States and Canada by Barron’s Educational Series, Inc.

Muha, Laura (2006), “The Skeptical Fishkeeper,” Tropical Fish Hobbyist, April 2006, pp. 66-69.

Weitzman, Stanley H., Lisa Palmer, Naercio A. Menezes and John R. Burns (1996), "Maintaining Environmental Conditions Suitable for Tropical and Subtropical Forest-adapted Fishes, Especially the Species of Mimagoniates," Tropical Fish Hobbyist, Volume 44, No. 11, June 1996 (Part One), pp. 184-194 and July 1996 (Part Two), pp. 196-201.

 

[FishGuest5123]

You know that question is a good one. On another forum, they always want to know ammonia, nitrite, and nitrate. Occasionally they will ask for PH. Very, very rarely do they ask for Gh/KH. I think it depends on the forum and what the members are accustomed to. The other forum is big on using salt and meds when needed. They have an entirely different approach to things but are a very reputable site. Sometimes I think it depends on where the members are from. The US has more access to meds so they use them more. The UK and Australia are less aggressive with antibiotics because they aren’t easy to get. You have to work with what’s available and various water supplies. Sometimes I have to remember what site I’m on before replying to a question. Lol!

 

[Jan Cavalieri]

Very interesting. Now you have me concerned about the 10 PH in our water here in Topeka - I actually dug through their website to find some older reports and found a couple of years where they said the PH of our water was 10.4 - then suddenly this year they report it as lower. Both my daughter and I have tested it for our aquariums and found it to be over 10. I know I adjusted the pH of my fish water with a product called PHdown (with the "down" actually being a down arrow). The tank was done cycling and there were no fish in the tank. My daughter has a nano tank that she also likely adjusted the PH before she got her guppies (she has a nano tank) I thought it was a bit unusual to have to use the whole bottle to get our PH to a 7 (I believe all my fish can tolerate a PH of 6-8). Again, PH is sometimes mentioned in the begginners fish books but they don't tell you what to do about it. Me, being American and a straight A student in all my chemistry classes in colleges) tend to think it's "Better living through chemistry". Once I've also altered the PH with fish in it but thought later it really wasn't that high - it had drifted to 7.4. Got it back to 7.0 with about 25 drops - the fish don't seem to notice. I also add all the Seachem products like Prime, Pristine, Stability etc to their water daily (as written on the bottle) - always try to do it somewhere where the fist aren't but they are the most curious little animals I've every seen. I use a Phython to do water changes, which - according to them - you either put all your extra "solutions" in the tank water before you do a water change or after - whichever is my preference. The way you guys describe it I risk killing my fish when I do this. I am severely disabled with COPD and live on O2 - I rarely even leave the house because I also have narcolepsy and could (and have) fallen asleep while driving (for 15 yrs they've been telling me I only have "about 5 more years to live", obviously fewer if I crash the car.) Any way, One of the reasons I even considered getting a fish tank was that I had read you could now do water changes without carrying heavy buckets around - the product being the Python. Of course with the Python you hook one end to your faucet and put the cleaning/siphoning end in the fish tank.(no buckets) That makes it impossible to make any adjustments except before or after the water change. Now due to my disability I cannot do a lot of walking, especially while carrying something - but I guess I may have to. So it will just take me a couple of hours now - no big deal as long as I'm allowed a nap afterwards Then I could use all my chemicals on each bucket (my buckets are not 5 gallons - I cannot lift over 2 gallons without spilling water out of it. I feel MUCH better now.

Not sure what I'm going to do I am concerned now about our real water hardness since the City is reporting a much more acidic PH than what my daughter and I have found. I wonder how accurate the hardness is - since even though all Topeka citizens have evidence of hard water on all their plumbing - they only register as "moderately hard" per Byron's conversion of the City report of water hardness. I guess I will have to get a water sample analyzed by a pet store or chemist. Thanks for the in depth explanation of water hardness (I understand PH fairly well and was aware of it's interaction with hardness but didn't realize how extensive it is! ). Of course in chemistry class you always use distilled water so we didn't have any discussions about this.

So what would you guys do if you found you had hard water and a high PH? Would you really use distilled water (I assume just to lower it, not for ALL the water - which I believe that due to osmosis, it would be a very bad thing for living creatures to drink) I'm not familiar with the mineral content left after using Reverse Osmosis systems but I know you can purchase them for your house, or make your own.

 

[Colin_T]

Reverse Osmosis units should theoretically remove 99% of the minerals in the water. However, there is some variation in that and some units remove 80% and others remove 99%. Most fit somewhere in between.

If I had tapwater with a pH of 10, I would be concerned about my skin peeling off when I have a shower. Bleach (used to clean things) has a pH around 12 and that dissolves anything organic. African cichlids from Lake Tanganyika live in water with a pH around 8.2-9.0. No other fish lives in water with a higher pH. Even seawater only has a pH of 8.5.

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I would make a solar still and mix that with tap water to get a usable GH and pH. You can make a solar still out of a plastic storage container, a bucket and a couple of rocks or bags of gravel.

You put a clean rock in the bucket.
Put the bucket in the middle of the plastic storage container.
Put the storage container out in the sun and half fill it with tap water.
Put the lid on the storage container and put another rock on top of the lid in the middle of the lid.

The water evaporates and collects on the underside of the lid. The rock on the lid causes the lid to sag and the condensation on the lid, runs towards the centre and drips into the bucket. The water dripping into the bucket is pure water with 0 GH and a pH of 7.0. Mix this water with the tap water to make something usable.

 

[Jan Cavalieri]

Interesting idea but I don't know if I'd ever try do. That's a lot of work for as often as I change the water. As far as the pH - yes - I'm surprised as well - could also be the test kits my daughter and I are using tend to test high too. But I've never had a test that color matched anything on the chart and when I pour my (adjusted) aquarium water that I test down the drain it immediately turns dark blue as soon as the test kit water (a nice light blue) hits our tap water. I would say a large number of people in our city drink filtered or bottled water. Until a couple of years ago we had a "red water" problem where every once in a while everybody in a certain area of town would have red water - you'd have to wash all of your clothes again hoping the water was out of your pipes - just iron leaching into the old pipes. Since they fixed it my skin is so horribly dry if I didn''t cover it with moisturizer it would itch like crazy after taking a shower. But since the scale is logarithmic a ph of 12 (bleach) is significantly higher than ours. I'm itching thinking about it!

I did a 50% water change yesterday (after removing huge amounts of trash with my turkey baster) because with the addition of all the new fish suddenly everything was higher. - I then took about 1/2 gallon of their water and mixed in all those seachem solutions they want you to add - along with some PH down since the PH was nearly 8. PH is back to 7 but nothing else changed much but my nitrates did drop to half of what they were- I feel like I'm cycling the tank all over again - and I may be. I located all the fish and nobody has died thankfully.

 

[seangee]

Hardness and pH are both (usually) fairly stable from a water supply. I would collect some in a clean jar and take it along to a fish shop to test. You can spend the money on decent test kit but these parameters don't typically change over time. If it is unsuitable it is useful to know your starting point.

Options are:

1. Filter your source water - this can be expensive and is time consuming. You may filter all of it or mix the filtered water with tap water to get a good result. I have done this in the past. I stopped because of the nuisance value and having to keep track of which water was in which container (and which tank it was intended for.
   
2. Buy RO water and mix it with your tap water to get the right ratio. I also used to do this but stopped because of the hassle of taking my car to collect 100 litres of water per week. I also still had to filter the tap water I mixed it with because our supply has a crazy high level of nitrates.
3. Use RO water and add the minerals back. This is what I am doing at the moment. I ended up buying an RO unit for convenience, although it may actually be cheaper to just buy the RO (our water is metered and RO produces a lot of waste).

Don't be fooled by the so called re-mineralising filters that you can add on to an RO filter. They produce very inconsistent results. Either buy a suitable mix or make your own. Again for the sake of convenience I just buy as that way I know that every drop that goes into the tanks is the same.

FWIW pH is not actually that important. Most fish can tolerate a fairly wide range (but do check for the species you keep). Its more important that it is stable. If you get the GH and KH to a suitable level chances are the pH will be acceptable.