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Water Conditioner







Using RO water or distilled water.





But my water is nice and clear, it must be good?

It may be surprising but its not fish that prefer clear water, its humans. Just because water looks clear doesn't mean it is right. To start with you should always use a water conditioner before adding water to the tank and then after that you need to take further care.

What's making it dirty? I cant see any poop in the water?

If you look back to the diagram above you can see at least three sources in the tank are contributing to ammonia levels, the fish, the food you feed them and any plant matter that is decaying. Ammonia is a pollutant in the tank, it is causing harm to the fish at even low levels. The fish will feel stressed and delicate tissue will be being attacked by the chemical. Ideally you should have an Ammonia reading of zero in tank or pond.

How can I tell what the Ammonia level is, I cant smell it?

Next time you go to your local fish store, go buy a test kit. Or if they offer the service take a sample of your water in with you for them to test. A test kit though is worth every penny invested, you should use it regularly to keep an eye on what is occurring in your tank. Ideally you need a kit that tests for Ammonia, Nitrite, Nitrate and pH. Most kits give you a reading in parts per million. The Ammonia reading should be 0 ppm, any reading above this is unwanted, and above 0.1 ppm requires immediate attention.

My reading is above 0ppm what do I do?

The easiest and simple solution is to do a water change. Treat the water with your dechlorinator, get it to a matching temperature with the water in the tank and then do a 25% change ( if your reading is 0.1>0.25 ppm) and a 50% change if its above that. You need to keep changing the water until the level reaches a safe limit. Avoid stressing the fish by changing too much in one go, or too regularly, create a regime until you can be sure the Ammonia level is 0 or  close.

I cant be expected to do this all the time can I?

Yes. You should perform weekly or fortnightly water changes on your tank. There are chemicals that will stop the ammonia being toxic that you can add to the tank, but really there is no substitute for good tank hygiene. When you get a tank to cycle the daily water changes are no longer necessary ( though weekly changes still are) , you have a bacterial culture removing the chemical for you.


Inside your filter you are aiming to create an environment that the bacteria will love. They are called nitrifying bacteria and eat ammonia/nitrite and produce a far more harmless chemical called nitrate. You need a filter in any tank you have, if not several, check the forum for advice about filters. The ideal filter is one that has cycled, or in other words, has all the bacteria it needs to make the pollutants in your water not harmful to your fish. 

So Nitrite is harmful too?

Yep the bacteria that sorts out the ammonia for you converts it into Nitrite. Its less harmful than ammonia but still toxic to fish. Use your test kit to find out what your level is. Once again a reading of 0 ppm is what you are aiming for, and anything over 0.1 ppm needs addressing.

How can I get rid of Nitrite if my reading is high?

Water change! Yep, you are getting the idea now, water changes are one of the most underrated cures for any problems with fish, stop being lazy and start doing a regular water change. A cycled tank/filter will remove nitrite for you, so its worth checking out how to cycle your tank and even getting it done before adding a single fish. Once you have the bacteria in your tank they convert the Nitrite to Nitrate.

Is Nitrate lethal too?

Nitrates are far less toxic than ammonia and nitrite though at levels of 100 ppm the fish will be impacted by its presence. Ideally you want a reading of 20 ppm and its worth checking out the Nitrate levels in your water straight from the tap, you cant reduce it lower if you "clean" water has a reading of 20ppm to start with! The only effective way to control Nitrate levels is to water change. Having a healthy planted tank can also go someway to using up Nitrate in the water as can various "nitrate removing filter sponges" available on the market, they must be changed in accordance with instructions to remain effective.

My brain hurts!

Yes I know, its a bit much, but basically, you need a cycled tank, a bacterial friendly environment and regular water changes. 

Brief: Your test kit should show a reading of 0 ppm for Ammonia and Nitrite and 20 ppm or less for Nitrate. With water that clean, your fish really have a much better chance of being healthy.

Ok... in my test kit I got the pH test too, what does that do?

pH is the measurement of acidity or alkalinity in the water. Thus the pH of battery acid is 1 and the pH of Milk of Magnesia is 10ish. As you can guess the pH of the water can really effect the fish. Each species of fish has a range it prefers, for example koi prefer pH7 to pH8.5 where as most tropical fish prefer the water slightly more acidic.  Its worth testing your water source to find out what the natural pH of the water is and then buy the appropriate fish rather than messing with the pH of the water manually. Fish get really stressed by rapid changes in pH and by fluctuating pH, so in general, leave the pH alone. The test kit is useful to check its maintaining a constant level.  Its not only the fish, even the nitrifying bacteria have a pH range they prefer!

Brief: pH is measured on a scale of 1 to 14. 7 is neutral. Lower than 7 is acidic, higher than 7 is alkaline.

I am experienced enough to mess with my pH, what should I use?

Adjusting pH should always be done gradually.

If you wish to lower your pH you can filter your water over peat, or add bogwood to the tank, though this has a minor effect. Often using CO2 for plant life has the additional effect of lowering your pH. An alternative is to use RO water ( Reverse Osmosis) or even an acid buffer out the bottle, ask at you Local Fish Store.

If you wish to raise your pH keep the water well aerated, remove added Co2, add crushed coral or seashells to the filter/tank. ( Crushed coral is often available at your Local Fish Store.) You could also try adding rock that contains limestone or alkaline buffer out the bottle, similar to the acid buffer mentioned above.

What if my pH seems to slightly vary during the day?

The pH value of ponds and tanks varies during the daytime and night time cycle. Plant growth changes the amount of CO2 in the water - as they grow they absorb the CO2.  Thus the pH may slightly rise during the day and drop back again during the night. A heavily planted tank will see this happen more noticeably than others.

My pH is very high, should I worry?

In general - No - however you should be aware that a higher pH can  lead to the harmless chemical ammonium ( NH4+) being converted to the harmful chemical ammonia ( NH3) far more readily, so checking your ammonia levels regularly is a good idea. The temperature of the water can also effect this process, but as it is quite complicated, I suggest further reading if you want to know more.

I keeping being asked what my KH is, what's that?

The same way as you can buy a kit from the LFS (Local Fish Store) for pH you can get them for KH and GH ( come to that next.) The KH of your water is its "temporary hardness". The carbonate and bicarbonate ions in the water effect its buffering capacity. This means that it will buffer/hold stable the properties of the water, importantly the pH. So if your pH fluctuates quickly you probably have a low KH, and if you have decided to make you hard tap water more acidic a high KH may make it extremely difficult. The more alkaline the water normally the higher the KH value.

Can I alter the KH then?

Yes, to raise it aerate the water ( thus driving off CO2), add baking  soda ( 5ml for every 50 litres of water) or try a product off the shelf to increase " buffering capacity". 

To lower it inject Co2, use RO water or one again buy a product off the shelf.

My KH is really low, do I have to do anything?

You should be aware that a particularly low KH reading can lead to inaccurate pH testkit readings. The levels of the components needed to determine the pH are not present in sufficient quantities to get you an accurate reading. Other readings however should not be effected.

Low KH can unfortunately result in some rapid changes in water parameters that can be harmful to fish a reading of 4dH and above is preferable and in most areas tap water is above that limit.


And how is it different from GH then?

GH is you water hardness, and that is created by magnesium and calcium ions. So when someone says a fish prefers hard water, it is the GH they are refering to. Generally though this will go hand in hand with the pH, an alkaline water being hard, and and acid water being soft. The measurement scale for GH is called OdH - degrees of hardness.  If you are given figures in ppm (parts per million) rather than OdH then  1 OdH is equal to approx 17.9 ppm.

0 to 4 OdH = very soft

18 to 30 OdH = hard

Different fish prefer different levels of hardness so its often a good idea to seek out fish that prefer the hardness you start with, or invest in RO technology. Live plants often enjoy a softer water ( 0 - 6 OdH) as do Discus, Angelfish and most tropical fishes. Goldfish and brackish fish prefer a harder water ( up to 22 OdH)

Can I alter my GH?

In much the same way as you KH you can, Add limestone to increase your KH which in turn will raise your GH or add Calcium Carbonate ( CaCO3). To lower it though you will really need to invest in the RO technology or an off the shelf product.

My GH is really high, is that a problem?

A very high GH can lead fish to be stressed and there may be problems getting them to breed. Stressed fish are more susceptible to other problems. You only really need to be concerned if your GH is above 17 OdH or 300 ppm.

Why do I have to use a water conditioner?

Although some people have their own well water or natural sources most fish keepers have to get their water from the tap. Water suppliers disinfect their water with Chlorine and/or Chloramine. Chlorine is a highly toxic gas and Chloramine is similar but a liquid. Both are toxic to fish. If you would like to know if either are in your water supply you can generally ask your local water authority to supply you with a list of everything contained in your water.

I thought you could just leave your water to stand overnight?

When only chlorine was added to the water this was mostly true as the gas will dissipate from the water over a period of time, however Chloramine is not removed in the same way. Another advantage of using a water conditioner is that they will often remove any other elements in the water that may be harmful to fish.

Should I use distilled water or just RO water then?

Fish need a number of trace elements in their water to be healthy, these include, magnesium, calcium, potassium, iron, zinc etc. Not only do these metals form with carbonate to create your GH but they play a roll in your water health. Both Distilled and RO water do not contain these elements and would need supplementing with minerals for best fish growth.

What is RO water?

RO stands for Reverse Osmosis. 

Essentially RO water is the purest drinking water possible. A cellophane type membrane separates treated water from non treated and due to the natural tendency of chemicals to reach the same pressure on either side of the membrane and pressure being applied to the untreated side the membrane filters the water.

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