Water for Discus
Written by Mary Ellen Sweeney
(Former editor of TFH magazine)

Discus are not really difficult to keep . . . as long as you do what they want! What discus want is: excellent water quality, free of toxins like chlorine, ammonia, nitrite, phosphate, etc.; correct water chemistry, pH and water hardness; and proper temperature, between 82 and 86F. Excellent water quality is provided by your three-part filtration system and one-part water changing system. Water chemistry is tested and determinations are made for adjustments. The water should be soft, between 3 and 15dH. The pH should be between 5 and 6.5. This is where most discus keepers have trouble. Discus would prefer not to compromise on these values. To believe that you can acclimate discus to harder water or to higher pH levels or lower temperatures is folly. The discus may live, may breed even, but they are living and breeding under stress. In fish, as in humans, stress shortens their lives and makes them more susceptible to disease. Strive for the ideal rather than trying to cheat the system.

WATER CHEMISTRY

You can probably walk into any pet shop and find out what the general water conditions are in your area. That would be fine if you were trying to decide whether to keep guppies or angelfish in your community aquarium, but it will not do for discus. You will need to test your water as it comes from the tap and continue to perform periodic tests to ensure that your aquarium water is up to par and within proper range for a number of values.

Testing the Waters
You should initially test for chloramine and chlorine, pH, and alkalinity. Once the levels of pH and alkalinity in your raw water have been established, you can decide how you want to handle the situation. Some raw water is just about perfect for discus with little or no modification. Some water needs extensive conditioning before the first fish can be introduced. Once you know these values, you may decide you want to keep another kind of fish! After the initial battery of water chemistry tests, you should continue to test the above, certainly after the first few water changes, and add a few more tests to the list: nitrite and nitrate, phosphate, and in the planted tank, iron and CO2. Simple, isn't it? Test kits have become very user-friendly in recent years. All these tests can be researched in a good chemistry book and the reagents assembled through chemistry supply outlets; however, the test kits and probes available for the aquarium hobby are generally inexpensive and easy to use.

Toxins in the Water Supply
The water company can be your friend or your foe. Chlorine or chloramine are routinely added to the water in many parts of the world. A simple color test kit will determine the presence and concentration of either. Removal of chlorine or chloramine is part of the process known as conditioning your water. There is more than one way to skin a cat, and there are many ways to condition your tapwater. Conditioning is the process of adjusting the chemistry of the water to bring it into line with the requirements of the fishes you are keeping. Chlorine is readily removed from tapwater by activated carbon prefiltration, aging the water, or permitting contact of the water with the air through the use of a spray. Chlorine can also be removed by adding prepared chlorine removers. If you are conditioning your water with reverse osmosis or deionization, these processes remove virtually all toxins (and a lot of necessary elements as well, that must be replaced), but more about reverse osmosis and deionization later. Chloramine is a combination of chlorine and ammonia, and some water companies need to use this for disinfection of the water supply. Chlorine is not good for fishes and chloramine is worse. If your test reveals chloramine, be sure to use a water conditioner that is chloramine specific. Aeration will not remove chloramine.

Water Hardness and Alkalinity
It may be that your water hardness and alkalinity are perfect for discus but unfortunately this is not always the case. It is far easier to adjust hardness and alkalinity upwards as when keeping hard-water fishes, but lowering these values is by no means impossible. It simply involves another step in the water conditioning process. Total hardness (general hardness) is the sum combination of carbonate and noncarbonate hardness of your water. Total hardness is measured as, degrees, dH, or ppm (parts per million). One dH is 17.9 ppm. How total hardness is expressed depends upon the author and his orientation. I prefer dH simply because as a discuskeeper, I like to see smaller numbers when I am measuring water hardness! If I were keeping African cichlids I might prefer to measure my water's hardness in ppm. Total hardness is usually not a big issue in keeping discus; alkalinity is a far more important factor in the breeding of discus. Alkalinity is sometimes referred to as carbonate hardness(KH)or buffering capacity. Alkalinity is the important factor in breeding discus and controlling the pH of the water. Alkalinity refers to the level of calcium, carbonate and bicarbonate in the water. It is measured in KH or mg/L CaCo3 or parts per million. One milligram per liter (mg/L) is the equivalent of one part per million. Soft water is 3dH and 0 to 50 mg/L CaCo3; medium soft water is 3 to 6 dH and 50 to 100 mg/L CaCo3; slightly hard water is 6 to 12 dH and 100 to 200 mg/L CaCo3; moderately hard water is 12 to 18 dH and 200 to 300 mg/L CaCo3; hard water is over 18 dH and over 300 mg/L CaCo3. The values for general hardness and alkalinity given above do not always match each other. It is entirely possible to have a higher reading of general hardness and a lower reading of alkalinity. The lower reading for alkalinity is the more desirable for discus water. Discus will do quite well in slightly to moderately hard water. In fact, many breeders routinely keep their fish in these values to ensure proper development of the young fish, but for development of the eggs, soft to moderately soft water, particularly concerning alkalinity is critical. Therefore, it is not necessary to drastically adjust the general hardness or alkalinity when you first start to keep discus unless the values are very high.

Reducing Water Hardness
It is best to test the pH and alkalinity of your water before making any investments in reverse osmosis or deionization equipment. As long as the general hardness and alkalinity are in the ranges mentioned above, you should have no trouble. Driftwood and peat will both contribute to softening of the water. You may find that your slightly to moderately hard water will respond very nicely to the introduction of a piece of drift wood and a bag of peat in your filter! Beyond this, or if you are at the stage where you are seriously considering breeding your discus, you can look into reverse osmosis or deionization pretreatment of your water. Both of these methods remove all trace of water hardness and a very high percentage of the impurities in the water, through extremely fine straining action in the R/O and specific resins in the DI. Water that has been handled in this fashion is stripped of necessary trace elements and must be reconstituted before use in the aquarium. Reconstituting salts are available commercially. Some authorities recommend mixing the water with 5% tap water, but if your tap water contains toxins, this is not the best method by any means. Household water softeners used in many homes are entirely unsuitable for preparing water for discus. The resins in these units exchange hardness ions for sodium ions and additional sodium is contraindicated in keeping discus.

About pH
Discus are very particular about pH. Keep your pH below 7 and above 5.5. The ideal pH for discus is 6. At pH levels above 7, discus are stressed. Below 5.5, the pH is inclined to plunge rapidly, so I find 6 to be comfortable for both the fish and the fish keeper. Alkalinity and pH are closely related. Hard water naturally tends to be alkaline. Soft water naturally tends to be acidic. This is because of the buffering capacity. Buffering capacity represents the presence of alkalinity (carbonate hardness) and the ability of the water to maintain high pH. It is a chemical balancing act. Just enough carbonate hardness and the pH remains at the desired level, too much carbonate hardness and the pH will remain high, too little carbonate hardness and the pH will crash. Maintain your carbonate hardness at around 10 or 15 dH and you should have no problems with pH. Check your pH with every water change until you are able to get a feel for how your water behaves. If you notice that the pH drops quickly, you must add back carbonate. If your pH resists change to lower values, you must remove carbonate. There are many methods of lowering your pH, most with some form of phosphoric acid, from drops to powders, but one of the gentlest and safest methods is through the use of peat moss. Because the peat adsorbs carbonates and acidifies the water, you should be able to maintain desirable pH and carbonate levels through the use of peat alone.

FILTRATION
Filtration is essential. Filtration is the life support system of the aquarium. Without filtration, your fish would soon die from the toxicity of their own waste.

The Nitrogen Cycle
In the aquarium, beneficial bacteria---known as nitrobacters--- colonize the biological filter media and every surface of the tank. Nitrosomonas sp. is the nitrobacter that consumes the toxic ammonia that is produced by decomposition of fish waste and other organic matter. The ammonia is reduced to nitrite. The nitrite is consumed by Nitrobacter sp. and reduced to nitrate, the least toxic end-product of nitrification. This process is called the nitrogen cycle and is the backbone of biological filtration. The nitrate is removed from the aquarium by your partial water changes (or in some cases by specific resins).

Mechanical Filtration
We start with the mechanical filtration. Sometimes this is called prefiltration. The main goal here is to remove large floating particles of uneaten food, fish waste, and plant waste. There are many ways to accomplish this: sponges, pads, floss; practically any inert mesh-type material that will capture the dirt. Simple filter floss is very inexpensive and effective. Depending upon the style of filter you choose, the prefilter media is situated where the water first enters the filter. It may be that you use a small sponge filter on the intake tube of your power or canister filter. Some filters have special chambers for prefiltration media. Even the old-fashioned box filter with a layer of gravel and some filter floss will perform effective mechanical filtration. These fine materials trap the dirt as the water passes through them. Mechanical filters must be changed or cleaned weekly. Most people do not realize that this is necessary! Mechanical filters capture the gross particulates, solid waste, which must be broken down to liquid before they can be converted by the nitrifying bacteria. It is far more practical to simply remove the solid waste than to wait for it to liquefy and then expect the biological filter to deal with toxins. This is an error that leads to an overtaxed filtration system. So whichever method of mechanical filtration you choose, keep it clean! This is one area where you don't have to worry about preserving your bacterial bed. Just wash, rinse, or replace that mechanical filter media as often as possible.

Biological Filtration
Mechanical filtration is meant to take particles out of the water, nothing more. Usually mechanical filtration is confused with biological filtration because the same media is sometimes incorrectly used for both types of filtration. Biological filtration is that bacterial conversion of nitrogenous compounds described above in the nitrogen cycle. Where you want to clean your mechanical filter vigorously and often, the biological filter performs best when it can be left strictly to its own devices with a constant flow of particle-free, oxygenated water through the media. There are many types of biological filters. The canister filter, which has been the mainstay of the advanced hobbyist, the trickle filter, which made its bones in the salt- water hobby, the simple box filter, which is used with tremendous success by experienced fishkeepers reluctant to give up on a filter that has been keeping fishes alive and well for the past fifty-odd years, the newcomer on the block, the fluidized bed biofilter, and many more. Some tanks are maintained for years with nothing more than a simple sponge filter and air pump. The sponge filter is gently squeezed in a bucket of tank water once a week and the resident nitrobacters do a fine job of converting the ammonia and nitrite. Regular siphoning of uneaten food and fish waste goes a long way to helping you keep a healthy tank with a very simple filtration set up.

As many different types of biological filter as there are, there are more types of media. Some examples of biological filter media include plastic hair curlers, "bio beads," gravel, sand, sintered glass, ceramic noodles, and so on. Biological filtration is critical to the health of your fish. Whichever media you employ to harbor your nitrifying bacteria, remember that you want to keep the bacteria safe from harm. It takes about six weeks for the nitrobacters to establish themselves in the filter. During this critical period, the ammonia and nitrite will reach high, maybe toxic levels. Keep your fish load very low in the new aquarium and be very careful not to overfeed. It is suggested that the tank be run with one or two very small and inexpensive fish during this period. The water may cloud up for a period, new tank syndrome. This is normal and will clear up presently. Once your filter bacteria have become established, the water will clear up spontaneously.

To maintain a healthy bacterial colony in the biological part of your filtration system, treat the media with gentle care. When cleaning the media, use only tank water. Do not use hot water or fresh tap water. A gentle rinse with tank water should be all you need to do if you have set up the system properly. The goal is to maintain the bacteria as undisturbed as possible on the media. If your tank is without power for any length of time, it is entirely possible that your biological filter will crash. This happens when the bacteria are without oxygen for a period of time. This time period varies depending upon a number of factors, but should you find that the filter has been off for a day, smells foul, and the fish are gasping for air at the surface, do not simply turn the filter back on! The filter has become toxic and must be thoroughly cleaned and the media replaced before it can be used on the aquarium.

Chemical Filtration
Some tanks do quite well without any type of chemical filtration at all. Frequent small water changes are employed to remove nitrate and other toxins. However, water chemistry varies radically in different areas and chemical filtration is sometimes necessary simply to keep the fish. If, for example, your tap water is very high in phosphate or nitrate, you may find that your fish don't do well until you pretreat the water with specific resins or activated carbon. While it is not within the scope of this article to go into great depth on water chemistry, be aware that there is virtually no water that cannot be made suitable to keep even such a delicate species as discus. Water chemistry is a fascinating study and in some areas it may be necessary to become quite adept at water chemistry and water treatment before you can keep discus successfully.

Activated Carbon
Activated carbon in granular or powdered form provides one type of chemical filtration. Activated carbon removes discoloration, dyes, colors, phosphate, chlorine, chloramine, antimony, arsenic, chromium, hydrogen peroxide, potassium permanganate, some of the heavy metals and many other toxins in varying degree. It also removes many fish medications at the end of therapy. It is ideal for prefiltration of the tapwater to remove most of the residual toxins left after municipal water treatment and some of the toxins that have been added in water treatment! Activated carbon does not remove ammonia, nitrite, or nitrate, so do not expect it to take the place of biological or mechanical filtration. It does what it does, and it does it well, and should be an integral part of your plan, but with full knowledge of its properties.  Activated carbon (AC) adsorbs the above named toxins. Based on the concentration of the toxin in the water, the effective lifespan of the carbon could be a few hours or a few days. Activated carbon is not meant to be used as filter media in biological filters. It is often combined with filter floss and left in the filter for an indeterminate period of time. This is not the correct way to use carbon. Once it has been used to remove toxins from the water, it should not be left in the aquarium to serve as a biological media. There are other, more appropriate media for this purpose.

Resins
Resins can be compared to magnets. The resin attracts a specific substance, like nitrate. The resin is usually placed in a canister and as the water passes through, it "grabs" all the nitrate. There are many different types of resins that capture many substances. Resins have a limited capacity and must be recharged in a brine solution when saturated. There are different grades of resins, some have a long life and some are exhausted quickly. There is no doubt that resins are highly effective and are used extensively in sophisticated filtration systems; however, if you use resin, you must adhere to a regular schedule of water testing and maintenance.

Really Really Fine Filters
Diatom and micron filters are used to capture super fine particles of dirt. The material, either diatomaceous earth or man-made micron filter material, is so dense that even many free-swimming parasites cannot pass through. The use of these materials for fine filtration is excellent for discus and their water.

Filter Flow Rate
For discus, you have to be a little careful. Some of the filters on the market utilize very high water flow rates. This is not good for discus. Remember that they need slow- moving water, hence, a filter that turns the water in the tank over many times an hour is not a good thing!

Peat in the Aquarium
Peat, from Canada and northern Germany, has been an aquarist's helper for generations. Peat is an amazing substance in that it gives off valuable tannic, fulvic, and humic acids that reduce pH and acts as a natural ion exchanger and reduces carbonate hardness in the water. Peat will also bind up some of the heavy metals and other toxins that may be present in the water. The active compounds in peat are also present in the natural black waters of the discus. It is all-natural and does wonders in the discus aquarium. True, peat filtration will color the water, but if the behavior of discus in peat-filtered water is any indication, discus really like amber-colored water! Peat filtration often triggers spawning in fish that have been flirting outrageously for months with no results! Peat is available in aquarium shops and garden centers. It even comes in neat little pellets that are easy to use and economical. There really is no excuse for not using peat in the aquarium. Just be careful if you buy your peat from the garden center. Be sure that is does not have any additives that could harm your fish. Peat is easy to use. Just pour about 1 quart of peat per 25 gallons of aquarium water into a bag or a lady's stocking and seal the bag. Slip this bag into your filter or place it in an area of the aquarium where water will flow through the bag. Replace the peat about every 30 days or when your pH tests start to show a rise in pH.