10 Golden Rules
The 10 Golden Rules for maintaining an optimum aquarium provide the rules for a well functioning aquarium in which fish and plants are able to lead a healthy, vigorous life. They remove the factor of uncertaintv from the aquarium from the very beginning and render it independent of chance occurences. With its aquaristics systems Dupla provides high-quality appliances and products by means of which the "Optimum Aquarium" is realizable and reproduceable. The following pages provide the modules step by step which you require in order to reach this target.

1. Tropical warmth in the substrate
The heating system developed by Dupla Duplamat and Duplaflex (a low-voltage bed heating svstem). influences life in the aquarium very decisively: the heating cable (on the bed of the aquarium) integrates the entire bed soil into the chemical and physical cycle of the aquarium by means of the upward current of water caused by it. This ideal aquarium heating system fulfils several requirements simultaneously:
1. The same temperature in the water and in the bed, just as in natural waters. (If the aquarium water is heated up e.g. by means of heating bars, only the water becomes tropically warmy whilst the bed soil remains at room temperature and the plants notoriously suffer from "cold feet").
2. Bed water currents which prevail in natural waters are copied; nutrients are fed to the roots, the materials discharged by the roots are carried away.
3. A stable redox potential in the bed. The bed is prevented from turning black and an optimum stock of iron is supplied to the plants, as in tropical waters in conjunction with Duplarit (see section "plant nutrition in accordance with nature").
4. Absolute safety for man and fish, even if the heating cable is damaged.

2. Adapted light
The Dupla lighting system exclusively comprises lighting fittings (Duplalux, Duplalux LI, Duplalux Coral and Milux 60) which reproduce the natural light in fishes and plants' natural biotope both in fresh water and in sea water in an excellent manner. They thus fulfil the two important functions of light:
a) to put the underwater world in the right light setting and
b) to supply the necessary energy for plant growth.

Criteria for aquarium lighting
1. Light's most important function is to provide the aquarium plants with sufficient energy for optimum metabolism; amongst other things the assimilation of nutrients incl. CO₂ and the discharge of oxygen to the water. In the aquarium this is also easy to check by measurement of the oxygen (Dupla O₂ test): - Towards evening 100 % oxygen saturation should be achieved.
2. The light day under water is shorter in tropical waters than the light day above water. This is a consequence of the angle of refraction in the water. The sunrays do not penetrate the water until they are at a certain height above the horizon. Thus the light day under water amounts to approx. 8 to 10 hours. The consequence for the aquarium: strong light but a shorter period of illumination. Even 14 hours do not bring about 100 % oxygen saturation.
3. Many plants which are used in the aquarium as foreground plants, e.g. echinodorus tenellus, lilaeopsis nova-zelandiae etc., grow on embankments and receive the most light there. If the lighting is weak though, they will obtain too little light in the aquarium, assimilate only inadequately and rot.
4. The Dupla lighting system offers with its adequate lightings the ideal light for the different requirements in the aquarium.

3. Assured water stability
Tropical waters, especially flowing waters have a surprising degree of stability independent of the season, water level and light conditions. Factors such as the pH-value, the CO₂ content, degree of hardness etc. have only a slight fluctuation range. Several functions are also dealt with simultaneously by the Dupla CO₂ system, which assures stability in the aquarium:
1. Constant pH-value
In the optimum community aquarium in which tropical fish from geographically and chemically different waters can be cared for, a neutral pH-value setting is recommended. Both fish from weakly acidic waters (e.g. neon fish) and also those from slightly alkaline waters (e.g. Lake Malawi or Lake Tanganyika) find an optimum tolerance range here. The CO₂ system also offers great advantages for specialized aquariums in which special fish species, e.g. discus fish, can be cared for or bred. Due to the precisely determined CO₂ dosage (Dupla pH-Control) both acid and alkaline pH ranges are able to be programmed and set so as to be stable.
2. Stable carbonate hardness
If an aquarium suffers from CO₂ deficiency, the following sequence will occur: - Carbon is chemically bound in the carbonates. Now the plants need this carbon, since a different source is not available. In this process, so-called biogene decalcification, carbonates are destroyed. As a consequence the carbonate hardness drops to dangerously low values and the pH-value becomes extremely unstable, however, with sufficient CO₂ supply the plants utilize the carbon contained in the carbon dioxide. Biogene decalcification no longer occurs and the stability of the water is assured.
3. Optimum carbon supply
Submerged water plants meet their carbon requirements preferablv from gaseous, solute carbon dioxide in the water. The supply from carbonates, which is also possible leads as described above, to greater problems. Optimum carbon supply is assured by Dupla CO₂ fertilization.

The CO₂ Table
This table will assist in determining the exact requirements of any given aquarium, particularly in respect of CO₂ fertilization. It confirms the rule that optimum pH regulation by means of CO₂ diffusion leads to the optimum availability of carbon for the plants. It also highlights the exceptions to this rule, however, in that water containing a carbonate hardness of less than 3 to 4 degrees can suffer a shortage of CO₂ very quickly. In fact at neutral pH-levels the CO₂ content is already very low! In the case of a carbonate hardness less than 3 to 4 degrees the pH-value should be decreased to 6.4. Under these conditions even the Dupla CO₂ test can show misleading results if the carbonate hardness is less than 3.5 degrees due to the presence of humic acids, high nitrate values, and other substances that "fool" the test into thinkine that CO₂ is present.

4. Plant Nutrition Corresponding with Nature
Contrary to tropical plant waters, our tap-water has large nutrient deficiencies. Many important plant nutrients and trace elements are missing or extracted from the water during treatment at the waterworks. However, if a nutrient is missing, even if only temporarily, the plants' growth will be stunted or the plants perish (Liebigs's law of minimums). In order to ensure healthy plant growth in the aquarium, the nutrient deficiencies in the tap-water have to be stocked up and supplemented, so that good "aquarium water" is derived from tap-water. For this purpose it is decisive that the nutrients are in a very certain ratio to one another. Several "critical nutrients", in particular iron and a series of trace elements, present special problems in solving this task; they are required in only minute quantities. In larger doses their effect is poisonous. In aquariums they may not be administered for days and weeks in advance, e.g. if the water is changed. The situation is rendered more serious if various trace elements are not only being consumed by the plants but also being precipitated by chemical reactions. This has always presented plant fertilization in the aquarium with special problems.

Duplarit G and Duplarit K - A substrate additive and root nutrient
Duplarit consists of selected tropical laterite with a high iron content. Duplarit conditions the bed soil in the aquarium just as it is encountered in tropical plant waters.
Duplarit G, a granulate, is added to the bed material when the aquarium is initially set up. A root activation tablet is enclosed in the Duplarit G pack for the purpose of rapid root formation. Duplarit K, which is ball-shaped, is used for retreatment of the bed soil in the aquarium.

Duplaplant - the basic fertilizer
Duplaplant contains all important plant nutrients which are missing from tap-water; in addition all trace elements which remain available in the aquarium for a short time. Important: Duplaplant is dosed in accordance with the total volume when the aquarium is initially set up; when the water is changed only in accordance with the proportion of fresh water.

Duplaplant 24 - it the daily fertilizer
It is extremely important for the growth of aquarium plants that fertilization is not performed so as to provide reserve stocks, but only in low daily quantities. All oxydizable trace elements and iron are bound by means of chelation and are thus soluble over a long period of time. Important: The need for nutrients in the aquarium is dependent on the plant quantity, lighting and other factors. A repeated check on requirements is therefore recommended by measurement of the iron (Duplatest Fe).

5. Biological Filtration
Aquariums are fundamentally over-populated with fish relative to their water volume. Metabolic products from fish, but also from snails, plants and other sources build up and contaminate the water. The aquarium owner counters this process by changing the water regularly and by means of suitable filtration. Purely mechanical filtration by means of cotton wool, carbon, clay tubes etc. is being replaced more and more by "biological" filtration. "Biological" means: filtration by means of a medium colonized by bacteria which remove all materials contaminating the water and thus assure cleaning of the aquarium water. Specific bacteria are also able to even regulate the remains of chelate compounds and over-fertilized chelated. Industrial discharge water techniques also make extensive use of this filtering technique. Regeneration of the contaminated water is possible up to the point of drinking-water quality.

The Dupla Biokaskade
The Dupla Biokaskade has been especially developed for the trickle filter system. This concerns an ingenious plastic framework with a particularly large surface. It is so designed that extensive bacterial colonies are able to form on without the filter surface closing up and becoming smaller, as does happen with fine textured filter elements. The Dupla Biokaskade is deployed principally in trickle filters. Filter volume: 2-5 % of the aquarium water. If a suitable pre-filter is utilized. which is cleaned regularly, the Biokaskade filter is able to function continuously as an "eternal filter" without maintenance. Bacteria colonies which have grown excessively, break off and are flushed away. The filter is self-cleaning.

The Dupla Minikaskade
Filter media for biological filtration. The Dupla Minikaskade has been especially developed for the use in closed filter systems, e.g. circulation filter. It has an extremely large surface of 3900 mm², and due to its small dimension and the optimum space utilization, the Minikaskade provides full efficiency in small filter systems as well.

6. Strong Water Movements
Good to strong water movements are the following reasons:
I. Water movement having an effect from the surface of the water down to the bed soil will assure even temperatures in all zones of the aquarium.
2. Only a strong movement of water will manage to carry away organic waste materials lying on the surface of large-sized plant leaves. e. g. Echinodorus, Cryptocorynen, Anubias etc. If there is excessively weak water movement, adhesion forces firmly hold a stable film of water on the leaves' surface, thus hindering interchange processes or even eliminating them altogether.
3. Water zones with fresh nutrients reach the leaves surfaces by means of water movement.
4. Provide a strong current for the fish. Many fish need this, especially those coming from rapid flowing streams.

7. Dense Planting
The optimum aquarium is dependent on dense and well growing plants. The advantages of a well planted aquarium are:
- Decorative overall impression.
- The substrate is kept in shape by the roots.
- Oxygen is released by the roots to all areas of the substrate.
- This prevents the substrate from turning black.
- Well growing plants provide optimum oxygenation.
- Well growing plants are an excellent protection against algae of all kinds.
- Well growing plants inhibit disease causing organisms.
- Well growing plants remove toxic elements from the water.
- Several aquarium plants release antibiotic-like substances in the water.
- Dense planting provides good hiding and spawning places.

The solution for an optimum aquarium:
I. Use pre-cultivated plants adjusted to aquarium conditions.
2. The aquarium must be densely planted from the very beginning. Use many different types of plants that crow slowlv, stay small and crow offshoots. Tall growing plants that float on the surface must be regularly trimmed back to prevent them from cutting out the light to the plants underneath. Plants should not really get taller than the aquarium.
3. All growth factors must be met. See headines 1, 2, 3 and 4.

10 points for correct algae prophylaxis
1. Plant densely with fast-growing plants upon initial. The greatest algae danger exists during an aquarium's initial phase. Fast growing plants overcome this phase best of all due to the aquarium's better oxygen supply. Later they can be partially replaced by slower crowing plants, e.g. Cryptocorynen, Anubias etc.
2. Right from the start deployment of algae-eating fish:
Epalzeorhynchus siamensi (against barb algae, brush algae and green algae), Otocinclus vittatus, O.affinis, Poecilia shenops, Plecostomus punctatus, Barbus conconius, Farlowella acus etc.
3. Continuity of all conditions:
Good lighting, neutral and constant pH-value (6.8-7.2), permanent availability of all plant nutrients, continous CO₂ supply.
4. Correct bed soil: Quartz gravel. 2-3 mm grin, the bottom third being mixed with Duplarit.
5. No nitrates, no phosphate content = excellent algae climate. Prevention: water change, dense vegetation, possibly desalinate.
6. Use only precultivated plants. Be careful with directly imported plants. The spores of tropical algae can be introduced by this means
7 Be careful when adding or replacing fish or plants from other aquariums! Algae spores can very easily be undesirably transferred by this means, and will possibly "explode" in the new aquarium due to better habitat conditions.
8. Do not use any decorative materials containing calcium: Stones, gravel etc. Calcium sample: Test gravel using hydrochloric acid. If it contains calcium, the gravel will foam.
9. No prevention by means of algicides (algae control agents). This harms the plants more than the algae.
10. Don't put transportation water into the aquarium. When adding new fish and plants the transportation water should not be put into the aquarium. Insert fish using a net.

8. Balanced Fish Population
A balanced fish population goes hand in hand with the idea of providing both fish and plants with an environment that is optimally designed. In the optimum aquarium fish and plants should be a harmonious combination.

Here are some basic rules:
- Do not mix fish that are incompatible.
- Do not add fish that eat plants.
- Make sure you introduce algae eating fish right from the start, see also "Algae prophylaxis".
- Make sure the fish you put in all have the same temperature requirements, usually 25 to 26^oC (76-78^oF).
- To prevent an excessive snail population, a snail eater may be added.
- Choose fish that occupy all levels of the aquarium: Bottom, top and mid level.
- Do not add picky eaters if you are not sure that you will be able to provide them with the food they need.

9. Fish Care Compatible with the Tropics
DuplaRin is a modern feed concept for aquarium fish. It was developed in many vears of research and trial work together with the leadino scientists. Prof. Dr. RoIf Geisler and Dr. Rudolf Lörz. DuplaRin is a granulate in various sizes; a suitable type for any fish and mouth size. In addition DuplaRin is supplied with specific recipes as extremely fine feed, DuplaRin Micro, and as tablets (Compretten and llaftys).

Feeding the fish by means of DuplaRin
DuplaRin's main advantages:
I. DuplaRin is free from colorants. For this reason it is particularly easy to digest and is wholesome. It consists of valuable raw materials which promote the health of aquarium fish by means of their balanced composition.
2. DuplaRin is fish-mouth sized and adapted to fish's eating habits. Fish are piecemeal eaters, and because their mouths differ. DuplaRin is supplied in various sizes of granulate between 0.25 and 1.6 mm.
3. DuplaRin is a 3 stage feed, for, it is capable of floating, being kept in suspension and sinking. By this means surface feeders, fish in the middle zone and also bed feeding fish equally all obtain fresh and full-value nutrition.
4 DuplaRin is stable in water. It soaks up water slowly without losing its shape or disintegrating in doing so. The valuable content materials are retained and are not leached. Thus the aquarium fish constantly get high-quality feed.
5. DuplaRin is produced in the expansion process. The carefully selected tropical microalgae, vitamins, proteins, trace elements etc. are fully retained by means of this particularly gentle process.
6. DuplaRin is packed in tins which are sealtight against vapour. In this way DuplaRin remains fresh and maintains a shelf-life, without loss of quality. This is one of the prerequisites for the freshness guarantee provided by Dupla.
7 DuplaRin is ideal for dosing. A new way of feeding aquarium fish has been introduced with the dosing device which was specially developed for DuplaRin granulate. The dosing device allows objective, precise and hygienic feeding without losses.

10. Control of All Variables
The Dupla Analytical System
Preventing aquarium conditions from getting out of control unnoticed, through the regular testing of, for example, temperature, pH, nitrite content, iron content, carbonate hardness, and other factors. Compared to natural waters, an aquarium is a verv small mass of water. Test values can go from one extreme to another over very short periods of time. We, however, require a high degree of stability and continuitv, For this reason Dupla has developed an analytical system that serves both a diagnostic and therapeutic function.