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Creating, Maintaining, Understanding and Enjoying a Coral Reef Aquarium

This article describes the steps taken to ensure a top-quality reef aquarium system, with advice given on all aspects of the system, and also a section on the methods used by both reputable, and unscrupulous suppliers to the trade.

Many expatriates, at one time or another, have looked at Marine Aquariums in our home country, but been put off Natural corals close upby either the high cost or the high level of maintenance required. Many expatriates purchase marine aquariums in Indonesia, as there is an abundance of outlets providing them. Many of the people I have spoken to or dealt with have bought their aquarium system at a bargain price as an “executive stress reliever”. Instead of stress relief, they only find that it creates more stress, when they see their fish and corals die rapidly and regularly, only to be told “The water is too cold”, or “It's normal for your fish to die” or “You need to buy this, that and the other” by an unqualified aquarium maintenance firm.

The truth of the matter is, good-quality filtration, lighting, and water movement are of paramount importance, and should be provided right from the start, as should quality fish and corals (inverts). Let's start at the very beginning!

Selecting a Tank

To reduce potential problems with water management, the first step is to select an aquarium as large as you feel you can accommodate. The greater the volume of working water, the more stable the conditions will remain, thus enabling you to duplicate a natural reef environment more closely. The tank dimensions should not be less than 100cm (40 in.) long x 70cm (28 in.) deep x 70cm (28 in.) wide. In volume terms, this is equivalent to approximately Selecting a tank600 liters or 156 U.S. gallons.

Glass or acrylic aquarium? Glass, although heavier, is less prone to scratching when cleaning. But, on the other hand, acrylic is more durable and is not restricted to being square or rectangular in shape. There are some really good acrylic designs available in Europe & the U.S.A., but supply in Indonesia is very limited and very expensive as it is imported from Germany or Japan.

Cabinet for your aquarium? Given the fact that many expats reside in Indonesia for 2-3 years, it is worthwhile to consider purchasing a good quality cabinet. Well-crafted cabinets are relatively inexpensive in Indonesia when compared to many other countries. The glass can be dismantled and flat-packed, and shipped home with the cabinet, pumps and lighting system in original containers. It can then be re-assembled back home. Some expats consider the purchase of a marine aquarium in Indonesia as an investment.

Water Temperature

Many books and articles advise that a healthy marine system containing fish, corals and plants requires temperatures of 23-25° C (73-77° F). For the Indo-Pacific species that are available in Indonesia, I have personally found, through much trial and error, that the temperature should be 24.-25.5° C (75-78° F) with the optimum temperature of 25° C (77° F). The lower end of this scale is predominantly for coral tanks and the upper end for aquariums with predominantly populated with fish.

Also, with respect to lighting, ensure that the hood is well ventilated so as not to warm the water too much. This isAquarium close up especially important because the level of dissolved oxygen in the water decreases with a rise in temperature thus leading to respiratory problems in fish and corals.

The most reliable way of keeping the temperature constant is to use a Chiller (Refrigeration unit ). These are effectively an Air Con unit specifically designed for this purpose. Chillers do not come too cheaply, but when you see the difference in how much the corals open up, and how healthy they become, the cost is quickly offset by not having to replace them regularly, and not having to run your home AC 24 hours a day.

If your water temperature is above 27° C , there is far less dissolved Oxygen in the water and the corals become bleached and rapidly die. Therefore, the Chiller cuts down the effect on the environment. I have corals that I have nurtured for many years due to the constant temperature and good water control.


Filtration is an essential element for marine reef aquariums, and really in-depth information could make up a book by itself. I will give a brief outline of the objectives of filtration, then make recommendations for the most effective and practical setup.

Understanding the Nitrogen Cycle

Simply put, the nitrogen cycle involves the breaking down of nitrogen-bearing organic compounds into simpler substances. This is done by specific bacteria. The metabolic processes of fish and the decay of uneaten foods first of all produce quantities of ammonia, which is quite harmful to fish and many other marine organisms. Fortunately, there are specific bacteria that break the ammonia down into nitrites, although these are still dangerous to fish.

But then the nitrites are broken down by yet another bacteria into nitrates, which are more easily tolerated than the two other substances. Algae and plants in marine aquariums utilize the nitrates in their metabolic processes; however, this is not done in a fast enough manner that the nitrate levels can be ignored, so they should be carefully monitored.

Methods of Filtration

The pros and cons of various filtration systems have been debated hard and long. Many marine inverts and animals are very sensitive to water conditions, and good filtration is the secret to successful reef-keeping. There are three main categories of filtration - Mechanical, Chemical, and Biological.

Mechanical filtration traps and removes suspended matter, i.e., waste products, and prevents chemical and biological filters from becoming clogged with debris. The most common form is spun nylon floss.

Chemical filtration is usually based on active carbon, which has the capacity to absorb the ions from dissolved waste onto its large surface area. It also harbors some of the bacteria responsible for breaking down potentially harmfulCorrect filtration is essential for a healthy tank ammonia and nitrites.

Biological filtration comes in a variety of forms. They cleanse the water by harnessing the biochemical properties of living bacteria and break down waste. They range from “undergravel” filters, which use the tank substrate as a filter, to more complex (yet surprisingly simple) systems. I have found advanced forms better, such as an above-water trickle filter, which allows a free flow of atmospheric oxygen to reach the bacteria. A much larger colonization of bacteria can be maintained by using a similarly sized filter bed below water.

I am a big believer in using Bioballs. These plastic balls, which look rather like stickle bricks, have a huge surface area, which means they are effective against even more bacteria.

Protein-Skimmers, sometimes referred to as water-fractionaters, work on the principle that it is easy to create bubbles in ocean water, and there is a collection of organic materials at the surface of those bubbles. If the bubbles are collected in a cup or have an overflow to dispose of them, organic materials can be removed even before they become part of the nitrogen cycle. The advantages are that the skimmer pulls the organics out before they have a chance to break down into harmful compounds. It also relieves the workload of your mechanical and chemical filters too.

Don't go away! I've said all I'm going to say about filtration.

PH Level

Ideally the PH level should be between 8.0 and 8.3, with an optimum level being at 8.2. The normal tendency is for the level to fall rather than rise, so PH levels should be monitored carefully by your aquarium maintenance service provider. See the section below on maintenance.

Water Movement

Many corals (marine invertebrates) are relatively immobile and need varying degrees of water movement to provide the high levels of oxygen they require. As food is normally carried to them in this way, water movement in the aquarium provides a vital function. There needs to be strong water movement at the surface to meet the oxygen requirements. In addition, a well-placed submersible pump is needed to create a current, which enables the corals to feed and open to their fullest extent. Although they are just like small rocks in their dormant state, some corals may occupy an area as much as 10 times bigger when fully open. It is very important that your supplier who decorates the tank understands which species should be positioned where, as there are those who require strong current and those who can't, along with those who thrive in quiet crevasses, and those who need strong light.


The final ingredient (except for water, rocks, inverts and fish) that we need to add is lighting. The goal is to replicate natural sunlight as closely as possible. Therefore, it is recommended to have a spectrum of blue (UV) light for 12 hours a day, and a full spectrum (white and UV) for 8-10 hours during a day. This would be the minimum.

The most commonly used lighting in Indonesia is in the form of imported, aquarium-specific neon tubes. These can be very effective if the mix and positioning is right, and they come at a fraction of the price of metal-halide units, which, although effective, cost more.

To ensure the well being of your inverts, it is essential that they receive adequate lighting. Adequate in this context means light of sufficient intensity and of the correct spectral wavelength.

Interior Décor

With the huge number of species and sub-species of corals, rocks and marine plants available in the Indo-Pacific region, one has to be very careful in choosing who does your aquarium décor. You want to enjoy your corals to their fullest extent, and also importantly, to preserve them and nurture them.

Consider the following points when deciding what items to put in your marine aquarium:

  • Do the corals like bright light, or sheltered nooks and crannies?
  • Do the corals need to be high in the water, or must they always be at the floor of the aquarium?
  • Do the corals need strong currents, or will that destroy them?
  • Do the corals thrive in very cold, cold, or even tepid water?
  • Do not leave these decisions to someone who is not highly knowledgeable in Marine Biology. Having asked these questions you will know if your supplier is knowledgeable enough.


A large number of species are available in Indonesia. However, many are not suitable for aquariums or have been Limit the number of fish in your tankcaptured using potassium cyanide, which is very common in Indonesia. Those captured with cyanide tend to die very quickly.

You need to be aware that it is not recommended to fill your aquarium full of fish, because:

  • Some fish who will eat your delicate corals.
  • Some fish will eat other fish or bully them to death.
  • Some fish give off toxins when dead (e.g. blowfish - puffers). These can wipe out an entire aquarium after they die.


Once you already have a system set up, there can be a great deal of work involved in sustaining it. Your maintenance package should include all of the following:

  • Weekly cleaning inside and out, including filters and lamps
  • Weekly testing using Electronic Test Apparatus for PH, Ammonia and Nitrite levels.
  • Weekly addition of Trace Elements from reputed manufacturers such as Kent Marine or Salifert of the US. You will need calcium, kalkwasser, strontium, molybednum, iodine, iron supplements as well as proteins for the inverts.
  • Fortnightly partial water change, if needed. Don't disturb the system if it's not required.

A professional aquarium maintenance firm will do their utmost to ensure that all conditions are at the optimum level in order to minimize the impact on the environment. Aquarium owners shouldn't have to change their corals every month. A reasonable replacement rate for a well set up and maintained system is about 5% replacement per month maximum.

Suppliers to the Coral and Marine Fish trade

There are two types of suppliers to the trade. Those who are licensed by CITES (Convention for International Maintaining your aquarium should be done by a professionalTrade in Endangered Species), and those who are not. Those who are licensed have an annual quota, which cannot be exceeded. As they are generally exporters, the marine trade is a big business for them. They have a responsibility to only harvest from sustainable, designated areas. In addition, they also have to contribute to marine conservation, according to the size of their quota.

On the other hand, there are those who simply view marine life forms as produce. The professional aquarium maintainers should choose to purchase only from reputable, selected exporters, enabling them to obtain only the best, export quality corals and fish. If the corals are in peak condition, they can be nurtured and grown for many years. Ask a potential maintainer what their suppliers do to minimize their impact on the marine environment.

Marine aquariums, properly set up, stocked and maintained can indeed provide much needed stress relief. The beauty of a well-stocked diverse marine aquarium can be astounding and provide many enjoyable hours of viewing pleasure. Ensure that you choose a professional aquarium maintenance firm so that your pleasure doesn't turn into an expensive nightmare.

This article has been provided by John Duffy, an expat living in Jakarta. Contact him if you have any questions about marine aquariums at 0818-488961 or email PMAQ@Hotmail.com.