Starting a Saltwater Aquarium

OK! You’ve heard about Coral Fish and now you see for yourself all of these incredibly beautiful fish- from the ferocious looking Dragon Eel to our truly unique state fish, the Humuhumunukunukuapua’a. You may also be wondering, “Is it difficult to maintain a saltwater aquarium?” The answer is as simple as the question…NO! It is not difficult! All you need is a little patience and a few simple guidelines to follow. Keeping this in mind, you will enjoy a truly unique environment within your home or business. Listed below are 12 basic guidelines that should be followed for a successful saltwater aquarium. Enjoy your marine aquarium and remember: You pay for what you get…so get good, reliable equipment. If you have further questions, please feel free to consult our expert sales staff at Coral Fish Hawaii. Mahalo!!

Tank Size

As a general rule, a saltwater aquarium should not be smaller than 20 gallons if you plan on keeping fish. However, most invertebrates, such as crabs and shrimp, can be kept in smaller tanks.


All saltwater aquariums should be equipped with both a “biological” and a “mechanical” filter. A Biological Filter utilizes bacteria to break down the ammonia. The biological filters we sell are primarily the Undergravel Filter and the Wet- Dry Filter. The “undergravel filter” utilizes gravel to maintain a healthy bacterial population. This filter, although more economical, tends to be a little more labor intensive as you will need to vacuum the waste from the gravel occasionally.

The “wet-dry filter” utilizes plastic bio-balls to maintain bacterial populations. Although this filter is more expensive than the UGF, it maintains healthier biological population, which is better for the aquarium.

A Mechanical Filter, also critical in maintaining a healthy fish population, is necessary for ridding the aquarium of unwanted pollutants and debris. Most people use cartridge or canister filters for achieving this filtration. These particular filters typically use carbon and filter pads to “cleanse” your aquarium of free floating debris.


These little organisms are critical in establishing and maintaining a successful saltwater aquarium, and are developed and maintained through the use of either an undergravel or wet-dry filter. Once the established in your aquarium, the bacteria will consume and break down the waste products of the fish. Without bacteria, the ammonia levels will rise resulting in a toxic environment for your aquarium. It must be noted that newly established aquariums have no bacteria and it typically takes 6-8 weeks to establish a healthy population.

Technically, there are (2) types of bacteria that need to be established in a saltwater aquarium: Nitrosomas and Nitrobacter. The Nitrosomas bacteria, establishes itself first and essentially “eats” up the raw ammonia that was expelled from the fish. After it consumes the ammonia it releases a form of ammonia called Nitrites. Only after the Nitrites are established does the Nitrobacter bacteria appear. Once established, the Nitrobacter “eats” up the Nitrites that was dispelled by the Nitrosomas bacteria and releases a less non toxic form of ammonia-Nitrates. Note: This natural miracle of breaking down ammonia waste into Nitrites and Nitrates using two types of bacteria is essentially the same principle all sewage treatment plants use when breaking down our waste and rereleasing it back into the environment.

Therefore, because of the initial toxic ammonia levels, most people start off with “starter fish” until the aquarium has been established with healthy bacterial populations.

It must be noted that bacteria need surface area to grow and develop.

Consequently, the more surface area the filter area provides, the healthier the aquarium will be.


Although ammonia has various levels of toxicity-such as Nitrites and Nitrates, Nitrites are usually the main cause of death in newly established aquariums. Since high nitrite readings are normal in the break-in period, it is advised to put only hardy fish in the aquarium at first- and only in small numbers. Fish that can tolerate the high toxic levels are damsels, clowns, eels, and invertebrates.

Powerheads and Air Pumps

Powerheads are used primarily for powering up the undergravel filter. By positioning it on top of the uplift tubes of the undergravel filter, the powerhead draws water up into the aquarium where it re-circulates down thru the gravel (where the bacteria lives) into the bottom of the undergravel filter. Powerheads can also be used to create currents in your aquarium. Now, although air pumps can also be used to power undergravel filters, they are mostly used for aeration and powering decorations.


Gravel for the saltwater aquarium should be of the calcium carbonate variety and not the colored variety found in the freshwater section. This type of gravel will help maintain proper pH, and provide a suitable environment for your bacteria to grow. If you’re using an undergravel filter, use approximately 1 lb/gal (i.e. 55 gallon aquarium= 55lbs.). If you have a wet-dry filter, the gravel is not a necessity for biological filtration so approx half that amount should suffice.


One of the key ingredients for a successful aquarium is water purity. We always like to recommend Instant Ocean. This product duplicates the essential minerals and trace elements found in seawater and prevents the introduction of pollutants and hazardous micro-organisms sometimes found in natural seawater. Because synthetic salt comes in a dry form, much like our Hawaiian salt, you must add fresh water, using a hydrometer to determine saltiness (salinity). If you prefer, natural seawater can be acquired from the Waikiki Aquarium (membership & appointment necessary) or Anuinui Fisheries on Sand Island Rd (just past the Coast Guard station)


This salinity measuring device is a necessity for any marine aquarium. Most fish are best kept at salinity (specific gravity) of between 1.015-1.018, whereas most invertebrates are best kept at normal ocean salinity of 1.024. Note: There will be occasional evaporation in your aquarium, so check periodically, and add fresh water if needed. Remember that salt in saltwater does not evaporate!!

Water Changes

Another important guideline applicable to both fresh and saltwater aquaria is maintaining regular monthly water changes of 20%. This prevents to accumulation of fouling wastes such as nitrates.

IMPORTANT: When a water change is made, make sure the new water is exactly the same temperature and salinity as the water being replaced. If not, undue stress may occur, weakening your fish and making them susceptible to getting parasites or Ick (click here to learn about “Ick-white spot disease”) It is also recommended that a water conditioner such as “Novaqua” or “Stress Coat” be used in conjunction with water changes.

Coral-Natural and Artificial

All aquarium fish need someplace to hide providing security and cover from a sometimes overly aggressive tank mate. By providing ample coral and base rock to your aquarium, the fish tend to be much happier and are less stressed-not to mention having a great aquarium to look at and enjoy!!!

Coral Fish offers both natural coral, which has been harvested ecologically, and a large variety of artificial corals, which, by the way, are often difficult to differentiate from the real thing!!

Note: Once coral (or any decoration) is placed into an aquarium, brown algae eventually starts to form. This algae grows faster when the aquarium is exposed to sunlight-so before setting up your aquarium, think about where the best place may be limiting direct sunlight.

Cleaning this brown algae from your decorations can be done simply in one of two ways: BLEACHING or BOILING. Bleaching involves placing the algae covered coral into a 5 gal bucket with 2 cups of liquid bleach for _ hour and rinsing thoroughly. If the coral still has a “chlorine smell”, leave out in the sun to dry for a day. It is important that the coral has no smell to it before placing back into the aquarium. The other option is by boiling the coral for 5 min.


Always make sure you have a cover (and light) on your aquarium, as fish can jump out and this can get costly….not to mention losing a “pet”. By covering the aquarium, water will be less likely to evaporate as quickly.

How Many???

This is probably the most asked question we are asked at Coral Fish. Unfortunately, we do not have a definitive answer. A lot depends on the size and type of fish you decide to keep. However, a good rule of thumb is to add one or two fish at a time-allowing the bacteria to grow in proportion to the added biomass /fish. Then, use the Nitrite test kit to tell when it it safe to add more.

Important: Remember that saltwater fish are not domesticated like most freshwater fish and require extra space in which to swim. So with this in mind, keep the marine aquarium sparsely populated and your fish will live a healthy and long life !

A Final Guideline: Have Fun !!!!

Ich or “White Spot Disease”

OK!.... Now that your aquarium is running smoothly, you should be constantly on the lookout for what is commonly known as “Ick”. This parasitic infection is the number one killer of saltwater fish. With routine spot checks on your fish and regular treatments of copper sulfate in your aquarium, the hobbyist should not have to worry about this deadly disease.


Ich, which is also called “white-spot disease”, is a parasite which has the ability to complete its 14 day life cycle in your ‘closed’ aquarium system. The life cycle is typically divided into 3 stages:

  • Stage 1
      This stage the “Ich” lays dormant in the gravel as a cyst-like ball. Copper treatment is not effective during this period

  • Stage 2
      This second stage occurs when the cyst-like ball breaks open and a free swimming flagellate appears and starts swimming looking for a host (fish). If the flagellate cannot find a host I attach itself to within 48 hrs, it will die.

  • Stage 3
      This third stage occurs only if the parasite finds a fish. It is hear where the parasite becomes visible on the fish. This stage is lethal, unless treated immediately with copper sulfate.

What to look for

Now that you know a little about the life cycle of this organism, what do you look for? In both the first and second stages, it is nearly impossible to identify. Only in the 3rd stage does the parasite become parasitic on the host fish becoming readily apparent.

Typically, ”Ick” first forms as a cloudiness on the clear portions of the pectoral (side) fins and/or caudal (back) fin. Other symptoms include cloudiness of eyes or unusual scratching.


If left untreated, the parasite will work its way onto the body of the fish eventually working its way to the gills. Once encrusted on the gills, the parasite will prevent Oxygen exchange and will eventually suffocate the fish- This is what causes the heavier than normal respiration.


If you fish develops “Ick” and if caught in time, treatment with copper sulfate combined with proper monitoring of concentration levels with a copper test kit should kill off the parasite. It must be noted that when medicating, a concentration of .15-.23 ppm should be maintained for a pfish eriod of 12-14 days. This should be adequate to kill off some of the deadliest stages of the parasite.


It must be emphasized that “Ick” is always present in your tank as a cyst…and it can and will flare up, usually at the onset of STRESS in the aquarium. Simply put: Anytime a fish becomes stressed ( either because of massive water changes, undo temperature changes or overly aggressive fish), it can lose its natural protective slime coating. This allows the “Ich” parasite to access the fish’s skin, setting the stage for a repeating cycle of infection.

At Coral Fish, we keep trace amounts of Copper (.05-.06) in our Fish system at all times. You may do the same by medicating your aquarium periodically. If this is done, you must remember that invertebrates cannot be kept in the same tank due to their high sensitivity to copper.

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