FOWLR Aquarium
by Sam Pol
(Updated 10-28-07)

A large saltwater FOWLR style aquarium with aggressive species.

Table of Contents FOWLR Aquarium Equipment Habitat Water Chemistry Setup Species Feeding Maintenance Other Info

A FOWLR style aquarium refers to a saltwater setup consisting of Fish Only With Live Rock. Traditional Marine aquariums in the past were setup with artificial plastic decorations and “fake”, dried coral. This old school method for setting up a marine fish aquarium does not make for a natural display and reduces the survivability of the fish. Using live rock for your aquascaping in a marine aquarium provides a much more natural look and allows for a natural filtration technique. The techniques that we recommend are not that different than the methods used for maintaining a reef aquarium. You would be able to convert this style aquarium to a reef style later on depending on your fish selections.

Saltwater Aquariums…Easier Than Ever!
A FOWLR style aquarium offers the hobbyist the opportunity to set up a saltwater system that is both easy to maintain and tremendously enjoyable. It also offers the opportunity to keep certain fish that are not considered reef-safe or the "aggressive and semi-aggressive species" such as Lionfish, Triggers, Tuskfish, and other larger, predatory fish.

The more common setup is the peaceful "community aquarium" with the smaller, more omnivorous fish like Clownfish, Chromis, Cardinals and Dwarf Angels. Choosing these types of fish will make it easier to convert your aquarium to a reef aquarium later on. Some of these species may still be territorial and should be carefully matched for compatibility. We will offer some more suggestions on certain species later in this article.

Aquarium
We recommend a size of at least 50 gallons for a FOWLR style aquarium. Larger aquariums of a minimum of 75 gallons are required for other species such as Triggers and Lionfish. Be sure you decide on the fish you would like to keep and research their space requirements before you purchase an aquarium.

SeaClear 50 Gallon Regular

Protein Skimmer
Protein Skimmers are also desirable in a FOWLR style aquarium. Protein Skimmers remove organic material from the water before it starts to break down into ammonia. This reduces the work on the rest of the filtration system and makes maintaining water quality much easier. The one disadvantage with running a skimmer is that they may remove some trace elements from the water. The trace element levels can be maintained with regular water changes and the occasional use of trace additives. Be sure to choose the correct size protein skimmer for your aquarium.

Remora Protein Skimmer

Saltwater Additives

Live Rock is the primary filtration and decoration in the saltwater aquarium.

Live Rock
The primary filtration in a FOWLR style aquarium should be the live rock. Live rock refers to pieces of coral or coral rock from the coral reef that have broken off and fallen to the ocean bottom and become covered with encrusting organisms, such as coralline algae and sponges. Live rock will be the main biological filter of your saltwater aquarium, while at the same time enhancing the look of the aquarium and providing a natural shelter for the inhabitants.

Live Sand
Live sand also plays an important role in filtration. Live sand refers to a sand bed that has become colonized with nitrifying bacteria. This can happen naturally over time or the sand bed can be seeded with pre-colonized sand from an established saltwater aquarium or you may also purchase pre-colonized live sand.

Wet-Dry Sump
These are similar to canister filters in that they are positioned under the tank and operate on a siphon and return powered by a pump. These style filters require an overflow or plumbing-ready tank for proper operation. They enhance biological filtration as well as mechanical filtration with the proper pump they will cut down maintenance time and do a much better job than traditional filters including canister filters. The sump area (wet area) of these filters can also contain additional equipment including heaters and thermometers. This allows you to keep these parts out of the aquarium providing a cleaner looking setup. The bio media area (dry area) of these filters is eposed to air allowing for excellent gas exchange providing valuable oxygen to the aqurium and removing excess harmful nitrogen.

Pro Clear 60 Wet-Dry Filter

Lighting
Lighting in a FOWLR aquarium is not as critical as it is in a reef aquarium. You will need about 2-3 watts per gallon of light for 10 hours a day. We also recommend a mixed daylight spectrum combining 6700K and 10,000K bulbs to render the best colors of your fish. Actinic lights can also enhance the look of saltwater fish and provide the deepwater spectrum of light necessary for photosynthetic animals such as Anemones and Corals.

36" Satellite 1x96 Watt w/Lunar Light

Retrofit Lighting as an Option
You can also use a retrofit light kit to add lighting to an aquarium canopy. The use of a full canopy enhances the aquarium looks making it more like a home furnishing than a "fish tank". Adding a compact fluorescent retrofit kit provides balanced, efficient lighting for the marine aquarium.

36" Sunpaq 1x96 Watt Retrofit Kit

Water Movement
Water movement is important in a FOWLR aquarium to prevent dead spots and provide suitable water movement through the natural live rock filter. You will also need a pump to supply water flow through your refugium system. You will need a turnover flow rate of at least 5-7 times the aquarium volume per hour. A 50 gallon aquarium would require a minimum of 250 to 350 gallons per hour of turnover. Having an extra powerhead in the aquarium will provide some of the additional flow creating "currents".

Maxi-Jet 900

Heating
Having super reliable heating in any style aquarium is very important. Most saltwater fish prefer a water temperature of 76-78F. A good rule of thumb for selecting aquarium heaters is to have about 3-5 watts per gallon.

Hydor Theo 200 Watt Heater

Other Equipment
We recommend the use of a digital thermometer. The accuracy of these units is amazing and most have a built in alarm for low/high temperature. This offers better protection for your investment in your aquatic pets than the cheaper thermometers.

Digital Thermometer

Habitat

Recreating the Reef
Lets take a look at the decoration of a FOWLR style aquarium. This style is not far from what would be a reef aquarium and would not be unappealing if it resembled one. Most all of the fish offered within the aquarium hobby originate from or near coral reefs. Creating a reef-like structure in a FOWLR style aquarium seems to be a natural thing to do. We recommend replicating these natural environments as closely as possible. The re-creation of an aquatic ecosystem in another part of the world makes for great conversation when someone asks about your aquarium and will increase your enjoyment of the aquarium hobby.

We will recommend two different styles based on keeping either a peaceful "community aquarium" with smaller fish or keeping the larger aggressive predator fish. A community aquarium for smaller fish will benefit from having larger amounts of rockwork with many caves and overhangs that the fish can populate. The larger predator fish will benefit from a more open design with sufficient swimming space and several structures for individual fish to claim territory.

Two styles of FOWLR aquarium Habitat

Central style structure with caves and overhangs.

Bay style structure with separate territories and more open swim space.

Substrate
The substrate should consist of a layer of medium grade (1-2 mm) reef sand (aragonite). You will need enough sand to create about a 2” deep sand bed. The sand bed will also need to be seeded with live sand pre-colonized with nitrifying bacteria.

Water Chemistry

The water chemistry needs to closely resemble that of natural seawater. Here are the recommended water parameters for a FOWLR aquarium:

• Temperature 76-78 F
• PH 8.1-8.3
• Specific Gravity 1.021 –1.023

Hydrometers

Salt Mixes
There are several saltwater mixes available that are great for mixing synthetic seawater. Here are the salt mixes that we recommend.

Instant Ocean

Tropic Marin

Test Kits
There are other parameters that need to be measured occasionally. These include Ammonia, Nitrite and Nitrate. These are important to measure during aquarium cycling and also when there is a problem with the fish. Follow the directions on the test kits for measuring these water parameters

Instant Ocean Master Test Kit

Supplements
If you are using a protein skimmer on your aquarium it may be necessary to add trace elements to your water in between water changes.

Saltwater Additives

Setup

This chart is a timeline describing step-by-step setup of your FOWLR aquarium. After the chart is an explanation of each step.

Choose Location
After you have researched the species of fish you plan to keep and collected all the components you need to set up your FOWLR saltwater aquarium you can begin to assemble the system. Choose a good spot for your aquarium that is not too close to a window or an air vent. Direct sunlight can cause the aquarium to heat up to dangerous temperatures very quickly and also can cause excessive algae growth. Be sure to leave enough space behind the aquarium for equipment and check for clearance from the wall. Check the aquarium with a bubble level. Adjust the stand to level with shims if necessary. Leveling the stand in this way will reduce stress on the aquarium and help avoid leaks. You will also want to make sure that the flooring will support the weight of a full aquarium. Aquariums can weigh as much as 10-12 Lbs per gallon when full not including any rocks or sand!

Take a moment to thoroughly clean the aquarium’s glass using only freshwater and a new clean sponge. This will remove any dust or residue on the aquarium.

Wet Test
It is a good idea to do a “wet test” with all your equipment. You will need to fill the aquarium with tap water and check the aquarium for any leaks. Better to find any potential equipment problems now than later. Install the Wet-Dry (with return pump), protein skimmer, heater, lights and other equipment according to the manufacturers instructions. Connect the overflow from the aquarium, the return pump and connect the hoses to the aquarium. Plug all the electrical equipment into a grounded power strip. We recommend the use of a GFCI (Ground Fault Circuit Interrupt) outlet to prevent any electrical mishaps. This will help protect you and your aquatic pets!

Typical FOWLR aquarium setup showing equipment placement.

Check to make sure you overflow and sump are filled and primed. Plug in the power strip and check the function of all of your equipment. Check that the return pump is flowing properly, the lights are working and that the heater is doing its job as well.

As an alternative you can place your heater and thermometer probe in the sump area of your wet-dry filter. This will allow the same heating and temperature maintenance of your water and remove some equipment from view in the main setup.

Note that the protein skimmer will probably not produce any foam but it is still a good idea to hook it up to check the pump. You will want to run everything for about 24 hours as this will also serve to clean the equipment a bit before you actually set everything up. After your done with the ‘wet test” turn all of the equipment off in the aquarium and drain out the tap water and unplug everything. Be sure and empty the water out of the refugium as well.

Mixing the saltwater
You will need to purchase a large container such as a 20 gallon plastic trash can for mixing your saltwater. You will also need to use your powerhead and heater while mixing the saltwater. You may need to purchase an extra one of each of these pieces of equipment for mixing after your aquarium is setup. It is also good to have an extra power head and heater in case the units on your aquarium fail.

We recommend the use of RO/DI water for the basis of your saltwater mix. The use of RO/DI water will eliminate a larger number of problems that can normally arise from the use of tap water. Tap water contains many impurities and contaminants that are not suitable for many saltwater species. Large amounts of phosphates and silicates in tap water can contribute to nuisance algae blooms.

RO/DI water can be purchased from your grocery store pre-bottled or from a vending machine. Local fish stores may also sell RO/DI water. Another option is to get your own RO/DI unit. If you plan on being a saltwater aquarium hobbyist for any length of time then a RO/DI unit is a great investment.

Fill the mixing bucket with a known amount of RO/DI water. You may want to mark off the sides of your bucket by filling a gallon jug, pouring it in the bucket and marking the outside of the container with a marker. Repeat this process until you have marked the majority of the container with 1 gallon increments.

Add the indicated amount of salt mix (see manufacturers instructions) for the amount of water in the bucket. This is usually about ½ cup per gallon. You can use a large spoon to initially mix the salt. After adding the salt mix drop your powerhead into the bucket and plug it in. Let the powerhead run for about an hour to thoroughly mix the salt.

Preparing the sand
While the saltwater is mixing you can prepare the sand for the aquarium. You will want to use enough sand to create about a 2” deep sand bed. If your sand comes packaged dry it is a good idea to rinse it with some tap water in a 5 gallon bucket. Fill the bucket about 1/3 full of sand, then fill with water and stir. The water will become quite cloudy with the dust from packaging. Let the sand settle for a moment and then dump off the rinse water. Repeat this process a few times until the water becomes less cloudy. Do a final rinse with some RO/DI water.

Finally, add the rinsed sand to the aquarium. Smooth out the sand to create a fairly uniform depth of about 2”.

Adding the saltwater
Test the water for specific gravity using a hydrometer. The specific gravity should be between 1.021-1.023. Adjust the specific gravity if necessary by adding RO/DI water to lower it or by adding salt mix to raise it.

Add your first batch of saltwater to the aquarium by slowly pouring it over a plate to prevent excessive stirring of the sand. You may also add a hose to the return end of your power head to pump the water from the bucket to the aquarium. Immediately start mixing another batch of saltwater as it may take a few batches to completely fill the aquarium.

Aquascaping
While the next batch of saltwater is mixing you can begin to aquascape your aquarium. Be sure to remove any equipment such as glass heaters and filter tubes before you begin aquascaping.

A centered rock structure filling the aquarium's back wall.

There are many types and personal styles of scenes that can be created in the FOWLR aquarium. In this article we will recommend two basic styles that have both function and form. One is the central rock structure with swimming space on each side of the aquarium. The other is the Bay style with structures on each side of the aquarium with open swimming space in the middle.

The main idea is to create an environment that the fish can be comfortable in. The central structure is great for a community style aquarium with the less aggressive species. It can be arranged with cave-like openings and overhangs that fish can hide in and call home. The Bay style with the side structures is a good choice for the more aggressive predator species. These fish require more open swimming space and having the two structures offers more territory for the fish to claim.

Both styles main structures are built from live rock. Live rock is also a primary filtration component for this setup so you will need to select the best quality live rock you can afford. You will need approximately 1 lb of live rock per gallon of aquarium water. This amount will vary with the density of the live rock you select.

Stacking the rocks
Start by building the foundation for your structure. Foundation rocks should be smaller pieces of rock. The goal is to create areas that water can pass through and around the rock while minimizing the amount of the sand bed that you cover. This also creates cave type areas for fish and other creatures to hang out in. These foundation rocks also need to be pushed into the sand so that any digging species that you may add to the aquarium don’t topple the rocks.

The next step is to place the upper rock structure. These can be larger live rock pieces and should be supported by the foundation rocks. Take into consideration the natural upper surfaces of the live rock that need to be facing the light. These surfaces will usually have more coralline algae growth.

Securing the rocks
You need to consider securing the upper rock structure to prevent the rocks from falling over and breaking the aquarium glass. You can use Aqua-Stik to “glue” the rocks together. This is a water friendly epoxy that cures quickly and also comes in either a coralline pink or a gray slate color. Aqua-stik cures under water so the aquarium filled immediately.

Try to avoid placing the Live Rock directly against the glass leaving sufficient room for good water flow. Also remember to leave enough room on the sides and front of the reef structure to allow cleaning the glass with a magnet cleaner.

Seeding the sandbed
Seeding the sandbed with pre-colonized sand from an established saltwater or reef aquarium can give you a head start on cycling the aquarium. You can get some live sand from a fellow hobbyist or purchase one of the pre-colonized mixes available and add it to the top layer of your sand bed after you add the live rock.

Filling the aquarium
Once the sand and live rock have been installed you can fill the rest of the aquarium with the mixed saltwater. Add additional batches of saltwater until the aquarium is filled. Re-install any equipment you removed earlier and power up.

The First 24 Hours
Note that the protein skimmer does not need to be installed until the aquarium has cycled. Some protein skimmers have a pre-filter media basket that can hold carbon and other media. We recommend the use of carbon in this basket. If your skimmer does not have a media basket you may place carbon media in the first compartment of your sump.

After the aquarium has circulated for about 24 hours test the saltwater for the following parameters:

• Temperature 76-78 F
• PH 8.1-8.3
• Specific Gravity 1.021 –1.023

Adjust any of the above that are out of range.

Adding Fish
Once the aquarium is filled, the water parameters are correct and the equipment has run for about 24 hours you may add a couple of fish and start the cycling process. Keep in mind that it usually takes about 4-6 weeks for the aquarium to cycle/stabilize and that patience is key during this process. You will be able to add more fish after the cycle is complete.

Adding too many fish too quickly can be dangerous to the fish. The ideal situation would be to wait approximately two weeks before adding your first fishes. This will allow the aquarium to stabilize and the live rock to establish. For more information on the Nitrogen Cycle read our article on Cycling Your Aquarium.

Species

There are many beautiful fish that can be kept in the FOWLR aquarium. We will make a few recommendations of different fish. Be sure to familiarize yourself with the requirements and behavior of the various marine fish before you purchase them.

Community Species

Clownfish Amphiprion ocellaris Temper: Semi-aggressive Adult size: 2.5 in Feeding: Omnivore Not required but does well with Anemone’s. Sometimes available as a mated pair.

Pajama Cardinalfish Sphaeramia nematoptera Temper: Peaceful Adult size: 3 in Feeding: Carnivore Shoaling fish that can be kept in groups in larger aquariums (50g and up).

Green Chromis Chromis viridis Temper: Peaceful Adult size: 2.75 in Feeding: Omnivore Shoaling fish that can be kept in groups in larger aquariums (50g and up). Good starter fish.

Coral Beauty Angelfish Centropyge bispinosa Temper: Semi-agressive Adult size: 4 in Feeding: Omnivore Only keep one of this fish. Requires an established aquarium.

Aggressive Species

Harlequin Tuskfish Lienardella fasciata Temper: Semi-Agressive Adult size: 7 in Feeding: Carnivore Requires a large aquarium (75g) with ample swimming room. Only keep one of this fish.

Picasso Triggerfish Rhinecanthus aculeatus Temper: Aggressive Adult size: 9 in Feeding: Carnivore Requires a large aquarium (75g) with ample swimming room. Only keep one of this fish. Warning: Very sharp teeth!

Lyretail Wrasse Thalassoma lunare Temper: Aggressive Adult size: 6 in Feeding: Carnivore Active swimmer requiring lots of space.

Lionfish Pterois volitans Temper: Semi-Aggressive Adult size: 8 in Feeding: Carnivore Predator species that will eat other small fish. Warning: Has venomous fins!

Stocking
There are two methods for calculating the number of fish you keep in a saltwater aquarium. The first method uses the total water surface of the aquarium to determine stocking levels. This is based on the adult size of the fish in inches. We recommend 1 inch (body length) of fish per 36 sq. in of water surface.

Here is a reference chart for determining stocking levels based on water surface:

Another method is to base it on total aquarium volume. Recommendations of ½” of adult fish per gallon are common.

Here is a reference chart for determining stocking levels based on aquarium volume:

As you can see there is a big difference between the two methods. The second method recommends that you can keep many more fish in the same size aquarium. This can cause problems with the increased bio-load on the aquarium. This can also lead to conditions that can be unhealthy and stressful for the fish unless strict maintenance is done on a consistent basis.

We recommend a stocking level closer to the first method based on water surface. This method takes into consideration the oxygen exchange capability of the aquarium. This is an important factor in keeping your fish healthy.

Some other things to remember when stocking your FOWLR aquarium:

• Know the adult size, temper and feeding requirements of the fish you are purchasing.
• Try to stock the smaller less aggressive species first allowing them to establish territory before adding the aggressive species.
• Be aware that some species can be dangerous to the hobbyist. Tangs have sharp spines and Lionfish are venomous.
• Do not add aggressive fish such as Damselfish as the first inhabitants. Consider Green Chromis or other peaceful species as an alternative.
• Stock gradually by adding only 1 –2 fish per month

Feeding

To feed your fish properly you need to know whether your fish are omnivores (plants and meat eaters), herbivores (plant eaters) or carnivores (meat eaters). Your fish also need to eat a varied diet so they get all the proper nutrients to maintain good health. It is not recommended to just get a can of flake food for your fish’s only meal. Here are a few recommended diets for your fish.

Maintenance

A little bit of maintenance done on a regular basis will go a long way to keeping your aquarium healthy.

Water Changes
Water changes are the basis for successful aquarium keeping! This is the easiest thing you can do as an aquarium owner to maintain a healthy environment for your aquatic pets. Water changes help to remove high concentrations of contaminants and replenish lost trace elements. You will need a few basic pieces of equipment including a large, clean plastic bucket, a gravel vacuum, a thermometer, a hydrometer and salt mix.

You should change about 10% of the water in the aquarium about twice a month. A good way to remember is to do water changes on the 15th and 30th day of each month.

Follow the directions above to mix up your replacement saltwater before you start your water change. In a 50 gallon aquarium you will need to change about 5 gallons of water. Your 20 gallon plastic trash can will come in very handy for water changes.

We recommend that you use RO/DI water as the basis for your saltwater mix. Add the indicated amount of salt mix (see manufacturers instructions) for the amount of water in the bucket. This is usually about ½ cup per gallon. You can use a large spoon to initially mix the salt. After adding the salt mix drop your extra powerhead into the bucket and plug it in. Add a heater if necessary to bring the temp up to the 76-78F range. Let the powerhead run overnight to thoroughly mix the salt.

Test the water for specific gravity using a hydrometer. The specific gravity should be between 1.021-1.023 and should match the specific gravity of the aquarium water. Adjust the specific gravity if necessary by adding RO/DI water to lower it or by adding salt mix to raise it.

Remove the necessary amount of water from your aquarium (5 gallons in this example). At every other water change you should use a gravel vacuum to carefully siphon any detritus off the rocks and sand. When siphoning the sand you may need to pinch the hose of the gravel vacuum so that it is just strong enough to remove any waste on the surface but not so strong as to siphon up the sand itself.

Add the new saltwater into the aquarium. You can attach a hose to the end of your power head to pump the water into the aquarium.

Skimmer Maintenance
Empty your skimmer cup as it becomes filled. Follow the manufacturers directions for regular skimmer maintenance including periodic cleaning of the pumps and impellers.

Sump Maintenance
The overflow foam prefilter should be rinsed out with aquarium water at every water change and at least once a week. Any other foam media in the filter should also be rinsed weekly or removed completely. For best results replace the foam media every 6-8 weeks. The bio media should not be cleaned unless absolutely necessary and then only half at each cleaning. The return pump from your wet-dry will need to be taken apart and cleaned about every 3-4 months. More often if there are problems with noise or reduced flow in the aquarium.

Top-off
It will be necessary to top-off the aquarium with freshwater to makeup for evaporation. Be sure to use only fresh RO/DI water as the salt does not evaporate. Test your specific gravity periodically for consistency after top-off.

Cleaning the Glass
The inside of the glass will begin to grow various types of algae and will require occasional cleaning. Use a magnet cleaner to keep the inside glass sparkling clear. Some hobbyists only clean the sides and front glass and let the back glass get covered with coralline algae and other natural growths.

You may also need to clean the outside of the glass to remove fingerprints and other residue. Use a clean paper towel with freshwater to clean the outside glass. If the outside glass gets excessively dirty you may use glass cleaner to clean it. Be extremely careful when using glass cleaner. Do not spray the cleaner directly onto the aquarium glass. Spray a paper towel, away from the aquarium, and then wipe the glass clean. It is also a good idea to wipe the aquarium down with freshwater to remove any leftover glass cleaner residue.

Salt Creep
This is the crusty deposit leftover on the rim of the aquarium and around the light fixture from saltwater evaporation. The salt does not evaporate and will leave this crust on areas that get splashed with aquarium water. The best way to clean this residue is too use fresh water on a clean paper towel. Never use any cleaning chemicals to clean salt creep.

Other Information

For more information on the FOWLR and other saltwater aquariums take a look at these great books.

Books
The New Marine Aquarium: Step-By-Step Setup & Stocking Guide
By Michael S. Paletta

The Conscientious Marine Aquarist: A Commonsense Handbook for Successful Saltwater Hobbyists
By Robert Fenner

Marine Fishes: 500+ Essential-To-Know Aquarium Species
By Scott W. Michael