aquaria

Marine Aquaria in Bermuda

Ralph Gonzalez

05/01/2002

Bermuda is a fortuitous place for aquarium hobbyists. It is possible to make frequent water changes using ocean water, reducing the cost and work normally required to maintain good water quality. Furthermore, a snorkeling expedition can yield numerous fascinating species of fish and invertebrates suitable to the aquarium environment.

Here are a few notes on maintaining salt-water aquariums in Bermuda. They are intended for the hobbyist with 10-100 gallon tanks.

Water Quality

The single most critical item in a marine aquarium is water quality. Water quality involves animal wastes, salinity, minerals, etc. Filters and beneficial bacteria help maintain good water quality but it is imperative to do partial water changes weekly to prevent a buildup of toxins which the filters are ineffective to, and to replace minerals.

Insufficient attention to water quality can lead to a cycle of death:

First some of the more sensitive inhabitants (such as sponges) will die off. Their decomposing bodies pollute the water causing less sensitive animals to die. Their bodies, in turn, further pollute the water until the entire tank is dead.

The good news is that in Bermuda the availability of fresh ocean water can greatly simplify maintaining water quality and reduces the need for expensive filtration and test equipment.

Water Changes

In Bermuda we have the luxury of being able to use actual ocean water when performing a water change. This eliminates the need for expensive ocean salt mixes and allows the hobbyist to dispense with test kits for Ph, salinity, minerals, etc.

Before doing a water change, top off the aquarium with fresh tap water to replace that lost by evaporation. (Don't use salt water to top off, because no salt is lost to evaporation.)
Replace 10-20% weekly. If you don't stick to a schedule, toxins will build up, leading to the cycle of death.
Use 1/2" tubing to siphon water out of the tank. Clean the sand/gravel at the bottom of the tank at this point, using a large-diameter gravel-cleaner attachment.
While you're at it, use a non-abrasive mesh kitchen sponge to clean the front pane of your tank.
Some recommend that you leave newly-collected ocean water in a closet for a week before adding to your tank as a quarantine measure to kill parasites. I'm not sure this is really effective. Moreover, I think this will also kill potentially nutritional microorganisms in the water. Parasites are always present in the marine environment and the best way to protect your fish is to keep them healthy and well-fed so they can fight off parasites themselves.

I find it convenient to use 3-gallon Pure Water jugs, filled at the steps of the nearest dock.

Filtration

There is an overwhelming variety of filters available to marine aquarists. There are also many philosophies on filtration. If you make regular water changes using ocean water, filtration requirements are less stringent and a simpler is better philosophy is possible:

The extreme approach is embodied by some of the older tanks at the Bermuda Aquarium, Museum, and Zoo. Water is continually pumped in/out of these tanks directly from the ocean, after passing through a sand filter.

Biological Filtration. The first defense against the build-up of water toxins is actually provided by living organisms in the tank: beneficial bacterial colonies. Once these bacteria are established, they convert harmful ammonia into more tolerable nitrates. A number of filters offer an environment in which these bacteria can thrive. However, living rock - in addition to harboring attractive invertebrates and providing refuge for fish - can hold sizeable colonies of beneficial bacteria: the rock becomes the biological filter. The only caution is to add fish to the tank over a period of time as the bacteria levels slowly rise.

Protein Skimmers. In the presence of marine invertebrates (anemonae, sponge, etc), an effective and reliable protein skimmer is neccessary to prevent build-up of harmful wastes and excessive nutrients (which promote unwanted algae growth). A protein skimmer produces fine bubbles to which waterborne proteins attach. The resulting foam is "skimmed" into a collection cup, producing a dark liquid which you empty weekly.

Inexpensive in-tank and hang-on models are available. Unfortunately if you don't clean them regularly they will silently lose effectiveness and your water quality will quickly degrade. Therefore I strongly recommend you purchase one of the following high-quality and low-maintenance units (though there are probably several others I am not aware of):

CPR Bak Pak. Up to 60-gallon tanks, about $120-$130.
US Aquarium Bioskim 600. Up to 75 gallons, about $130-$150.
AquaC Remora. Up to 75 gallons, about $160. (Highly efficient and effective.)

You must still clean the skimmer's powerhead every few months to ensure proper water and air flow. Keep a wary eye on the rate of foam production.

If your tank contains an effective protein skimmer and bacteria-harboring living rock, and you regularly change the water and clean up detritus on the tank bottom with a gravel-cleaner siphon, you may find that no further filtration is neccessary.

Mechanical/Chemical Filtration. It may also be useful to add a simple power filter with easily-changed polyfill to remove suspended particles in the water. You may need to switch the filter off during feeding. A charcoal bag in the filter also slows the buildup of toxins, if you remember to change it regularly.

Water Flow. A good powerhead should be used to provide water flow in the marine aquarium. Many invertebrates depend on water flow for feeding. Surface agitation by the powerhead helps reduce surface "scum" which can otherwise inhibit water oxygenation and promote harmful bacteria.

Bacteria

Many books stress the importance of a break-in period during which beneficial bacteria colonies become established in a new tank to create the nitrogen cycle:

Fish food and fish waste become toxic ammonia and can quickly lead to the demise of life in the aquarium (cycle of death), as decomposing organisms further contribute to ammonia build-up. Nitrosomonas bacteria, once present in the tank, convert ammonia into nitrite. Another group of bacteria, Nitrobacter, are required to convert nitrite into less harmful nitrate.

Fortunately, if you start your tank with ocean water and/or add sand or rocks from the ocean, then your tank already has these bacteria present. Moreover, sand and rocks will harbor these bacteria so that expensive add-on bacterial filters are superfluous. The only caveat is to add fish to the tank over time to allow the bacteria populations to establish themselves.

Though harmless in small concentrations, a steady build-up of nitrates in the tank will eventually kill fish. Therefore, water changes are an integral part of the aquarium nitrogen cycle.

Lighting

A fish-only tank is not very sensitive to light quality. But if you include rocks with living anemonae, sponges, etc (a "mini-reef" tank), aquarium lighting is critical. Insufficient or wrong-wavelength lighting will cause many sponges and anemonae to die, compromising water quality and potentially harming your fish!

Most anemonae and corals house algae, which provide the animals with their coloration. This symbiotic relationship supplies sustenance to the anemonae. Without proper lighting, the algae will die and the anemonae will turn white and will slowly lose mass and die.

Spectrum. Since water filters out most of the red end of the spectrum (that's why underwater photos are blueish), these algae have developed to require blue-shifted light. Actinic fluorescent bulbs supply this portion of the spectrum. I've found 50/50 (50% daylight, 50% actinic) bulbs to provide bright, healthy, and attractive lighting. Hagen PowerGlo bulbs will also do (the yellowish LifeGlo model is neither attractive nor effective in a marine aquarium). Halogen bulbs are another option, though these are expensive and more difficult to come by.

Brightness. A single fluorescent bulb will usually not begin to approximate daytime light levels. Unless you have a lux meter, you'll have to use your judgement and trial-and-error to determine the number of bulbs required to maintain invertebrate health. Most successful tanks use two to four parallel full-length fluorescent bulbs. Unwanted algae may develop in a bright tank, unless nutrient levels are kept low via proper filtration.

Bulb Changes. The spectra of fluorescent bulbs shifts over time. A good rule of thumb is to replace such bulbs every 6 months regardless of their perceived performance. As the light spectrum shifts, you may otherwise experience excessive algae buildup and see the health of your invertebrates decline.

Rocks

It is not permissible in Bermuda to collect corals nor to chisel "living rock" from the reefs. You may collect loose rocks which contain no corals. This is very tempting because local rocks are encrusted with living sponges, anemonae, algae, tubeworms, etc.

The result of introducing a large living rock to your tank is often disastrous, however. The reason is that no matter how good your lighting and filtration/water change frequency, the tank environment simply cannot support some of the more sensitive forms of life on the rock. Decomposing sponges can seriously compromise your tank's water quality and can cause the aforementioned cycle of death.

Introduce living rocks in small quantites and take note of which sponges, algae, and anemonae are still present 2 months later.

Substrate. Coarse gravel is preferred to sand as it is easier to keep clean using a gravel-cleaner siphon attachment. This substrate should be kept shallow to avoid harboring harmful anaerobic bacteria.

Fish

Some aquarists avoid fish because they may interfere with marine invertebrates. There is no denying, however, that well-chosen fish add interesting color and dynamics to your tank.

In choosing fish, there are two things to consider: how hardy is the species, and how well does it interact with the rest of the tank? A few observations I've made are:

Butterflyfish. Attractive buy not very hardy. They also will nip at colonial anemonae causing them to refuse to open.
Angelfish. Attractive and a bit hardier, though picky eaters. Be aware that some angels will eventually outgrow all but the largest tanks.
Doctor/Surgeonfish, Tangs. Slim profile means they must eat continually. Prone to illness. Not recommended.
Puffers. Good eaters but not ultimately hardy.
Damsels/Cow Polly. Many attractive varieties. Quite hardy though highly territorial.
Wrasses. Many attractive varieties. Quite hardy and fairly tolerant of other species.
Gobies. Very hardy.
Seahorses. (Invertebrate?). Easy to catch around boat lines. Very difficult to care for, require live feeding.

Wrasses and Damsels are probably the best choice among local Bermuda fish unless you are prepared to invest some effort. Be careful to introduce fish to the tank over time as the beneficial bacterial colonies become established. Also avoid overloading the tank with too many or too large fish. On the other hand I've found that very small juvenile fish (1/2" long) are less hardy than larger specimens, perhaps because they require more frequent feedings.

Collecting fish. You will find it extremely difficult to catch the speedier fish with an aquarium net. They often swim tantalizingly close to the netting but it is impossible to "sweep" these fine-mesh nets through the water fast enough to scoop the fish up. Look for a monofilament net made for collecting small fish in the wild. Locally you can try Making Waves on Front Street. A two-net approach is often effective.

Feeding. I generally use frozen brine shrimp, frozen bloodworms, flakes, and - for larger fish - pieces of frozen bait squid. Be careful not to overfeed, introducing unneccessary waste material to your water. On the other hand, underfed fish are more likely to aquire parasites and disease. One feeding a day is sufficient for most fish.

Invertebrates

These include anemonae, corals (not permitted in Bermuda), sponges, as well as crabs, shrimp, shellfish. Avoid introducing species which are likely to die, compromising your water quality. A few observations:

Corals. It is illegal in Bermuda to collect or keep corals. This includes soft corals such as sea-fans and sea-rods.
Anemonae. A very colorful and varied addition to tank. Require good lighting. Take care removing from rocks or - preferably - collect the rock itself. Try the blue/green Sea Mat (colonies of small, brightly-colored anemonae) and the hardy Mermaid's Hair.
Sponges. Many can't survive in an aquarium due to insufficient lighting, water quality, and/or lack of water-borne nutrients. I've had success with Golfball sponge and some gray and black species.
Sea Urchins. Interesting but tend to rearrange anything not tied down in your tank, and will slowly turn your rocks into sand.
Snails. Useful and hardy.
Sea slugs. Tiger-striped slugs are lovely but require a steady supply of purple sponge. Sea Hares are fascinating and can survive on Romaine lettuce (though their preferred diet is red algae).
Crabs. Hermit crabs are interesting and generally harmless. Other crabs can be predatory and are difficult to remove once introduced.
Shrimp. Mantis shrimp are fascinating but highly predatory and nearly impossible to eliminate. Glass shrimp are hardy, unless you have hungry fish in the tank. Banded Coral shrimp are attractive, though difficult to find.
Jellyfish. Even if you find a small specimen which doesn't bother the other inhabitants, it is likely to quickly fall victim to the filter/powerhead intake tube.

Feeding. Colonial anemonae and sponges generally fare well with sufficient lighting and nutrients present in the water. Try to place them where there is good water flow. Larger anemonae benefit from direct feeding of frozen brine shrimp or almost any food. Most of the remaining invertebrates scavange for leftover food particles and don't require direct care.

Legalities

Call the Bermuda Department of Agriculture and Fisheries for information on permits and rules for collecting fish. It is not permissible to employ scuba gear when collecting fish, and there are a number of protected reserves around Bermuda. There are also numerous protected species including scallops and clams, lobsters, hogfish, etc.

Resources

I've barely scratched the surface of the information available to marine aquarists. A web search will quickly locate detailed information on filtration, lighting, and many other relevant issues. Below are a few resources for the Bermuda-based hobbyist.

Check out the Bermuda Marine Aquarium Club forum for contact information, equipment, meetings, and a place to exchange notes.
The people at the Bermuda Aquarium, Museum and Zoo are usually happy to provide suggestions on care for specific marine species.
Local aquarists will find Wolfgang Sterrer's, "Bermuda's Marine Life", completely indispensible. It provides hints on feeding for a large selection of interesting local species.
Pic-A-Pet and Noah's Ark are local sources for frozen Brine shrimp, fluorescent bulbs, tanks, etc. As expected, they may not stock specific items.
Making Waves on Front Street sometimes stocks collecting nets and has snorkeling apparatus.
That Fish Place is a well-stocked mailorder warehouse which ships to Bermuda. Marine Depot is another excellent source.

Thanks to Craig Morfitt for help preparing this document.

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