Your E-mail:
Get the latest news, tips and
free advice every month
Fish Species at

Printer Friendly Bookmark and Share

Join the Marines - Part Two

Setting up and stocking the tank.

By Nick Dakin

You visit four different dealers with the same question, you will likely get four different answers, which will confuse matters considerably. Marine fishkeeping is not an absolute science, and it may well be that all four store owners are correct in their opinions. Not very helpful to the novice, I admit, so try to stick with the dealer who is helpful, friendly, has the best stock and will be supportive should things go wrong.

Do not just search for goods at rock-bottom prices. Why should a knowledgeable dealer help you for free if you have bought all your equipment elsewhere? A reliable and honest retailer is worth his or her weight in gold.

Setting Up
We will assume the tank already contains an undergravel filter and rockwork, as discussed last time. Once all the electrical hardware (powerhead, heater, lights) has been neatly wired, preferably positioned within one of the cabinet cupboards for neatness, the tank can be filled with tap water to about three-quarters of capacity.

The chemistry of tap water varies in many areas, so the marine fishkeeper may decide to pre-filter the water through a nitrate-removing resin. These resins can often be re-charged many times and used for considerable periods. Deionizers also use resins and perform a much more efficient job. However, only limited quantities of water can be collected before the resin requires re-charging or replacing, which can prove expensive.

If your budget allows, installation of a reverse-osmosis unit can be a very helpful, particularly if invertebrates are to be kept at a later date. This is not to imply that the use of reverse osmosis water will not aid fish as well — it will. Health, color, appetite and vitality will all benefit greatly.

Marine Fish

Cardinals — quiet, inactive, easy to keep. An ideal choice.

Gobies — peaceful, easy to feed. Smaller species may need a "quiet" tank, others may dig, disturbing substrate and rockwork.

Hawkfish/Firefish — Usually peaceful and interesting, but largely inactive.

Dwarf Wrasse — active, mostly peaceful fish that are easily fed.

Dwarf Angels — colorful, mostly peaceful fish. Keep only one in a tank.

Blennies — interesting fish, easy to feed, but can be territorial.

Clownfish — very colorful, good community fish, but intolerant of poor water quality. Some species seem to do poorly without an anemone.

Tangs — active and colorful, but are prone to common parasitic diseases.

Grammas — can be very territorial and aggressive. Very colorful. Some species may be shy and need special attention to get them to feed.

Damsels — can be very territorial and bullies, but are easy to feed and colorful. Introduce last, if possible.

Some species that are definitely best avoided at this stage include large angels, triggerfish, mandarinfish, parrotfish, morays, batfish, butterflyfish, lionfish, groupers, seahorses and pufferfish.

Pumps and heater, but not the protein skimmer or canister filter, can now be switched on and left to bring the water up to an operating temperature of about 77 degrees Fahrenheit. This should take about 24 hours. Once the desired temperature has been reached, a good quality salt mix can now be slowly added until the specific gravity reaches 1.021. This is a comfortable and practical level for most fish, as well as being cost-effective for the fishkeeper.

Many people will be aware that specific gravity is measured using an hydrometer, of which two types are in common usage: floating and swing needle. Of these, the swing needle version is the easiest to read, but more expensive than the floating type, and not necessarily as accurate over the long term.

Once the salt has been added, the water level should have risen to the required point. Re-check the specific gravity, and add more water or salt as needed. Leave for another 24 hours and re-check both the specific gravity and temperature once again.

There are a number of ways to start the biological cycle that is so vital to the operation of the aquarium. Some aquarists use fish that the dealer will often take back for credit once the tank is broken in (more on this later). Other hobbyists choose to use pure household ammonia, and still others choose a proprietary starter product for this purpose.

Regardless of the exact procedure, ammonia and nitrite levels in the tank water can be expected to reach a peak, and then as the nitrifying bacteria begin to multiply, the levels will begin to drop until zero readings are obtained using the appropriate test kits (inexpensive but very important to use). The whole process should take between 21 and 28 days on average.

During this period the pH may drop slightly, but should remain somewhere between 8.1 and 8.3. Some aquarists advocate the "seeding" of a new aquarium with substrate from a mature tank. This may speed the maturation process up by a few days, but it can also spread diseases and other unwanted organisms into an otherwise safe tank.

Regarding the break-in process in which fish are used, in my opinion this method is usually adopted by the impatient hobbyist or uncaring dealer desperate for a fish sale. So-called "hardy" fish, usually damsels, are introduced into the tank on the first day. The fish have to then endure very high levels of ammonia and nitrite until the bacterial bed is mature. This practice not only stresses the fish, leading to disease and sometimes death, but it also poses an extra problem for the aquarist.

After a few weeks in an aquarium, damsels tend to become very territorial, and any additional fish will usually be attacked, causing unnecessary stress and a high probability of disease outbreak. Even if the dealer is prepared to take the fish back, why should we subject what we consider to be our pets to such an ordeal? Conscientious fishkeepers and dealers avoid such practices and use more caring methods instead.

Technology has provided us with living bacteria to add straight into the tank. Instant biological maturation should be the result, but experience has shown varying degrees of success. My advice is to add living bacteria if desired, but test their effectiveness by introducing a largish dose of the product.

If, after dosing the tank with pure (no colors or perfumes) household ammonia to about 10 milligrams per liter (determined with ammonia test kit), and having added the bacteria product, the ammonia and nitrite test kits reveal zero readings when taken six to 12 hours later, then it has worked. If, on the other hand, levels are still high, then the bacteria have failed to establish and the original maturation process will have to be continued.

Once the biological filter begins to mature, it will frequently be observed that a light dusting of brown algae covers the rockwork, decoration, substrate, tank sides and just about everything else. It is a common species of algae that often makes a brief appearance at this stage in an aquarium's life. It thrives on nutrients found in brand new tank water. Once these nutrients are exhausted, the algae disappear. The cycle can take from one to three weeks, and though unsightly, need not prevent stocking of the tank.

Anyone with a knowledge of elementary science will be aware that a body of water open to the atmosphere will be subject to evaporation. Only water molecules evaporate — salts and solids remain behind to make the solution progressively more dense. Aquariums are no exception.

Water molecules evaporate constantly, and the specific gravity will continue to rise. Or at least it would do so if we did not replace the water lost.

After the initial filling, the water level can be marked with a pen or sticker. Evaporated water can be replaced by fresh tap water every two days back up to this mark.

Tank Maintenance


  • Check temperature
  • Observe fish
  • Remove uneaten food
  • Remove protein skimmer waste
  • Check for signs of disease

    Every Two Days:

  • Top up evaporated water
  • Clean algae from front glass


  • Clean tank and cover glass
  • Add trace elements, pH buffers and vitamin supplements if considered necessary

    Every Two Weeks:

  • Change 10 to 20 percent of water
  • Test for ammonia, nitrite, nitrate and specific gravity (more often in new tanks)


  • Rake through substrate to prevent clogging
  • Siphon off mulm

    Every Two Months:

  • Replace protein skimmer diffuser
  • Clean out protein skimmer
  • Change carbon
  • Remove unwanted algae (more often if required)

    Glossary of Terms

    pH — A measurement of the acidity/alkalinity of water on a scale of 0 to 14, with 0 being extremely acid and 14 being extremely alkaline. Seawater is reasonably alkaline and usually stable throughout the world at 8.3.

    Specific Gravity — A measurement of how much salt the water contains. Distilled water is 1.000, seawater is usually around 1.021 to 1.026.

    Ammonia and Nitrite — Nitrogenous toxins produced directly as waste (ammonia) by fish. Converted by nitrifying bacteria in the biological filter into toxic nitrite and then relatively harmless nitrate (removed by water changes). Ammonia and nitrite are highly toxic to fish and invertebrates, leading quickly to disease or death.

    Buffering — In which calcareous rocks or liquids are used to combat the natural tendency of the tank water to acidify, thereby reducing the pH.

    Activated Carbon — Specially treated carbon designed for marine use. Much more effective than freshwater grades.

  • Stocking Levels
    When ammonia and nitrite tests result in readings of zero, the tank is now considered to be mature and ready for its first residents. Sensible stocking levels have always been one of the keys to the successful aquarium. Overstocking and stocking too quickly are two of the major causes of stress, leading to disease and untimely deaths.

    This fact was quickly realized by the early pioneers of the hobby, and they devised some basic guidelines that largely hold true today. The formula for most aquariums is 1 inch of fish for every 5 gallons of water for the first six months. After a year, this level can rise to 1 inch of fish for every 2.5 gallons of water. This arrangement always presupposes that the aquarium is to be stocked slowly — say, one or two smallish fish every month. Do not expect that a 36-gallon tank can suddenly become home to a 15-inch moray eel with little or no ill effects!

    Mind you, these are maximum levels of stocking. One can never go wrong by taking a more modest approach.

    Plan Ahead
    Generally speaking, small fish require small territories, with the opposite being true for large fish. Therefore, a 20- to 40-gallon tank is more suited to a community of small fish, and our fish plan will reflect this. Not only does this give us the chance to introduce a wide range of species, but it also reduces the possibility of overstocking.

    Always introduce the least aggressive and non-territorial species first. As a result, quieter fish are less likely to be harassed by established inhabitants and are able to settle in a stress-free environment. This is not to say that even the quietest of fish will not resent a new tankmate, but this is likely to be a less stressful ordeal for a slightly more confident species.

    After you have visited a number of stores to see what is available, refer to a few aquarium books on marine fish to understand the character of each species. A plan for stocking can be made accordingly. To help with this process, I have included a basic list of recommended species to be considered by the newcomer (see sidebar entitled "Recommended Marine Fish"). They are also placed in preferred order of introduction in the aquarium.

    Feeding most of the recommended species should present no problem whatsoever. Most will take frozen brine shrimp and mysid shrimp, as well as marine flakes. Live brine shrimp once a week would be a special treat and very beneficial to health.

    Overfeeding can be a real problem in the marine aquarium, and should be avoided completely. One or two light feedings each day is perfectly adequate. All the food should be consumed in about two to three minutes.

    Aquarium maintenance should not be seen as a chore, but a chance to renew, refresh and revitalize. It is absolutely essential to all marine aquariums. The size of tank we have in mind should consume no more than about an hour every two weeks, and a few minutes or so each day just to feed, check the temperature and perform a livestock head count, as well as monitoring for possible early signs of disease.

    Water changes are vital and must be performed without fail for the long-term success of the tank. Between 10 and 20 percent of the water must be changed every two weeks, starting at the lower figure and increasing as the tank becomes fully stocked. Salt mixed in a large bucket to the same temperature and specific gravity of the main aquarium is not a difficult task, and with practice can be prepared quite quickly. It is worth noting here that some salts, usually the better quality and most expensive, tend to dissolve more readily and save valuable time.

    Guidelines for routine maintenance can be found in the sidebar entitled "Tank Maintenance." It is also very useful to maintain a tank diary/notebook in which to keep a record of all test results, new stock, changes of carbon and so on. This will not only act as a useful reminder, but the short- and long-term progress of the tank can be compared easily without trying to remember the details.

    Why No Invertebrates?
    So far, no mention has been made of introducing any invertebrates. This is not an oversight but a deliberate omission. Most invertebrates require superb water conditions, some demand excellent lighting, and most will only thrive if there very few fish present.

    The clownfish/anemone syndrome is a good example. Clownfish cry out for a host anemone, but anemones are extremely sensitive creatures by comparison and require all the special care just mentioned and much more. Better a reasonably happy clownfish without an anemone than a series of dead or dying anemones!

    It is also worth noting that sooner or later the fish may have to be treated for a particular ailment, and most medications are either uncomfortable for invertebrates or downright lethal, as is the case with copper-based treatments. The presence of invertebrates makes treatment of the fish difficult or impossible.

    A marine aquarium can be a welcome addition to any household, bringing interest and more than a little exotic beauty to brighten up our lives. With a little care and attention both fish and fishkeeper can remain very satisfied for many years.

     Give us your opinion on
    Join the Marines - Part Two

    Submit a Comment   Join Club
    Earn 1,000 points! What's this?

    Zip Code:

    Top Products