FAQ: Beginning Saltwater -- Before Buying Your Fish

The Basic Parameters

So what's different about saltwater versus freshwater? As alluded to above, saltwater fish are more sensitive to changes in their environment. The critical parameters of a saltwater tank are pH, nitrate, salinity, and temperature. During the cycling process, ammonia and nitrite can also be a problem. These elements are not different from those of a freshwater tank, but the degree to which they may stray is vastly different.

The pH of a marine tank is one of the most important parameters. Marine fish and invertebrates are especially sensitive to rapid changes in their pH, so keeping pH fluctuations within 0.2 each day is very critical. All marine creatures like a pH near 8.2, ranging from 8.0 to 8.4. The pH should never drop below 8.0.

The next critical parameter is nitrates. Saltwater fish are more tolerant of higher nitrates than invertebrates (in general), but still like nitrates lower than 20ppm, with less than 5ppm being required for most invertebrates. Reef keepers tend to quote anything higher than 0.5ppm as unacceptable, but this is an unrealistic goal for fish-only or minimal invertebrate tanks.

The next parameter of concern is salinity, or specific gravity. Loosely (very loosely), specific gravity is the amount of salt in the water. Many aquarists treat specific gravity and salinity as one and the same, but technically speaking, they are not. Specific gravity is temperature dependent and salinity is not. Most hydrometers (hydrometers measure specific gravity) are calibrated to read the correct specific gravity at 59F. Since this is a little low for most tanks, hobbyist grade hydrometers are usually temperature corrected to read the correct specific gravity at or around 77F (25C).

In any case, most creatures will acclimate to almost any specific gravity (within reason), so long as it does not vary widely. The specific gravity of a saltwater tank should be around 1.022. It's worth noting that the salinity of natural sea water varies according to location (ocean, to lagoons, to estuaries), ranging anywhere from 1.020 to 1.030. So different fish might be native to different salinities, and may need some time to acclimate to a different salinity.

Finally, the temperature of a saltwater tank is basically the same as a freshwater tank. Anywhere between 75F to 80F (24C - 27C), with 77F (25C) being a good midpoint. Wild temperature variations increase fish stress and invariably lead to disease, so a good heater (or chiller) is a must. As an aside, submersible heaters tend to be preferred over hang on the back kinds. Also, they seem to be somewhat more reliable than the less expensive `clip-on' kind.

Other parameters worth keeping an eye on are alkalinity and calcium. The alkalinity of a saltwater tank is really critical for long term success. Without a decent alkalinity reading, the pH of the tank will drop over time and endanger the lives of your pets. The alkalinity of a saltwater tank should be around 2.5 to 3.5 meq/l.

Calcium is more of a reef keeper's issue than a fish-only tank. However, once you advance and wish to keep invertebrates, monitoring calcium levels becomes a must. Without calcium, and other trace elements, invertebrates can not properly form their exoskeletons and will not survive. Calcium levels should be 400 to 450 ppm Ca++. For more information about adding calcium, see the REEFKEEPERS' FAQ.

Some of the more easier to keep invertebrates, such as shrimps, also need regular supplements of iodine and other trace elements. Most foods will supply the necessary amounts of these elements. However, if you are using a protein skimmer, these elements will be stripped from the water and need to be replaced manually. Once a gain the reefkeeper's FAQ has more information about trace element additions.

The Basic Components

Now that we are comfortable with the basic parameters of a saltwater aquarium, let's look into what is needed to run a successful tank.

The components needed to run a successful saltwater tank depends a lot on who you talk to. You should never operate solely under the advice of one person. For example, many people advocate using under gravel filters for biological filtration. This however, must be tempered with wisdom. A saltwater tank running an under gravel filter (UGF) with minimal circulation will be much more work than a than a system running a wet/dry filter and a couple of powerheads. Wet/Dry filters tend to require less maintenance, as UGF's tend to become clogged over time.

Not to get too buried in details, the basic components of a saltwater tank are the tank, decorations, filtration (including protein skimming), lighting, water, and test kits.

One of the most important decisions in starting a saltwater aquarium will be the size of the tank. The basic rule of thumb is the bigger the better. A larger tank will be easier to control and gives a bit more leeway for mistakes (which are inevitable). The smallest tank for beginners should be no less than 20 gallons, with 55 gallons being even better. For someone versed in fish keeping (i.e., converting from fresh to saltwater), a 10 or 15 gallon tank will work, but is not suggested. In general, fish like long, wide tanks. The more surface area a tank has, the better the gas exchange will be and the happier the fish will be.

Before finalizing on a tank size, remember that fish densities are much lower for saltwater than freshwater. That is, you can not put as many fish in a saltwater tank as you can in a freshwater tank. Putting more than 2 saltwater fish in 10 gallon tank is asking for trouble. A general rule of thumb is 4" (10cm) of small-to-medium fish per 10 gallons, or 2" (5cm) of larger/fast growing fish per 10 gallons. This is just a rough estimate of the number of fish. There is no exact number since finding the stocking density has to take into account the filtration, maintenance, feeding schedule, etc..

Beyond the number of fish you wish to keep, the tank's size will also affect your filtration and lighting choices, both in cost and design. Tanks which are 48 inches (122cm) long are usually cheaper to light because the lamps are more readily available. However, the larger the tank, the more light you will need to provide your inhabitants. Moreover, a larger tank needs efficient filtration to keep the system thriving. A good size tank is around 55 gallons.

As a note, scrutinize hoods carefully. Many of them are designed for 48" tanks, but require two 24" lamps rather than one 48" lamp. (24" lamps are usually more expensive than 48" lamps.)

Once you have decided on a tank, make sure you have a place to put it. The tank should not be in direct sunlight or in an area which is very drafty. Also, make very certain the stand will be capable of holding the weight of the tank, plus substrate, plus rocks, plus water. In total, a 55 gallon tank will probably weigh over 800 pounds.

After selecting the tank, consideration must be given to the substrate. It is best to use a calcareous substrate such as crushed coral or dolomite. These substrates will, at least initially, help buffer the water by adding ions to the buffering system. Generally the substrate should not be so tiny as to get sucked into the filter or pumps, and not so large as to make the tank unsightly. Also, some fish (e.g., Gobies) like smaller grades of substrate over larger ones. Something in the 2-5mm department seems average.

Live sand is one substrate which has recently gained a fair amount of publicity. This technology is really in its infancy and is not recommended for beginners. You can find more information in the ARCHIVE.

After you select a substrate, consider the filtration system you plan to use. Your choice in filtration may impact the amount to substrate you need. A UGF or RUGF filter should have about 2-3" (5cm) of medium grade (2-3mm) substrate covering the filter plate. You do not need substrate when you use non-UGF filters (e.g., hang-on-the-back power filters), but, most people use between a 1/2" to 1" for such tanks. It's interesting to note that too much substrate in a non-UGF system might lead to dead spots, which can kill your inhabitants (a plug for regular gravel cleaning). More detailed information about filtration can be found in the FILTER FAQ.

Next, consider the decorations, of which there are a cornucopia of choices. Dead coral, lava rock, tufa rock, live rock, and many more. Coral pieces are the most popular, but are also some of the most expensive. Lava and tufa rock are inexpensive and may also be stacked to make interesting reef looking tanks. Live rock is one of those buzz words that people like to throw around and one which gets a lot of hype. Live rock is simply rock taken from a reef system which has been populated by many different organisms.

Many aquarist dedicated to fish-only setups are beginning to discover the benefits of having live rock in their system. Live rock produces a more natural environment for the fish and also aids in nitrification and denitrification. This implies that the live rock is more that just a decoration, it is actually part of the filtration system. Although it is difficult to use live rock as the sole source of filtration in a fish-only setup, it certainly can be used effectively to reduce nitrates. The use of live rock in fish-only setups must be closely monitored though. If nutrient levels in the aquarium are high, the live rock will be the first to demonstrate this fact. Live rock in presence of high nutrient levels will grow unhealthy amounts of hair algae, and in some cases, cyanobacteria (slime algae). To avoid outbreaks of plague algaes, a few simple rules must be followed.

First, you must start will high quality live rock; live rock which is highly encrusted in coralline algae. Avoid live rock which already has hair algae growing on it. Regular additions of calcium may also be needed to keep the coralline algae thriving. Next, you need to keep nitrate levels low (~10ppm) and ensure you have nearly undetectable levels of phosphate (~0.02 ppm). Finally, feed sparingly; decomposing food is one of the main avenues for introducing phosphate/nitrate and contributing to alga e problems.

If you plan to add live rock to your system, remember live rock contains living organisms, so they can be killed along with any other organism in your tank. It's a good idea to wait until after the tank is set up before buying live rock. There is no good place to store live rock other than in a circulating tank. Trying to do otherwise will be disastrous and costly. Also, if you are going to put live rock into an established tank, the rock must be cured live rock (for a more detailed discussion of cured live rock, see the REEFKEEPERS' FAQ.

Filtration is covered in detail in its own FAQ, with most of the information being relatively generic and applicable to marine tanks. However, there are certain caveats that should be noted. If you decide to use a UGF, reverse flow setups are better. A RUGF will keep nitrates lower by keeping the substrate cleaner and will aid water movement and circulation.

In addition to good filtration, water movement is a must in saltwater aquaria. Without circulation the system will be unstable and usually tends to grow unhealthy amounts of algae and other undesirables. The easiest way to achieve water movement is to have a powerhead in the tank for circulation. One must be careful though, a medium sized powerhead in a small tank will easily make a tornado- like environment and cause problems for small or slow moving creatures.

One of the best possible filtration systems for a fish-only marine tank is a wet/dry filter. Although commercial setups are fairly expensive, a wet/dry filter can be made very inexpensively at home with little effort. The ARCHIVE has a lot of information about constructing your own W/D filter system (as well as other fish related projects).

Many people advocate wet/dry filters for marine tanks stating they are the only acceptable solution. This is simply not true. Any one of the popular filtration systems may be used for a marine tank. The key to success is providing adequate biological filtration without trapping excess detritus. Trapping detritus produces nitrates and inevitably leads to problem algae outbreaks. Which ever filtration system you choose, be sure to rinse the mechanical filtration media at least once a week. Ideally you should rinse the media in old saltwater from the tank to minimize the disruption of any nitrifying bacteria growing on the media.

A part of filtration which most recently has gained wide spread acceptance is protein skimming, or foam fractionation. Protein skimmers are a must for a decently stocked saltwater tank as they strip dissolved organic particles from the water before they can be converted to nitrates.

There are simply too many models and manufacturers to discuss all of them, but the two basic designs are air-driven and venturi. Air-driven protein skimmers use a wooden or glass airstone to produce bubbles in a column of water. Venturi skimmers use a venturi valve to inject bubbles into the water column. Both air-driven and venturi have co-current and counter-current designs, with counter-current protein skimmers being far superior to co-current models.

In deciding on a protein skimmer, there are some basic things to consider. Air-driven skimmers use airstones which must be replaced on a regular basis (usually every month or so). Additionally, they usually require more maintenance than venturi skimmers to maintain proper skimming. Venturi skimmers on the other hand require very powerful pumps to achieve effective protein skimming. They are usually more expensive than air-driven skimmers as well. Also, any skimmer smaller than 24" should be avoided for heavily loaded tanks.

Whichever type of skimmer you buy, the final cost of the skimmer must not overlook the need for an external water pump and potentially an air pump. A $200 venturi protein skimmer usually doesn't include a $150 high pressure pump; a fact that most people seem to miss the first time around.

With the setup nearly complete, you need to consider your near-term and far-term lighting requirements. If you plan on having a fish-only tank forever, then you only need a single full spectrum bulb. However, if you plan to advance in your hobby and keep more sensitive animals such as anemones, you must carefully select your lighting (and filtration as well). Anemones require very strong, full spectrum lighting, supplemented with actinic blue. The general rule of thumb is a minimum of 3-4 watts per gallon, with the higher values for deeper tanks (greater than 18-24 inches). The standard Perfecto hood will not provide enough light to keep anemones alive (or other light-loving invertebrates for that matter).

For a beginning aquarist, fluorescent lighting is probably the best. Metal halide lighting is really for reef keeping and heavily planted freshwater tanks. In any case, if you want or will need something more than a single lamp, your choices are limited. The best thing to do is to build your own hood with custom lighting, or buy one through mail order. Fish store prices usually preclude aquarists from getting proper lighting.

If you select a custom fluorescent hood, then you will have to choose between normal output (NO), high output (HO) and very high output (VHO). Most people with fish-only tanks stay with NO lamps. Both HO and VHO lamps require special ballasts, are more expensive than NO lamps, and need to be replaced more often (more $$).

One critical item in a saltwater tank that doesn't really fit into any of the above topics is that which sets it apart - the marine salt. There are many different brands of salt on the market, all of them being basically the same. The only difference among them is whether or not they have nitrates and phosphates. Both of these are very bad for aquaria, so salts which have them must be avoided. Good salts include Instant Ocean (IO), IO Reef Crystals, and Coralife. As a note, standard rock salt can not be used as a substitute for marine salt mixes. Rock salt does not contain the important elements that marine creatures need to survive.

To measure the specific gravity of your saltwater you will need a hydrometer. There are two basic types of hydrometers available to hobbyist, the floating kind which usually measures temperature as well, and the plastic kind with a floating arm. It's basically a toss up as to which one to get, but the plastic kind has a larger scale and is easier to read.

The final component needed to run a successful saltwater aquarium is test kits. In order of importance, they are pH, nitrate, phosphate, alkalinity, nitrite, ammonia and Calcium (for reef tanks, the calcium test kit is more important than nitrite and ammonia). A good pH test kit is critical, and an electronic pH monitor is even better. Ammonia and nitrite tests are only needed occasionally after cycling. A nitrate test kit is a good overall test for water quality after the tank becomes established. You should perform a pH test once a week and a nitrate test every two weeks. The other kits are not necessary, but may be needed to solve particular problems or after you advance to more delicate creatures.

Setting Up

The following section briefly explains what you need to do to initially setup your tank.

The first thing you need to do is to place the stand in it's final position. Make sure the stand is level in all direction. Next, place a piece of Styrofoam or rubber on the top of stand where the tank will sit. This eliminates small gaps between the stand and tank reducing pressure points which might cause the tank to crack after being filled. After the stand is positioned, place the tank on the stand. Make sure the tank is level in all directions. Note, a tank that is not level has a great chance of cracking after it is filled.

Where ever you place the tank now is most likely where it will remain for its lifetime. You should never move a tank that has water in it since this is a sure way to crack it.

Once the tank is placed, install the filtration. If it is an UGF, then place the filter plate(s) on the bottom of the tank. If it is a wet/dry, then connect the prefilter and all the hoses.

Prior to adding the substrate, rinse it with plain water until the water runs clear, and then add it to the tank. On top of the substrate arrange the decorations. Now the saltwater may be added. The easiest way to add water to a tank is to place a plate on the substrate and pour the water onto the plate.

When initially setting up your tank it is okay to fill the tank with dechlorinated water and then add the salt mix. However, subsequent water changes need to be premixed. Pre-mixing saltwater is done for two reasons, it gives time for the salt to thoroughly dissolve and also allows the water parameters to stabilize. Adding 10 gallons of freshwater and then an appropriate amount of salt to an established tank is a big mistake (and an excellent way to kill your inhabitants).

One note on making saltwater. The source water you use for mixing is extremely important to the overall success and health of the system. There is more to be said about this later, but for now, realize that tap water probably won't be good enough for your tank.

When all the water is in place, start up the filter system and check for any leaks (of both water and air). Let the tank sit for a day or so to clarify (with the filtration running). Now you can add fish.

How many fish you add for the cycling process depends on the size of the tank and the cycling method you choose. You can cycle a tank without any fish at all. In this case, you add ammonium chloride to simulate fish waste and an initial source of nitrifying bacteria. It is best to get a bacteria culture from an established saltwater tank. This can be in the form of some substrate, old filter media, or some macroalgae such as Caulerpa spp.. Live rocks are also an excellent source of nitrifying bacteria.

If you choose to cycle your tank using fish, which is infinitely more interesting than a tank full of circulating water, the number of fish needed depends on the size of the tank. In any case, two fish are preferable to one. If one fish dies, you will still have one to finish the cycling. Of course the second fish may pass on too. If all the fish die, then you have to remove all the contaminants from the tank and introduce more organisms (read this as start all over).

Cycling doesn't have to be limited to fish though. Crabs and mollusks can also be used. However, since these organisms don't produce much waste, it will take longer to cycle the tank.

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