Saltwater How To

How to successfully choose and setup a saltwater tank

NOTE: As with most ENDEAVORS, there are many ways to set up a saltwater aquarium. The following is not the only way, but the way we most often recommend, based on our experience over the years.

The decision:

Just planning to buy “a saltwater tank” is not enough. Do not buy a tank just because you like the shape, color, or because “it looks like a good (cheap) price”. Decide (to the best of your ability) what type of fish and or creatures you want to keep. Do the graceful movements of live coral intrigue you? Are the interesting antics of invertebrate animals such as shrimps and crabs appealing? Do you envision a tank where the “action” is primarily fish and everything else in the tank is non-living decoration (coral skeletons, etc.)? Will these fish be small, colorful, peaceful fish such as gobies, tangs, dwarf angelfish or active predator fish such as triggers, lionfish and eels.

Contrary to most newcomer’s hopes, you can’t have it all. Chances are (unless you’re starting 3 or more tanks at one time) you’ll have to prioritize your desires.

If you can’t answer this first question, stop here, close this website, and visit your best local fish store armed with paper and pen and questions.

The options:

OK, so now you know (with a good degree of certainty) what you want to keep and what can be kept appropriately in a given tank. Here are two general directions you might pursue:

The reef tank

If you decide that you want to keep live corals and/or anemones, these are best kept in a setup we call a “reef tank.”

Two characteristics of a reef tank that may affect your choice of an aquarium are:

  1. The need to make a “rock pile.”
  2. The need for intense lighting.

A proper reef tank holds a large amount of “structure.” This is typically a wall of rock (preferably “live rock”) upon which one will place assorted invertebrate animals in an attempt to recreate what a coral reef might look like. Never mind that it usually does not look much like the real thing. In practice, this rock pile is really a display shelf for the specimens one acquires. It allows one to place these mostly light-loving specimens at the proper height in the tank, keeps them spaced apart from each other and, hopefully, from falling over.

Envision your “reef” (rock pile) almost the length of the aquarium, sloping from a point at least 4″ from the front glass, angled to within 2″ to 4″ from the top of the tank. Making the face slope of this rock pile steeper than 450 is not easy. If you think about it, a very tall aquarium with a short front to back “depth” (e.g. a 55 plus at 21″ tall and 13″ deep) is not too practical. Your best dimension ratio of height to depth is as close to 1:1 as possible (e.g. a 120 gallon at 24″ tall and 24″ deep or a 75 gallon at 21″tall and 18″ deep).

Very tall tanks, as well as those with shallow depth dimensions also may pose lighting limitations, with inadequate space for mounting lights, or distances too great from corals to provide them with the light they need. In extreme cases, such as hexagon tanks, one may have problems finding the correct type and amount of lights small enough that will fit on a relatively small tank top.

So in summary, our best tank choice for reef is the classic rectangle shape with adequate depth and not extreme height.

Other considerations:

Please keep in mind that if you choose a reef tank, there will be some trade-offs. You will be limited as to fish type (some will eat corals and other invertebrates) and quantity. Live corals and other invertebrates do best in very clean “nutrient poor” water. This means that they are not very happy in water with a high amount of fish wastes. Less fish equals better water quality which in turn means happier invertebrates. Yes you can have some fish but expect to stock no more than 1/3 of what you might were it a fish only tank. Think of “the reef” as being “the picture” in your tank, and fish are only a part of that picture. If you need for the “main event” to be fish, you may be better off choosing:

The fish only tank

If your desire is a fish only tank (NO live corals or anemones), your choice of fish will only be limited by compatibility and system capacity, but you should keep in mind the time-honored maxim of tank selection: bigger is better.

Especially with a fish tank, the best advice will be to buy the largest tank you budget and space (and possibly your “significant other”) will allow. Large tanks are more stable – that is they are slower to change with respect to water quality, temperature, etc. Saltwater fish need stability. The saltwater fish we keep come from the coral reef which is the most stable, unchanging environment on the planet. Most fish from the reef, therefore, have not developed much ability adapt to change. Change can stress fish, upset their natural defenses against disease.

Large tanks also provide more territory for your fish and are less conducive to “turf wars” among the inhabitants. Remember that all life forms are driven by the need for their species to survive. Chasing away competitors for food and space is merely an expression of this instinct.


Aside from choosing the tank, the next most important consideration is how we will filter the water. It’s very important to understand just what an aquarium filter can (and cannot) do. We generally categorize a filter’s functions into three areas:

Mechanical filtration

This involves the use of some material such as foam or floss to remove visible particles. This makes the aquarium more pleasing in appearance but has little or no bearing on keeping your fish alive.

Chemical filtration

This refers to use of an absorbing material, such as activated carbon or ion exchange resins, to remove the byproducts of fish waste, and other pollutants, from the water. This may have some bearing on fish health, but primarily keeps the water from becoming off color or odiferous with fish waste.

Biological filtration

This is the most important consideration in choosing your filter. Keeping fish in a closed system (like an aquarium) can lead to the problem of ammonia poisoning. Ammonia is a natural chemical excreted by fish and invertebrates, and is also created by the decomposition of most organic matter (e.g. uneaten food). The more fish we put into the aquarium, and the more we feed, the more ammonia is produced. This can be very toxic, even at low levels. The need to “filter” this ammonia before it gets to dangerous levels is crucial. The best “ammonia filter” uses some good bacteria that “eat” ammonia and, ultimately, convert it into a safer chemical. We call this a biological filter.

There are several designs of biological filters, but the best for our saltwater tank is what is commonly called a “Wet/Dry” Filter. In the typical design of this filter, a box (or “sump”) sits beneath the aquarium. In a chamber of this box is a material referred to as “biomedia,” often in the form of spheres or “bioballs.” Over time our good bacteria is grown in the filter (a process we call “cycling”). During operation, water drains from the tank into the filter and over the biomedia. A submersible pump in the sump returns the water back up into the tank.

If the filter is properly designed and sized, the water is caused to constantly re-circulate over the biomedia and ammonia will continually be removed before it becomes a problem.

In choosing a Wet/Dry Filter, there are some very important criteria. The biological, or ammonia-removing, capacity of the filter has two variables:

  1. The Amount of biomedia.
  2. The Frequency, or “turn rate” of water passing over the media.

As a rule of thumb, bioballs or similar media should amount to about a “gallon” of media (~ the amount in a gallon bucket) for every 15 gallons of aquarium water. The “turn rate” should be from 5 to 7 tank volumes per hour. This needs to be measured at the outflow of the return hose back into the tank. Don’t rely on the stated pump flow rate – that is a zero feet of head and your outflow is usually 4 or more feet high.

So this means that a 75 gallon aquarium should have a filter with at least 5 gallons of biomedia and a pump that has an outflow to the tank of at least 375 to 525 gph.

Protein skimmers

These are specialized types of filters that do a great job of separating dissolved organic waste from the water by physically turning the waste into a foam and collecting it as a liquid in a cup. Despite the name, this filter removes more than proteins and can remove waste products that no other filter can. If you have a reef tank, a skimmer is “a must.” Even if you have a fish tank, get one if you can afford it.

There are basically two types of skimmers: one that foams the water with the aid of an air pump and one that forces bubbles into the water via a “venturi” valve feeding into a water pump. Both have merits, depending on your circumstance. Consult your professional store for recommendations.


If yours is a fish only tank, the lighting consideration is basically what is pleasing in appearance to you, so long as you use full spectrum lighting (no “black light” you think will “look cool” – bad for the fishes eyes).

If a reef tank, lighting will be critical, with respect to type and intensity. The options vary depending on your situation and your best advice is from your professional aquarium store.

Temperature control:

The ideal temperature range for most saltwater aquariums is from 75°F to 79°F. That’s a pretty tight range, so we recommend you invest in a good electronic digital thermometer. They cost a few dollars more than the glass tube or stick-on type but are well worth it in terms of accuracy and readability.


Invest in a good quality submersible heater, set it at 75-76° F and check with your digital thermometer. You can leave the heater in your tank year round. It will only come on when needed. NOTE: Be sure you place it in a safe spot where falling rocks won’t crack it or anemones won’t latch on to the surface and get “cooked” when it comes on!


This is a little trickier than heating. Conventional advice has been to purchase a chiller, which is a fancy refrigeration unit made with expensive non corrosive tubing, that can easily set you back ~$1000 depending on your tank size. We almost never sell these devices in our store. We have found that 99% of our customers can control excessive heat via “evaporative cooling.” That’s a fancy way of saying you blow air over your tank water (at surface of the tank or in filter sump) to increase the evaporation rate and therefore increase the cooling. It’s the same principle of early air conditioning (“swamp coolers”), and the way perspiration on your skin on a breezy day makes you feel cool (also think about how blowing on hot soup really does cool it off!). Simple science – and cheap too! The main price to pay is that you’ll add back (fresh) water more often.

How to begin

Now that you have chosen your tank, filter, lighting, and other accessories, your journey can begin.

Once you’ve chosen the perfect spot for your tank (good view, no direct sunlight) hook everything together carefully, according to your fish store recommendations. Take your time and be careful about this.

You may have chosen some substrate (e.g. coral gravel or sand) for the bottom of the tank and at least some of the structure (rocks, deco corals, etc.) that will go into it. Thoroughly rinse the substrate (in a bucket or colander) and set aside until the tank is partly filled.

Once everything is hooked up, it’s time to fill the tank with saltwater. Initially, most folks mix synthetic sea salt and tap water right in the tank. If your water is from a municipal source it probably has chlorine or chloramines in it and a water conditioner should be added to remove these chemicals. Mix the salt on the “low side” at first. In other words, if you have a 50 gallon tank and a bag of salt for 50 gallons, mix only about 80 to 90% of the salt at first. Due to the displacement of rocks, etc. the tank may not hold the stated gallons. Also, we recommend you keep your salinity lower (specific gravity of ~ 1.020) than what most salt mixes achieve.

Mix this salt by hand as well as you can, filling the tank only to about 1/2 at first. Then add your rinsed substrate, rocks, etc. Slowly fill the tank the rest of the way per the instructions you received at the store. When the proper amount of water has been added, turn the pump(s) on and let circulate for at least a couple of hours. NOTE: expect your tank to be quite cloudy for at least 12 to 24 hours. After mixing for a couple hours, test the salinity. It will probably be low and you will add more salt mix, wait and retest until a hydrometer reading of 1.020 is achieved.

At this point let the tank run at least overnight before proceeding to the next step:

Cycling the tank:

The most important first stage in getting your tank ready to keep the creatures of your choosing is to establish your biological filter. By this we mean we must “grow” our nitrifying bacteria in our filter system. We call the process “Cycling.”

If you are using the wet/dry filter, we want to grow these bacteria on the surface of our bioballs to a maximum possible amount. Remember, it is these bacteria which will protect our fish by removing toxic ammonia and nitrite. You may hear of possible ways to establish these bacteria, some involving the use of bottled bacteria, or “starter” substrate from an established tank. In our experience these are imprecise methods which make difficult one’s determination that “resident” bacteria are well established and growing on the filter.

We prefer to start a saltwater aquarium using fish, preferably damsels. We like damsels as they are hardy and inexpensive saltwater fish and they can generate a lot of ammonia, which is food for the bacteria. The process goes like this:

  1. Add damsels at the rate of about one per five gallons tank capacity. From the gut and skin of these fish is introduced a small “seed” of our bacteria.
  2. Feed generously 2 to 3 times per day. It’s OK if there is uneaten food – this creates even more ammonia for the bacteria.
  3. Test a water sample at 7 days from step one. We should see the ammonia amount “off scale” on our test chart. NOTE: with this toxicity we may loose some damsels – on average 1/2 may not survive the cycle process. It’s OK to leave dead ones in the tank (creates even more ammonia).
  4. If ammonia is very high at 7 days, we can then cut the food back to once a day. If not we may do well to overfeed for another week.
  5. As we test again (~weekly) we should see the ammonia come down to zero in a week or two. This tells us we had to have grown lots of our first bacteria (“nitrosomonas”) to get rid of this large amount. This is how we know we are having a good cycle.
  6. In the next phase, our “nitrosomonas” bacteria will have converted the ammonia to another toxic chemical – nitrite. The Nitrite, likewise, should go off scale until a sufficient amount of our second bacteria (“nitrobacter”) grows and converts the nitrite to nitrate. This stage happens more slowly that the first stage.
  7. Therefore, after we have seen an off scale ammonia, followed by an off scale nitrite, and then both levels back to zero, we can consider the tank “cycled.” NOTE: this process usually takes at least 4 to 6 weeks (as determined by tests).

During the cycle we are loading a lot of waste products into the tank and it will usually not be a pretty site lots of algae growth, as well as possibly off-color or off-odor water. In any event, it’s probably a good idea to do one’s first water change at this point in time – prior to adding fish. This should be about a 25% change using a gravel vacuum to remove solid wastes. Your aquarium store professional can help you choose one. At this time you should also consider using saltwater that has been prepared using reverse osmosis water. This water has had any undesirable impurities removed from the tap source. A good aquarium store should offer this type of prepared water.

Adding fish and invertebrates

Prior to embarking on this venture you should have made at least a general plan as to what you’ll keep in this aquarium. If not before, then during the 4 to 6 week cycle you should be making a list of specifically what life forms you think you’ll eventually want to own. Our section on Fish Suitability may prove helpful. Go over this list with your aquarium store professional and distill it down to a realistic and workable plan. It is very important to make additions to the aquarium very slowly with reasonable time intervals between additions. Start with the hardiest and less expensive things first. Always learn the basic needs and personalities before purchasing.

Aquariums and aquarium owners get better with time. The single biggest mistake you can make is to get impatient and proceed ahead of your “learning curve.”


Ask questions. Read. Learn. Enjoy!