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Basic Components of the Marine Tank--Introductory Article
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PostPosted: 2003.02.18(Tue)20:25    Post subject: Basic Components of the Marine Tank--Introductory Article Reply with quote

The following is an article that focuses on the topics of water quality, equipment, live rock/live sand, and initial establishment of the marine aquarium. If you are unfamiliar with basic concepts of fish-only and reef tanks (and what can inhabit each compatibly), please read this first.


Water: The Vital Ingredient
A basic understanding of water chemistry is extremely important in properly maintaining a saltwater tank. This is why people who have never kept any type of fish before may be better off starting with a simpler freshwater tank first before tackling marine, just to acquire very basic experience, such as with the nitrogen cycle (explained here). Marine animals are more sensitive than freshwater fish to dissolved solutes and impurities, such as those usually found in tap water. Freshwater animals may not be affected by anything except chlorines and chloramarines in tap water (removed by dechlorinator and stress coat type products). For marine animals, even tiny ppm (parts per million) fractions of impurities may be harmful--think of the natural coral reef, and how pollution-free this environment is. The only way to really get rid of these is through water purification. For small tanks (10 gallon size), you can get by with use of something like a Brita filter, a "water purifier column" (a modified ion exchange type of low-tech system which binds impurities, fairly slow and cumbersome to operate, and does not yield much volume before it must be replaced), or even just buying distilled water in bottles at the supermarket. These methods, however, aren't efficient for larger volumes, and can be a pain over the long run given that regular water changes are a necessity. The best investment for the future is in an RO/DI (reverse osmosis/deionization) system. This runs automatically off of tap water pressure, and uses this pressure to force water through a series of membranes and filters that take out everything except the H2O.

A water purifier column (Aquarium Pharamceuticals) shown on the left, and an RO/DI system with storage bin shown on the right.

This water should then be made up to saltwater in a separate bin with commercially available marine salts such as "Instant Ocean" and "Tropic Marin" (there are very slight differences in ratios of trace elements in each brand name which are beyond the scope of this article, but which are compared here; the important thing is just to use a salt meant for marine tanks, not "aquarium salt" which is just pure NaCl, used for treating FW fish). Specific gravity (S.G.) measures salinity, or actual concentration of the salt... for marine animals, this should fall in the 1.023-1.025 range. S.G. should be measured with a hydrometer. Other tests which are absolutely vital for beginners to own include ammonia and nitrite (both should be 0 at all times in a cycled tank) and pH (should be roughly 8.3-8.4). pH can be kept stable through addition of a marine buffer (never ever try to adjust pH through addition of bases alone!), and in water changes or anytime there is life in the tank, this should all be done in a separate bin and premixed with the salt. Other good tests to have that are not as vital include KH (to measure buffering capacity, which determines pH), nitrate and phosphate (both best kept at a minimum for optimal coral calcification, and to prevent pest algaes from blooming), calcium (best kept as close to or above 400 as possible), and copper (absolutely needs to be kept at 0 in all reef tanks; it is an ingredient in antiparasitic fish meds and sometimes seen as a trace in tap water, but is highly toxic to all inverts). Some more fastidious corals may require dosing of certain trace elements (come in commercially available formulas to add calcium, iodine, strontium, etc.) and some filter-feeding organisms may need separate feeding with phytoplankton. There are also more automated accessory pieces of equipment for these purposes (I.e. the Nurce, the calcium reactor, etc.), but they will not be covered here.

I want to make special note at this point that I have to talk in generalities for marine animals here, but there is actually a great spectrum of tolerance and preference between all the species you could potentially keep. Some beginners may be able to get by without any kind of RO/DI or purification system, if they live in a geographical area where the water supply is not very treated, and/or they are keeping fish that are not sensitive to trace impurities (some damsels and triggerfish are just about as hardy as any FW fish in this respect). The degree of precaution you take with your water depends in large part on what kind of tank you want to keep and where you are located (to be sure, call your water company for a consumer report of what goes into your water, or contact an experienced hobbyist, reefing club or marine LFS in your region). Also, you won't have to worry about trace element supplementation in the majority of FO or FOWLR tanks.


Filtration and Protein Skimmers
Filtration can get very complex for marine tanks, and does depend on what types of animals you keep and at what density. In FO (fish-only) tanks, a number of the same filter types as those familiar from FW systems are available, including canister filters, hang-on-the-back style power filters, etc. (see the second article on filters for more details). In addition, there is a very efficient type of filter called the wet-dry trickle filter which is often employed for the marine FO tank. This basically operates on the principle that the bacteria involved in the initial steps of the nitrogen cycle are primarily aerobic, and so love well-oxygenated water. The water is taken out through an overflow box in the back of the tank, down through the plumbing, into a sump (a tank that sits under the main aquarium), and through a series of baffles and holes that lets the water trickle over media with a lot of surface area (where the bacteria live). It is then pumped back up into the main tank with a separate external water pump.

An example of a sump wet-dry trickle filter, with overflow box shown on the right

While these work for well for FO tanks, I should mention that the trend in reef tanks is away from mechanical filtration and "classic" types of filtration altogether. They are able to do this because reef tanks usually have very few fish and very low bioload, so they do not produce much waste at all (but conversely, do not tolerate any levels of ammonia or nitrite, and in addition, are sensitive to nitrate and other trace readings). "Classic" filtration, while good for sieving out solid particles and quickly converting ammonia and nitrite, also can build up nitrate, which is relatively harmless in FO tanks at low concentration. However, even low levels of nutrients and dissolved organic compounds (DOC's) can be suboptimal for corals, so the trend in reef tanks is towards greater use of live rock/live sand (both discussed below) and other "natural" filtration systems, such as the refugium (A refugium is a body of water physically separated from the main tank, but which shares a common circulation and water supply, for the purpose of growing beneficial animals and plants).

This beautiful HOB style refugium (created by CPR, brand name "Aquafuge") is not only functional but can be a beautiful focus of attention all its own. They are places to foster the growth of caulerpa (a macroalgae which takes out excess nutrients like nitrates and phosphates, decreasing algae in the main tank) and protect the growth of smaller dentrivores (various species of microfauna, mostly pods, which help decompose waste), which suffer excess predation in the main tank.

The last element generally included with filtration (but technically slightly different) is protein skimming. This is highly recommended for any marine tank with fish in it, especially one that is well-stocked. There are small technical differences between the various types of skimmers, but all work on the principle that organic waste (primarily fatty and proteinaceous in quality) tend to float to the top of the water column; the protein skimmer uses the foaming up of tiny bubbles in a special chamber to separate them from the main flow of water. They are often combined with sump wet-dry filters or other types of filtration (in a smaller HOB filter, the combined name is "skilter").

A typical Berlin style protein skimmer


Though not an absolute requirement in some fish-only tanks, extra powerheads (which are just little mini-pumps for moving water around) can add overall benefit. They not only stimulate circulation and prevent dead zones in the tank, they also create flow patterns in the water that simulate natural waves. Different corals like current to varying degrees (individual preferences require some personal experimentation). Some people put their powerheads on "wavemakers", which turn different ones on and off in a regular pattern, further creating wave effects.


Live Sand: Laying Down the Foundation
Sand for the marine tank is more than just substrate. In an established tank, it will become home to millions of bacteria that help with the nitrogen cycle, as well as dentrivores (tiny animals that help consume and decompose waste and uneaten food; in particular, amphipods and copepods). For the marine tank, the composition of sand that works best is calcium carbonate (AKA "aragonite"). This can be found in crushed corals (CC), or finer sands. For most purposes, the finer and rounder sands work better for promoting dentrivores than CC, which can have jagged edges and is of a large gauge, but both are OK. Silica- and quartz-based sands are fairly inert and also alright to use, but will not give the same buffering benefits of aragonite. Brand names of commercially-available aragonite sand that are safe to use include "Southdown" and "Yardright" Caribbean play sands (from Home Depot and Lowes hardware stores, respectively, only in the NE United States, far more difficult to find in other parts of the country), and for those who have to resort to buying more expensive LFS brand names, "Caribbsea" and "Aragamax". For the best results, sand should be laid down in the very beginning, because it will cause white cloudiness for days (this is not harmful to life, but it can be a pain to watch and wait out). For optimal effects, a deep sand bed (DSB) should be relatively deep; at least 4-6" in small to medium sized tanks, >6" in large tanks (the deeper, the more benefits to the denitrification process). You do not need to buy it all "live" to begin with and should buy it dry in bags (rinsing is not necessary, as there are beneficial sediments in the sand, but expect lots of cloudiness either way for a long time!). Large quantities of truly "live" sand are very expensive and difficult to obtain. Most people layer their dry sand, get their systems up and running, and then "seed" it from another source; a generous fellow reefkeeper who lives in the area, an LFS with a healthy display reef tank, or if they can afford it, buy it online from a place such as Inland Aquatics. Most of the bugs in the sand will reproduce and spread fairly fast under good conditions. You will know it is truly live when you see small tunnels digging through your DSB, usually the work of little shrimp-like crustaceans called amphipods.

An amphipod is a small beneficial creature you may find crawling through your live sand once the tank is established.


Live Rock: The Cornerstones of a Healthy Tank
Many new to the marine hobby gasp when they hear prices, but especially when they hear the prices for live rock. It is probably one of the more expensive items that can be bought "per pound" from a pet store. However, it is for a reason that this stuff is not cheap. Live rock is the actual foundation of the reef itself, intricate calcium carbonate skeletons that were once put down by countless corals over the ages. It now comes at a high premium due to laws that ban or limit collection in most areas of the world (for good reason, since the uncontrolled collection of it has the potential to dessimate the endangered reef). However, when you buy the good stuff, you are buying much more than just "rock" for decoration. You are buying a storehouse of beneficial bacteria that will function as natural filtration to clear your water of impurities. You are buying protection and homes for the fish and inverts on your list later, and anchoring places for coral. You are buying a huge number of beneficial hitchhikers that you don't see right away, which will reproduce and help establish your tank... most importantly, a number of dentrivores, such as amphipods and copepods. Not only this, but because it is made up of calcium carbonate, it will also help buffer your water as it adds dimension to the physical appearence of the tank. So the more the better... but not only quantity (per pound), but you should look for quality in live rock:

1) Try to go for Fiji rock when you have a choice. This is less dense and more porous.
2) While the large majority of hitchhikers (bristleworms, various pod crustaceans, spaghetti worms, feather dusters, etc.) are good, try to avoid anything which may have mantis shrimp or aiptasia (a pest anemone that reproduces very fast) in it. Hitchhiker ID is beyond the scope of this article, but some good FAQs can be found on the subject in Reef Central's library.
3) Truly "live" rock should be stored in a tank with active circulation and heated water. If it is dry, then this can be used as base rock (to build a foundation), and true live rock can be laid over it; this can be money-saving, and eventually the live pieces will populate the base rock.
4) Coraline algae (encrusting, hard purple calcified algae) and bryopsis (a brush-like, dark green macroalgae) are types most people find attractive and desirable, but other types of algaes may become a pest.
5) Look for interesting shapes and holes, where fish and inverts can create homes; this also helps when aquascaping with corals.

A small piece of quality live rock, such as this coraline-covered Fiji piece) may hide a whole living universe.


Let There Be Light
Lighting, as mentioned previously, is not very important in the FO or FOWLR setup, but is the most important, and usually most expensive, piece of equipment for the reef tank. It's for good reason--the large majority of corals and anemones depend on good lighting for photosynthesis. To understand lighting, we have to understand both the elements of color spectrum (quality of light) and intensity (quantity of light). Most normal output fluorescent lights that come standard with many hoods are fine for fish and look OK to the human eye, but inadequate for growth of almost all corals and anemones, in both spectrum and intensity.

Color spectrum refers to the wavelength and frequency of the light (which are in turn inversely proportional)... to the human eye, they appear as different colors, with red on one end and blue-violet on the other end of the visible spectrum. Most photosynthetic pigments that are needed by the zooanthellic algae living within corals require a wide spectrum, with peaks in the red and blue range. Blue light also has the added advantage of being able to penetrate water to greater depths, since it has shorter wavelength and greater frequency, which is why many "actinic" lights (very blue in color) are used in reef tanks. Color is measured by the Kelvin (K) rating.

Light intensity is measured in lumens. Output and intensity does decrease with time, so bulbs must be changed regularly (interval and half life depends on the specific type of lighting used). It is primarily achieved through 3 types of alternative high output lights, which also each require their own special ballasts:

Power Compact Fluorescent (PC)
Very High Output Fluorescent (VHO)
Metal Halide (MH)

One style of PC lighting

There are pros and cons and individual opinions on each one of these light types that are simply beyond the scope of this very basic article, since this is another complex and controversial topic. Also, not all corals and photosynthetic organisms do best under the same exact lighting requirements (as a general rule, most "easy care" soft corals are OK with low to moderate lighting, but SPS and clams require high lighting). I will defer a more detailed discussion of this topic to this reefkeeping 101 article on lighting or Albert Thiel's Chapter on Lighting, in THE MARINE FISH AND INVERT REEF AQUARIUM.


So, there you have it; a relative crash course in saltwater basics. Now that you have all this equipment, what next?

The growth of microfauna (tiny animals & bacteria) in live sand and live rock can be promoted by the process of cycling the tank before you add any of your fish or main invertebrates to the tank. In some ways, cycling a SW tank can be easier than FW because of these "live" elements (sand & rock) and the decreased emphasis on external filtration. One method is to throw a frozen shrimp into the tank once it is set up and running with all the above elements, and just let it decompose for a at least a few weeks (this is before you add any of your livestock to the tank). Do regular measurements of ammonia, nitrite and nitrate; initially you will see the first two spike up due to the shrimp addition. As it decomposes, you should after a few weeks see them go down to zero and your nitrates rise; when both ammonia and nitrite are steady at zero, you are done cycling, and ready for your fish and/or inverts, and eventually, your corals! Yes, this takes a long time, but rushing to add animals to an uncycled tank can spell disaster in the early stages of tank setup.

I was told something years ago that really stuck with me: "In this hobby, only bad things happen overnight. Good things take time." Along those lines, I guess one could say that the most important basic components of a marine tank are patience and knowledge. Since the day I started with this hobby, I haven't gone a day without learning something new about it, and I hope you don't either. Have a good time with it, and please check the other marine & reef links for more information sources and places to do further reading!
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