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Dream tanks… we've all wondered what it would be like to have a giant aquarium. Most of us are still wondering! Yet saltwater displays above 200 gallons have become familiar fixtures in the trade. The evolved state of the hobby, as well as the improved availability of hardware and livestock, have made the "dream" more possible and affordable than ever before for aquarists. A visit to most any suburb near a big city and you will inevitably find an aquarist at home with a saltwater aquarium big enough to bath in.
Super-sized aquariums are no longer reserved for the experts either. Reliable and turnkey plumbing and filtration kits are available for the mechanically disinclined, and a plethora of DIY data and support abounds on the Internet for the handy aquarist. Commercially propagated and even locally grown animals have made stocking big aquaria easier and less expensive, particularly among live coral traders. Indeed, this primer not only addresses big fish in a big aquarium, but big populations of smaller fishes and invertebrates as with reef type aquaria.
Some of the basic elements that should come to mind for big systems include: Filtration, Lighting, D?or, and Husbandry. Providing adequate biological filtration is surely the most daunting of the aforementioned. Aquarists familiar with pond-keeping and aquatic gardening are at a decided advantage here. The cultivation of nitrifying faculties for a large marine bioload is fundamentally not unlike keeping koi and other pond species. One could even make the argument that it is slightly easier with marines in part for the nature of foods fed (more dense and efficiently utilized by tropicals) and support from complex natural dynamics like denitrification in live rock and deep sand beds. Other similarities can be fairly observed. Bog filters (the inline, shallow water regions planted heavily for nutrient export) have been readily embraced by pond-keepers for their efficiency and natural beauty as living filters. Marine aquarists have found planted refugiums to be invaluable vegetable filters just the same. Both methodologies require harvest (pruning or thinning) to export nutrients while maintaining health and vigor of the vegetable mass. Refugiums are strongly recommended for large aquaria to accomplish some or all of the following as well: mediation of water quality, stabilization of pH (reverse photoperiod systems), plankton production, and as a settling chamber.
The overall approach to plumbing and operating a large system is simply a matter of scale when compared to a smaller home aquarium. You will find, however, that many obligations to water quality are much more strict with a heavy bio-load. Testing for less common parameters like oxygen saturation and phosphate levels may be easily overlooked (and certainly more easily corrected) in a smaller system, but a large aquarium requires due diligence, patience and planning to control these and other parameters. They are subject to the virtues and limitations of their very size. Both good and bad things are likely to happen slower in a large volume of water. We gain greater stability with increasing tank size. Thus, climbing nitrate levels are easily observed in advance, but a dangerously low level of oxygen cannot be remedied quickly, for example. This reality demands that you pay strict attention to simple but thorough articles of aquarium husbandry.
With careful feeding, light stocking, regular water changes, etc., you will be able to enjoy a remarkably easy system at any size. Set realistic goals for the bio-load and have a planned stocklist in advance (including a proposed order of introduction). A super-sized aquarium does not mean "unlimited" potential stocking with fishes… it just means you may have to scrape algae with a mask and snorkel. There is a finite and practical stocking density to any aquarium. Rules of thumb such as X inches/cm of fish per gallon are really inappropriate without perspective. Beyond the obvious differences and potentials to various filtration methodologies when placed on the same sized aquarium, there is the very real matter of mass versus length. Ten dainty cardinalfish at 3 cm (1.2 inch) each do not place the same demands on filtration as one 30 cm (1 foot) sloppy grouper… yet they are the same cumulative length of fish! Thus, you can quickly see how flexible we must be on guidelines for stocking densities in a given aquarium.
After considerations for the space needed for your creatures at adult size has been addressed, the focus on filtration must turn to efficiency and reliability. In the scope of this article, an overview of the most popular modes is offered. More specific if not scientific detail is given to such dynamics and beyond in the fantastic book by Escobal, "Aquatic Systems Engineering." It is a technical but reliable reference that simply must be on the bookshelf of serious aquarists and operators of large marine aquaria.
Trickle-filters are one of the very best types of filtration for heavy bio-loads. There are numerous interpretations of the concept for large and small aquaria, indoor and outdoor applications alike. They offer an ideal combination of significant surface area for nitrifying biological faculties while exploiting the unlimited availability of oxygen (in atmospheric air) in the moist environment of the media chamber. Since the media is not submerged in system water, it does not compete directly with livestock for oxygen in the event of a power or equipment failure (trickle filters can generally endure longer and stronger during such catastrophes). This style of filtration is recommended for moderate to heavy bio-loads.
Fluidized bed filters are also highly touted. They operate by churning a suspension of sand or plastic beads in a flow of raw water. The extraordinary surface of the fine media foster even greater surface biological activity than trickle filter media per pound. As such, they can be made smaller to handle the same bio-load, and are indeed space saving. As submerged media, however, they are wholly dependant on the flow of water to bring food and oxygen to them. In some ways, they compete with livestock (for oxygen) and can contribute deleteriously to water quality if overfed (fast nitrate accumulation). In the event of a power or system failure, this submerged media is vulnerable as it settles and suffocates its tremendous colony of aerobic bacteria. At length, fluidized bed filters are superb for very heavy bio-loads and situations with limited space for life-support equipment. Any concerns about its limitations are easily remedied with back up generators, pumps and alarms that are well worth the investment for dream aquaria.
For resourceful aquarists, there are excellent pond and DIY designs for large aquatic filtration systems that can be constructed with inexpensive materials like plastic barrels (food safe), feed troughs, garbage cans, and more. Explore garden pond outlets, books and other sources for products and concepts that can be adapted for large aquaria.
Protein skimmers are also highly recommended for big marine systems. In fact, they are so efficient at nutrient export that water quality will benefit immeasurably with two skimmers in operation. The suggestion is to keep two unique styles (venturi, airstone, injection, or aspirated) because different skimmer designs can extract different qualities of skimmate. Alternate or stagger cleaning and servicing events to ensure minimally interrupted skimmate production. While large water changes and chemical filtrant exchanges can be cumbersome, impractical or expensive on big systems, protein skimmers can temper the degradation of water quality inexpensively and effectively. Protein skimmers are also a crucial means of supporting oxygen saturation in a system with a heavy bio-load.
A brief but important mention of aquarium tank and stand fabrication is in order. A few hundred gallons of water translates to a few thousand pounds of weight. For the safety of your person and property, be sure to have a professional evaluate and confirm the integrity of the aquarium and the solid foundation of the stand, as well as the floor upon which it sits. Most large aquariums over a few hundred pounds will need to be set on solid ground (concrete flooring). When this is not possible, strategy will be required with an orientation perpendicular to the run of the floor joists and possibly with the support of floor jacks underneath. The stand upon which the tank sits is to be as close to perfectly level (planar) as possible with a tolerance of mere fractions of an inch (a few mm). Imbalanced tanks can place undue pressure on a side or seam and cause a leak. Irregular surfaces (knots, divots, fastener heads poking up, etc.) can cause pressure points and lead to a crack in the glass or acrylic. Likewise, the posts and pillars of the stand should make a large footprint to distribute the weight of the aquarium. Narrow legs or excessive shims can cause dangerous pressure points, which will lead to a twist or torque of the aquarium. Such flaws are often called to pay the price if the foundation (solid or otherwise) settles even slightly in time. One way to compensate for small flaws is to bed the aquarium on a thick slab of non-absorptive (styro-)foam. Without padding, it is crucial to ensure that the stand top is not porous at all but rather very dense. Particleboard and pressed wood are terrible materials for stand construction and will absorb water, swell and can cause a leak in the tank (the uneven stress pulls a seam). Very solid materials are necessary for aquarium stand construction overall.
Lighting any tank is a matter of depth and delivery. The transmission of light is reduced at increasing depth. The luminary needs of the inhabitants will dictate the hardware necessary to meet the demand. For photosynthetic plants, algae and animals in water deeper than 24"/60cm, metal halides may be required. For large marine aquaria that are long but shallow, modern efficient fluorescent lighting will work very fine like T 5 technology. Whichever lighting you choose, be sure to employ efficient reflectors (like parabolics) to optimize the distribution of light into the aquarium. Most importantly, choose your livestock and identify their needs before buying a fixture. Too many aquarists buy lighting to fit a tank size without consideration of the living guests.
Options for d?or in large aquaria are limited only by one's imagination. A wide variety of natural and synthetic materials can be used to construct attractive and effective habitats for the aquarium residents. Natural substrates like rock, gravel and sand are handsome but heavy. Artificial substrates like plastic, fiberglass and resins are lightweight but inefficient in many ways for a lack of porosity (limiting their ability to become significantly biological in time). Enlisting the minds and resources of a good aquarium society can be quite helpful for perspective from experienced and well-traveled aquarists. Some public aquaria personnel are also kind enough and able to chat with private aquarists about large system features and artifacts. A behind the scenes tour of the exhibits is well worth a pint of beer or two for a friendly staff member! Be resourceful… and be imaginative.
If compatible with the species and habitat you seek to replicate, a healthy portion of live rock will serve incomparably as d?or, food (generating plants, algae and plankton), and as bio-filtration. Aquacultured live rock and wild-harvested product are available and each has their own merits and limitations. To facilitate a better price and perhaps product quality or shapes, it will be helpful to seek a local aquarium store that can piggyback your order with one of their normal shipments to optimize freight and the cost of importation. Many local merchants are quite accommodating in such matters and in doing so earn a fair commission, negotiate a better price from a distributor for you, and finesse good will for all in the process. Use live rock and live sand wherever possible in natural marine aquariums large and small.