This used to be for the big boys only but it's getting a lot easier.
It can be a technophiles wildest dream come true or a technophobes nightmare but if you're patient, get to grips with some basic filtration and water maintenance it can be so amazing.
Marine fish and animals ARE more sensitive to water conditions than their freshwater cousins. Here, in simple terms is why.
In a freshwater habitat things change. If your river or pool dries up, chemicals become more concentrated. When it rains or floods again, they dilute. If you are in a pond and a dead animal falls in, the water becomes at least slightly polluted and you can't escape.
You adapt or die.
In the sea (there really is only one) rain has no effect at all on the chemical composition. If a dead cow drops in, although it may cause a localised problem for a short time, either you can swim away or tides and currents will carry out massive water changes in short order.
Life is stable.
It is maintaining this stability that is critical in keeping marine tanks.
Tanks for marine aquaria should ideally be a minimum of 50 gals. This improves the stability of the water conditions and allows a number of fish etc. to be kept. Marine stocking levels are far lower than freshwater and small tanks simply don't hold enough fish! There are different types of marine set-ups, detailed below, but all rely on good filtration and Protein Skimming. Protein skimmers work by mixing fine air bubbles with water. The bubble's surface attracts and holds protein and other organic wastes. These form a scum that rises to the surface where it overflows into a collection cup for disposal. Always get the biggest and best skimmer you can!
These tanks can be run with efficient, powerhead operated under gravel filters. The normal set up is to use two layers over the under gravel plate. The first is about 2" of crushed shell. This is topped by a gravel tidy, a plastic mesh, to stop the two layers mixing ( and to stop fish digging ) topped off by another 2" of coral sand. Alternatively ( preferably in my opinion ) use a large external power filter filled with biological media and floss. In this case the tank can either have a bare base or an inch or so of coral sand. Regular maintenance is essential. This consists of regularly monitoring the water quality and changing 25% of the water fortnightly. Don't forget this when you are setting up as you will need facilities to make up this replacement water in a separate container before every change.
In a marine set-up you want to avoid changing things and this means avoiding changing water. The nitrates that conventional filters leave behind can be dealt with by a) water changes, b) heavily planting your tank or c) in marine aquaria using the Berlin Method. This system uses a protein skimmer, a mechanical filter, lots of water movement and 'live' rock.
The mechanical filter is just that. Its job is to get rid of solid wastes from the tank. A powerful external filter does the job well and has the added bonus of producing lots of water movement. Something that turns over the tank volume two to three times an hour should do the trick. This filter must be kept purely mechanical i.e. the media should be replaced or cleaned in tap water to kill any bacteria at least once a week. This is essential to keep the nitrogen cycle (biological filtration) in balance.
The biological filter takes the form of live rock. This porous rock comes complete with a population of bacteria, sponges and tube worms all of which help to clean and filter the water. The bacteria in particular form a balanced community of bugs that will convert ammonia to nitrite, nitrite to nitrate AND, in the oxygen starved interior of the rock further bacteria convert the nitrates to oxygen and free nitrogen gas. It is because this is a balanced community relying on the percolation of water through porous rock that we must restrict the amount of biological activity produced elsewhere. If your mechanical filter becomes 'live' it will produce extra nitrate which the rock will not be able to cope with. The tank water obviously needs to be in contact with the rock and this is the reason you need lots of water movement, from your power filter but also some additional pumps or powerheads. swhglop[?@ jrwoi5t9q3jreoigjsdfgj (sorry, that last bit was typed by Katy. )
This system has a lower stocking level for fish than a fish only system but you can keep corals and other invertebrates in this kind of tank. Fish obviously need to be 'reef friendly' so large angel fish and Triggers, which eat corals and live rock are a no-no.
Lighting is important. It needs to be reasonable but not very intense unless you want to keep light sensitive invertebrates like some anemones and corals. About 30-40 watts of florescent light/ sq.ft. will normally suffice. This should consist of a mixture of bright white and actinic blue lamps. Alternatively metal halide lighting suspended over an open tank provides intense sunlight effects. Intense lighting will enable you to keep hard as well as soft corals.
You can get away with fewer water changes ( 20%/month ) but you will need to top up evaporated water using pure water. You will also need to add supplements and trace elements like Strontium and Molybdenum, Calcium and Iodine on a regular basis as they are used up by the coraline algae and corals.
This is a further development of the balanced Berlin System. The tank is set up with a live plenum in the base. This works as a very efficient biological filter and has additional benefits in stabilising water conditions. The plenum consists of a 1" 'void', a 2" layer of aragonite sand and a further 2" of 'live' sand. The void is created by sticking 1" lengths of pipe to the aquarium base. This is then topped off with a tight fitting acrylic egg-crate (similar to that used in florescent lighting ) and a gravel tidy, sealed round the edges to prevent any media spilling into the void. The 2" of sand is place on top and again sealed in place with a gravel tidy. The system is finished off with 2" of live sand. This is home to the usual filter bacteria but will also house crabs, worms, invertebrates and small fish that turn over the sand, keeping it fresh and preventing it from compacting. Live sand can be very expensive. If you have the patience you can use plain aragonite and add just one pack of live sand which will then seed the rest. This system is very efficient ( if you get it right ) and has been successfully employed in some of the best public aquaria, e.g. the Monaco Aquarium. Corals, live rock and other decor can be supported on glass shelves to avoid compressing the sand bed.
With metal halide or very intense florescent lighting this system will maintain live hard as well as soft corals.
Yes, mud. The latest eco-system for filtering marine tanks is to use a separate tank under or connected to the main tank. In here there is a mechanical filter which removes large particulate waste. The clean water is then passed over a live mud bed. Growing in this is Caulpera seaweed. The combination removes and processes the waste materials from the water. This is then passed through another mechanical filter (to stop fronds of caulpera) before being pumped back to the main tank. Heaters can also be included in this tank, removing them from the main display. Proponents of the system claim that it is so efficient at waste removal there is no need for protein skimming. The filter tank has 24hr. lighting to encourage the growth of the macro-algae which is harvested regularly to remove the processed wastes from the system. The sump also allows the growth of many micro organisms, like plankton and small invertebrates which are returned to the main tank as fresh, live food.
The add-ons available to the marine aquarist are un-ending. I'll start simple.
Wave makers. These control two or more pumps or powerheads to provide a changing water flow to simulate the back and forth wave action found on natural reefs. They can go on to include systems with reservoir tanks where water is removed from and returned to the main tank to simulate high and low tides.
Lighting controllers. Sometimes no more than simple timers to give dawn and dusk effects by switching actinic blue lamps on an hour or so before the white lights and off an hour or so after. They can extend to systems controlling banks of lights to give simulated lunar cycles.
Dosers. These may be no more than a gravity run drip system adding water to the tank to replace evaporate. The replacement water may also contain trace elements like calcium and iodine. Larger systems may include a larger reservoir tank and a pump controlled by a float switch in the main tank to maintain levels.
Calcium reactors. These are very popular add-ons for reef tanks. Carbon dioxide is mixed with tank water to create an acid condition. This is then pumped through a column of aragonite or other calciferous material to increase the free calcium in the water. pH controllers can be used to regulate the activity of these systems.
Coolers. Reef tanks suffer if the temperature rises in hot weather. With all the electrics (pumps, lights etc.) tanks can overheat so coolers keep the temperature in bounds. Coolers, unlike heaters, are expensive but so are reef tanks and the livestock in them.
UV and Ozone are both used as sterilizers in marine tanks. Ultra violet lamps are used within a water jacket to destroy any bacteria or parasites free swimming in the water. They need a pump to pass the water through the tube but can also be fitted on the output side of a filter. Clean water allows the UV to penetrate the water effectively. Ozone (O3) is a three atom molecule of oxygen. Ozone is fairly unstable and the extra atom will attack proteins it comes into contact with. An electric arc is used to create ozone from a dry air supply. This can then be used in a protein skimmer to help get rid of excess protein in the water. Ozone can be troublesome. Even a low level in the air we breathe can cause headaches. The escaping air from the skimmer either needs to be vented outside or passed through active carbon to return it to the more stable O2 we normally breathe.
There are also computers available which will control all or most of the above.