The aquarist nowadays has quite a choice of support equipment available. All this aquarium equipment, along with routine seawater changes, makes keeping high quality seawater easier. This is very important for the livestock be they fish or corals or whatever.
‘High quality seawater’ means something a little different to each aquarist. One aquarist may keep a fish only system, another a soft coral reef, and another a hard coral (SPS) system. The quality depends on what is being demanded.
Basic high quality is seawater without any toxins (ammonia and nitrite), at the correct pH, at the correct temperature and with a low nitrate presence. The quality is generally stable.
Basic seawater could be found in a fish only system. Nitrate is the usual problem with these, if there is a problem.
In the soft coral reef, in addition to the ‘basic’ quality, will be the alkalinity level and possibly also the calcium presence. Alkalinity resists changes in pH, and also appears to assist in the appearance of encrusting decorative algae. There is also a low demand for calcium, which could be met by the dry salt mix or, if not, by an additive.
The hard SPS (small polyp stony) coral reef has the same requirements as the soft coral one but again with additions. The aquarist will keep a closer watch on calcium and perhaps one or two others. SPS corals have a higher demand for calcium and, depending on stocking, it probably will not be met by the dry salt mix so an additive is required. In the larger aquarium, a calcium reactor could be used.
The above paragraphs are not meant to be a list of different system requirements, only to give a start to the support equipment needed and the choice of ‘the most important’. Of course it can be argued that all are important for the needs of different systems. How about an auto top-up system for example, particularly on larger aquariums? Keeping the level correct reduces salinity instability. In the same way there are calcium reactors, exterior heater controllers, kalkwasser stirrers, lighting timers, powerheads for seawater movement, return pumps for use in a sump etc.
Specific equipment is important to a particular system, and perhaps useful but less important to another. So is there a general piece of equipment that could be of use, or better put, is of use to all systems?
What is it that often rears its unwanted head and can cause trouble for the aquarist? Unsightly algae could appear which, if present in quantity, may drive the aquarist to near despair and spoil an otherwise lovely display. More sensitive corals and even fish are affected by too high a presence. It could appear in any type system, fish only, soft or SPS reef.
Nitrate is the answer. In a reef system the guideline is 10 ppm (parts per million) or less – in a fish only preferably the same, but at least as low as possible. Nitrate is controlled by proper stocking (particularly fish), careful feeding and routine partial seawater changes. Nevertheless, nitrate is often in excess.
Nitrate is a product of the nitrogen cycle which occurs in the bio-filter. Bacteria convert toxins and eventually the resulting nitrate (if live rock is in use in sufficient quantity and quality) is broken down and released from the seawater as a gas. Yet nitrate could get to excess levels despite this. Where the bio-filter is contained in a canister filter the nitrate is the end product and without care will continue to rise.
This is our clue – what piece of equipment can be of use in all systems and combat nitrate? The answer of course is the protein skimmer. This piece of well known equipment is benevolent to all system types (except specific ‘mud’ though many aquarists use a protein skimmer anyway).
Generally seawater moves through the skimmer steadily and dissolved organic matter (DOM) is removed. This improves the seawater straightaway as excessive DOM is not required. (It is known that corals, or at least some of them, can make use of DOM as a food source, but DOM should not be in excess.)
What is really good is that the DOM is removed entirely from the seawater and stored. Not being in the seawater the bacteria in the bio-filter cannot act on it, in other words it is no longer a source for nitrate. The protein skimmer is not the total answer for nitrate but is very helpful.
Even without that aspect, just look at the yukky brown smelly gunk that could appear in the collection cup. It must be better with that out of the seawater!
So, disregarding equipment that is essential to life itself such as heaters, my choice for the number one piece of general marine system support equipment is the protein skimmer.