Most fish that I am about to discuss are going to require an aquarium with the minimum dimensions 6'x2'x2'. Although a larger 8'x2'x2' would be far preferable and ideal for big fish in a domestic situation. Whilst it is possible to run such a tank on undergravel filtration, this becomes very uneconomic and an undertank trickle filter is not only going to prove cheaper, but also far more efficient at ridding the water of copious amounts of fish waste. A large, efficient protein skimmer must also be regarded as essential and will help tremendously with such high stocking levels. The correct wattage ultra-violet steriliser will help protect valuable livestock against disease, and activated carbon will clear the water of yellowing dyes that might otherwise spoil viewing enjoyment. On the subject of viewing, large tanks will require substantial lighting to illuminate the fish properly so that the impact of colours and patterning may become apparent. A 6ft tank will require at least four full-length tubes spaced equally across its width. I would choose, for instance, 3 x Lifeglo's and 1 x Marine Glo to accentuate blues, greens and black. Mercury vapour lamps are a reasonable option, but will supply a predominantly yellow light that must be sharpened up with either actinic tubes or Marine Glo's. Metal halides are an expensive, but ideal choice, and 2 x 150 watt lamps will give an intense natural light. The beauty of both mercury vapour and metal halide lighting is that they create a wonderful rippling effect over the rockwork and base of the tank; very reminiscent of natural sunlight.

Big fish need room in which manoeuvre and only the minimum amount of rockwork should be supplied. A reef wall may look impressive but it will take up important swimming space and displace valuable amounts of water. In all cases, the right balance must be struck for each particular species.

What is a Big Fish?

There are no rules governing what constitutes a big fish; however, any specimen that has attained 6" (15.2cm) when measured from the tip of the nose to the caudal peduncle must regarded as a good contender. 6" may not sound a great size (no smutty jokes please!!) but in reality this constitutes a respectable individual. Thereafter, specimens really do start to look big, especially as their girth starts to fill out as well. Some fish, of course, can measure 6" and still be small; our friends the Morays Eels are a good example (although these will also reach big fish status quite quickly). But these are the exceptions to the rule of thumb and most families e.g. triggerfish, large angelfish, some tangs, porcupinefish, batfish, squirrelfish, large wrasse, boxfish, lionfish, etc. will easily conform to our specifications.

There are a few fish in the trade that will eventually exceed the biggest domestic aquarium, most notable of these are the sharks. The smallest shark can be expected to reach 2 feet (60cm), while the largest may have a potential for 14 feet (420cm)! Far too large for even the most enthusiastic fishkeeper! At the moment, most public aquaria are swamped with unwanted sharks and the marinist must think long and hard before taking on such an enormous responsibility (even though it may initially arrive in a cute little egg pouch!). Needless to say, sharks and other unsuitable fish will not feature in my forthcoming selection.

Adult or Juvenile?

Ideally, a complete fish selection should be planned well in advance and all specimens introduced as juveniles. This procedure has several advantages: firstly, juveniles tend to be more forgiving than adults, especially of others in the same family and more importantly, feeding habits; secondly, a collection of juvenile fish all growing through to adulthood together is likely to be a much more peaceful, cohesive group, presenting far fewer compatibility problems for the owner; thirdly, biological filters can be allowed plenty of time to adapt to the increased loading placed upon them; and last, but not least, there is a great deal of pleasure to be had watching fish develop into a full-fledged adult from what might be a totally dissimilar juvenile. In all cases, patience is the key. For it might be several years before young fish start to look like big fish. The alternative is to plunge straight in and begin stocking with large specimens from the outset. If this route is followed, do not expect an easy ride! There are likely to be compatibility problems leading to fighting or general bullying, as well as dietary and water quality difficulties.