Fishes Database         ReefKeeping 101

Fish are the only vertebrates kept in the reef tank.  Selection of fish for the reef tank has to take in several considerations.

• Is it going to eat any of the invertebrates you are trying to keep?

• Will it get along with the other fish in the reef community you are keeping?

• Will it grow too large or otherwise be disruptive to the reef community you are keeping?

• Can you provide for its nutritional or other specialized requirements?

• Does it add value i.e. a herbivorous fish will help to keep algae under control?

• Overall fish bioload of the tank.

Reef tanks provide the opportunity to keep fish in a more natural environment and fish tend to be healthier and have less outbreaks of disease when kept in a reef tank.  This is good, since you cannot treat fish for disease in the reef tank and they are almost impossible to catch and remove for treatment outside the tank because of all the hiding places the live rock affords.

Fish that feed on other fish, large crustaceans or corals are generally unsuitable for the reef tank for obvious reasons. 

Some fish do not tolerate others of their own kind very well.  Tangs are notorious for this problem.  Even though tangs are some of the best reef inhabitants, adding more than one requires attention to how closely the new tang looks like the current inhabitant.  The more they look alike, the more likely there is to be trouble.  Other fish tend to just be aggressive in general and may chase and harass any other fish around it.

Some fish tend to get too large for the reef tank.  This is mostly a concern when setting up a small tank less than about 70 gallons, but some fish really need tanks greater than about  125 gallons to do well long-term.  Other fish may burrow through or sift the sand looking for food and may dislodge the live rock structure.  Other fish, such as the Dragon Wrasse will actually pick up small pieces of rock and flip them over looking for morsels of food living beneath.

Some fish have very specialized nutritional requirements.  The most common example is the Mandarin fish.  These fish generally only eat small crustaceans and other life which grow in the wild and in  the sand and rocks of reef tanks.  The good news is that a reef tank finally provides the ability to keep these fish in healthy condition, the bad news is that it requires about a 70 gallon tank to grow enough natural food for one Mandarin fish.   Other fish have other specialized needs.  Some sift through the sand for their food and may not get enough nutrition if they will not also accept prepared foods.

It is good to include some herbivorous fish, such as tangs, in the reef tank to help keep algae in check.  These fish contribute to the community by getting at least part of their nutrition from the tank itself.  Other fish, such as clownfish for instance, tend to eat only food that is provided by the reef keeper and as such add more of a biological load to the tank.

Fish, unlike corals or clams, tend to pollute their environment so care must be taken to not over-load the system.  The common logic has been to keep fish load extremely low and to feed lightly to minimize the effect of the fish on the tank.  Recently, there is evidence to suggest that high demand systems can more rapidly utilize the wastes from the fish and allow for a higher fish stocking level than has normally been kept.  To generalize, a new tank should restrict the fish stocking to low levels.  As the tank matures, the stocking level can be increased slowly while care is taken to ensure the tank is not getting overstocked.  What overstocked means is obviously a loaded question and I will propose that somewhere between about 2" and 3" of fish per 10 gallons of tank volume is getting up there.

See acclimation procedure for further information on introducing fish to the tank.