Fishes Suitable for the Invertebrate Aquarium
by J. Charles Delbeek M.Sc.

One of the main criticisms of the minireef has been that many of the
more popular fish such as butterfly- and angelfish cannot be kept in
such setups due to their habit of feeding on the invertebrates and
macroalga. What one tends to forget is that there are still many
beautiful fish species available to the hobbyist. Up until now, we
have not been exposed to many of these species because the demand for
them has not been great and/or they were difficult to keep in
conventional setups. With the increased popularity of "natural"
systems we are starting to see more of these fish imported by both
wholesalers and retailers. In this series of articles I will
introduce you to some of the fish which can be successfully kept with
invertebrates.

Genus Nemateleotris
There are three species within this genus, two of which are commonly
seen while the third is very rare at present:

1) Nemateleotris magnificus, the Firefish or Fire Goby, is easily
identified by its elongated first dorsal spine. This spine can be as
long as 2/3 of the body length in some individuals. The front half of
the body is a creamy white which gradually darkens to dark red at the
end of the body. Along the top of the head there is a light purple
stripe. In some individuals the head may have a yellow
tinge, too. The maximum size for this species is approximately 6 cm.
This species is commonly found in most pet stores and can range in
price from $15- 30 depending on availability. These fish were thought
to be very rare in the early 70's but have since been found to be
abundant in the Indo-Pacific area. This is a very peaceful and shy
fish and as such they do not react well to very active fish. They
should be kept with other peaceful inhabitants such as bogies,
mandarins and blennies. If the other fish in the aquarium are too
active, the firefish will spend very little time in the open. In
keeping with their shyness, they tend to do better in small groups of
3-6 individuals. Although they do well in groups, one individual may
become overly aggressive towards the others and kill them off one by
one (Achterkamp 1986). In some cases only a pair will remain and they
will then settle down to a peaceful existence. In this case DO NOT
add any more! In a peaceful aquarium, N. magnificus will tend to
remain in the open a great deal of the time but they will have dug
out a hiding place under a rock to which they can retreat when
threatened. In some cases they will also bury themselves in the
substrate just like wrasses do at night (Achterkamp 1986). Feeding
these fish is no problem as they readily accept most foods such as
frozen and live adult brine shrimp, flaked food and just about
anything else you can think of. The only requirement is that the food
must be moving in the water column, either on its own or by the water
movement caused by your filter. It is best to feed them at least
twice a day as they tend to require large quantities of food to be at
their best (Mayland 1977). In summary, this species is highly
recommended for the beginner, although the water quality should be at
the high end of the scale. They are surprisingly disease resistant
and if they survive the first week in your tank they will usually
last a long time. The only thing to watch out for is that they tend
to be jumpers, therefore you should take precautions to block any
openings above the aquarium and over your overflow (Achterkamp 1986).
This is best accomplished by fiberglass fly screening over the
overflow and aquarium.

2) Nemateleotris decora differs from N. magnificus in a number of
ways. First of all, although the first dorsal fin is elongated it is
nowhere near as elongated as in N. magnificus. Secondly, N.
decora has a much different color pattern. The base color of the
body is dark greenish- blue extending from the head to a dark blue
near the tail. There is also a dark purple stripe extending across
the face and along the dorsal surface. In addition, the second dorsal
fin, anal fin, tail fin and pelvic fins have a bright red trim. Much of what was
written about the behavior and feeding of N. magnificus holds for
N. decora, too. However, N. decora tends to
be much more aggressive than N. magnificus and does not usually do
well in small groups (Achterkamp 1986). Although N. decora is not
as shy as N. magnificus, they still do not like to be in aquariums
with active fish. One thing to be aware of when buying these fish is
that they come from deeper water than N. magnificus. This means
that care must be taken in decompressing them carefully so as not to
damage their swimbladders when they are brought to the surface. The
normal swimming posture of N. decora is with the head pointed
slightly upward towards the surface. If the fish is swimming in jerky
movements with its head pointing towards the substrate, then chances
are good that it is suffering from some sort of swimbladder problem
(Achterkamp 1986). This behavior is a sign of swimbladder problems in
ANY fish which has been collected from deep water and brought up too
quickly. Watch for it!

3) The third species, Nemateleotris helfrichi, has only recently
been described (1980), let alone photographed (1988). It is similar
in appearance to N. decora but its color pattern is much different.
The base color of the body is a light blue-purple with a yellow head
and tail. The dorsal, anal and pelvic fins have yellow and dark blue
horizontal stripes with orange spots in the blue stripes. Along the
front of the head, extending along the dorsal surface and up the
first dorsal spine is a bright pink line. In the middle of this pink
line is a light blue one which also extends up onto the first dorsal
spine. The eye is yellow with a pink line through the top of it . These 
jewels come from the central Pacific, namely the
Tuamobu-Archipelago and the Society and Palau islands (Dekker 1988).
Early accounts appear to indicate that this species is as hardy as
the other two and may even be more aggressive than N. decora
(Dekker 1988). Also, it is just as shy and does NOT tolerate active
fish, such as wrasses, in the same aquarium.

Any of the three above mentioned species will do quite well in an
invertebrate aquarium as well as a conventional one, and are a good
bet for the beginner. Just remember NOT to put them into an aquarium
with active fish.

Next issue: The Dwarf Basseletts (Pseudochromidae).

References
1. Achterkamp, A. 1986. Bewust kiezen ... een serie praktische
aquariumtips/4: Slaapgrondels (Eleotridae). Het Zee-Aquarium 36
(5):92-97. (Dutch)

2. Dekker, L.N. 1988. De derde soort! Nemateleotris helfrichi. Het
Zee-Aquarium 38(2):30-31. (Dutch)

3. Mayland, H.J. 1981. Koraalvissen and lagere dieren: Van het
tropische rif nar het aquarium. Thieme and Cie, Zutphen. (Dutch).