Not a good sign: this
Assessor larva (day 1) is
lying on the bottom—
healthy larvae swim
freely at this stage.
(2009). It took me a total of eight attempts before I was
able to get the first six fry through metamorphosis.
EquipmEnt
I should note here that I use only very simple equipment—no special larval rearing tanks, no complicated
plankton cultures. I just feed phytoplankton (
Nannochloropsis salina) and the usual rotifers (Brachionus pli-catilis). But because I had problems with contaminated
Nannochloropsis on a number of occasions, I also used
“AlgaGen Phycopure,” a live phytoplankton mix, as backup. The rearing tank was a 5-gallon (20-L) aquarium kit
for freshwater shrimps, with the back and end glass sides
blacked out. The tank was placed on a dark blue base.
Food For rEaring
The Brachionus were cultured in two 1.3-gallon (5-L)
buckets and fed with Nannochloropsis. They were en-
riched prior to use by putting 1/5 gallon (0.7 L) of the
culture liquid in a 2/5 gallon ( 1.5-L) water bottle made of
PET plastic, with a drop of “INVE Selco Easy DHA” added
and the whole then “incubated” for around four hours.
The rotifers were strained off using a 55-micron gauze
prior to feeding. However, during the first experiments
I worked with an emulsion of egg yolk, fish oil, and Li-
povit. By chance I discovered that the larvae would snap
up Artemia nauplii as early as the fourth day, though I
am unsure whether they were able to digest them at this
early age. During my first successful rearing attempt I
added nauplii starting on the sixth day but didn’t com-
pletely stop feeding Brachionus until the 16th day. The
nauplii were again enriched with “Selco Easy DHA” in
the refrigerator for 12 hours.
HatcHing tHE larvaE
The larvae hatch after five nights. Because brooding
males remain well hidden, the aquarist often doesn’t get
to see the spawn. Hence it is sensible, in order to know
when to expect hatching, to note when the male disappears and work on the basis of five nights to fruition.
The larvae can be readily enticed to the surface with a
flashlight or dim light bulb and then caught out.
tHE First days oF liFE
In the first days the only equipment in my rearing tank
was a heater-stat and an airline. The larvae apparently
appreciated a relatively strong current without any diffuser. During the first days of life of the fish larvae the
Left: Larva of A. flavissimus on its first day of life. The grid ( 5 mm)
is for purposes of scale.
Right: In the first hours after hatching Assessor larvae still have a
prominent yolk sac that ensures their survival until they are able
to take their first food.
