I've just copied this post from another thread here called 'rearing octopus'. I would not have thought the Artemia would have been of any use, and would have, as Colin suggested, procured crab/shrimp larvae; I'm pleasantly surprised you still have many left alive - have you seen them attack and actually consume the Artemia? Do they still have residual yolk reserves? Please post notes on progress.
Jean, I'd be interested to know what sort of tank you were using (material, dimensions, volume, shape, colour), lighting, circulation pattern, flow rate etc, even if everything goes belly up. This sort of information is just as important as information on successful tank setups; I wouldn't have used Artemia, but there's more to this than food type (we'll be keeping larval octopus live soon).
See below (repeat posting)
Itami, K.; Izawa, Y.; Maeda, S.; Nakai, K. 1963: Notes on the laboratory culture of the octopus larvae. Bulletin of the Japanese Society of Scientific Fisheries, 29(6).
Abstract (slightly abridged; I've left the English as it was given it's largely a quotation).
The larvae of the Japanese commercial octopod, Octopus vulgaris, were successfully reared from the swimming larvae just after hatching to the benthic young octopus in 33 to 40 days on a diet of the zoea larvae of the shrimp, Palaemon serrifer. The rearing experiments were carried out at the Hyogo Prefectural Fisheries Experimental Station from June to September, 1962. At the start of the experiments 200 individuals of the octopus larvae were kept in a glass vessel containing about 8 litres of sea-water. During the early 20 days period the sea-water of each vessel was aerated and renewed every 3rd or 4th day, and after this period the method was changed for the use of running water. The results obtained are summarised as follows:
1) From just after hatching, the larvae of the octopus were fed on the larvae of Palaemon of 2 to 4 mm body length. After transforming into benthic stage, they were given a small piece of ovaries, testes and hepatic glands of the crab, Charybdis japonica. Three or four days after transforming, they were fed on small shrimps and young crabs, Gaetice depressus of 5 to 7 mm carapace width. It was observed that the young octopus of 30 mm total length ate 4 or 5 young crabs in a day.
2) The survival rate of the octopus larvae was found as low as 9 percent through the free-swimming stage. However, it would be conceivably possible to raise this survival rate much higher if sufficient food supply is secured during the rearing experiments.
3) It was found that the larvae settled on the bottom 33 to 40 days after hatching, when they attained a size ranging 10~15mm in total length (3.8~5.7 mm in body length). Once the swimming larvae transformed into the benthic young octopus, they became nocturnal and fed on foods mainly at night. A considerable mortality occurred among the young octopus, which was caused by cannibalism and creeping out of the rearing water.
4) The numbers of suckers found on each arm were 3 at hatching, 5 (4~6) at 10 days, 9 (6~12) at 20 days, 19 (16~22) at 30 days, 24 (21~27) at 40 days and 22~23 when a majority of octopus larvae grew to the benthic stage.