I found a couple of abstracts about feeding and growth. Unfortunately, they are not new but are still worth the short read.
Article(HTML): Growth and mortality of common octopus (Octopus vulgaris) fed a monospecific fish diet.... the low AE values of the present study
support that, for octopuses, high-lipid diets are less
efficient and have a reduced capacity for growth in
comparison to low-lipid and high-protein diets.
Full Article (PDF or URL): The use of alternative prey (crayfish, Procambarus clarki, and hake, Merlucius gayi) to culture Octopus vulgaris (Cuvier 1797)Because cephalopods have a very low lipid digestibility (O'Dor et al. 1984, Lee 1994, Mazon et al. 2007), high quantities of lipids in the digestive tract may obstruct the absorption of amino acids, thus affecting growth (Garcia Garcia & Cerezo Valverde 2006). Fatty diets such as mackerel and sardine might certainly not be sufficient for the good nutrition of octopuses, and complements should be necessary.
The results indicate that crayfish is not an adequate replacement for the usual prey to fatten octopus... None of the 36 octopuses died during the experiment. A higher final weight was registered in octopuses fed squid than in animals fed crayfish