I have been looking at the fat and protein content of craw/cray fish to see how close they compare in fat and protein to marine food. If I did the math correctly, this should be close.
100 grams Cray/Crawfish .. Lobster ....... Crab ........ Shrimp
Protein ....... 15.0 ................ 26.4 ............ 20.0 .......... 21.2
Fat ................ .5 .................. 1.3 ............. 1.8 ............. .88
Unfortunately, I don't know the optimum ratio but it would suggest that a full time diet of crayfish would lead to an animal eating more but getting less. If this is the case, I wonder how it fits into Roy and Joe-Ceph's thoughts that fewer feedings extend the octos (at least the bimac's) lives.
Aquarium Invertebrates: Nutritional Value Of Live Foods For The Coral Reef Aquarium, Part 2
By Rob Toonen, Ph.D.
discusses the differences. Here is part of the article
100 grams Cray/Crawfish .. Lobster ....... Crab ........ Shrimp
Protein ....... 15.0 ................ 26.4 ............ 20.0 .......... 21.2
Fat ................ .5 .................. 1.3 ............. 1.8 ............. .88
Unfortunately, I don't know the optimum ratio but it would suggest that a full time diet of crayfish would lead to an animal eating more but getting less. If this is the case, I wonder how it fits into Roy and Joe-Ceph's thoughts that fewer feedings extend the octos (at least the bimac's) lives.
Aquarium Invertebrates: Nutritional Value Of Live Foods For The Coral Reef Aquarium, Part 2
By Rob Toonen, Ph.D.
discusses the differences. Here is part of the article
6) Freshwater Crustaceans
If you remember back to the start of the article, I went on a rant about using freshwater fishes to feed to your saltwater pets. Now, all the sudden you're reading a section about freshwater crustaceans in an article about feeding saltwater animals - what gives!? Well, the nutritional profile of freshwater crustaceans is actually surprisingly close to that of marine crustaceans (Tables 1 & 2).
Table 1: Total amount of various nutrients in a 100g sample of tissue from selected species of potential food fish as compiled by the US government (Dept of Agriculture) for nutritional comparisons of foods that are available to consumers.
Table 1: Total amount of various nutrients in a 100g sample of tissue from selected species of potential food fish as compiled by the US government (Dept of Agriculture) for nutritional comparisons of foods that are available to consumers. Food Fish Energy Protein Total Lipid Vit. B complex Vit. C
Freshwater fishes
Catfish 565 kj 15.55 g 7.59 g 3.5 mg 0.60 mg
Carp 531 kj 17.83 g 5.60 g 2.8 mg 1.60 mg
Anadromous / Brackish fishes
Wild Salmon 594 kj 19.84 g 6.34 g 11.0 mg 0
farmed Salmon 766 kj 19.90 g 10.85 g 10.0 mg 3.90 mg
Striped Bass 406 kj 17.73 g 2.33 g 3.3 mg 0
Marine fishes
Cod 343 kj 17.90 g 0.63 g 2.5 mg 2.90 mg
Snapper 418 kj 20.51 g 1.34 g 1.5 mg 1.60 mg
Freshwater crustaceans
Crayfish 301 kj 14.85 g 0.97 g 2.6 mg 0.50 mg
Marine crustaceans
mixed Shrimp 444 kj 20.31 g 1.73 g 3.0 mg 2.00 mg
Spiny Lobster 469 kj 20.60 g 1.51 g 4.8 mg 2.00 mg
Unlike the freshwater feeder goldfish comparison with marine fish, in which the fat content can be more than 20 times higher than the natural diet, freshwater crustaceans are actually slightly lower in both fat and Vitamin C content, as compared to marine crustaceans (Tables 1 & 2). There are other differences, too, but in this case, the deficiencies can be easily compensated for by using a commercially available HUFA supplement, because the freshwater crustaceans tends to be roughly equal, or perhaps a bit lower in saturated fat as well as essential fatty acids than the marine prey that make up the natural diet (Table 2). This major difference makes the use of freshwater crustaceans a much better option than freshwater fishes for feeding to your marine aquarium.
Table 2: Amount of saturated fat and a number of essential highly unsaturated fatty acids (HUFA) for each of the species groups listed in Table 1. Values for Saturated fats, LA (Omega-6, linoleic acid - 18:2), ALA (Omega-3, alpha- linolenic acid - 18:3), EPA (Omega-3, eicosapentaenoic acid - 20:5), and DHA (Omega-3, docosahexaenoic acid - 22:6) are again measured in grams from a 100g tissue sample as presented in Table 1, above. These fatty acids are among those typically included in HUFA enrichment products to supplement the diet of marine fishes in captivity. Small, non-zero numbers are denoted by < 0.01.
Table 2: Amount of saturated fat and a number of essential highly unsaturated fatty acids (HUFA) for each of the species groups listed in Table 1. Values for Saturated fats, LA (Omega-6, linoleic acid - 18:2), ALA (Omega-3, alpha-linolenic acid - 18:3), EPA (Omega-3, eicosapentaenoic acid - 20:5), and DHA (Omega-3, docosahexaenoic acid - 22:6) are again measured in grams from a 100g tissue sample as presented in Table 1, above. These fatty acids are among those typically included in HUFA enrichment products to supplement the diet of marine fishes in captivity. Small, non-zero numbers are denoted by < 0.01. Food Fish Saturated Fat LA (18:2) ALA (18:3) EPA (20:5) DHA (22:6)
Freshwater fishes
Catfish 1.77 0.88 0.10 0.07 0.21
Carp 1.08 0.52 0.27 0.24 0.11
Anadromous / Brackish fishes
Wild Salmon 0.98 0.17 0.30 0.32 0.29
farmed Salmon 2.18 0.59 0.09 0.62 1.29
Striped Bass 0.51 0.02 0.02 < 0.01 < 0.01
Marine fishes
Cod 0.08 0.01 < 0.01 0.08 0.13
Snapper 0.28 0.02 < 0.01 0.05 0.26
Freshwater crustaceans
Crayfish 0.16 0.08 0.03 0.12 0.03
Marine crustaceans
mixed Shrimp 0.33 0.03 0.01 0.26 0.22
Spiny Lobster 0.24 0.01 < 0.01 0.27 0.11
This is fortunate for most of us, because in most places small freshwater crustaceans are much easier to come by than their marine cousins. I'll discuss some of the most common and easily available of these below and explain the potential drawbacks to using them as a food for the inhabitants of your marine tank.