I use Zoe Marine from Kent. Read that Zoecon is just as good.
Zoe Marine: Kent Zoe is a superior vitamin complex for Marine Fish, Invertebrates, and desirable algae. (Zoe does not contain phosphates as most competing vitamin supplements do, and will not cause unsightly algae growth!) It contains aquaculture grade vitamins, meaning that they are still active after one year in your aquarium! It is unique because it also contains natural minerals from spirulina and kelp sources. Competing products are preserved with glycerin, which is an alcohol and requires 50% concentration to preserve. Zoe is properly preserved, using less than ½% preservatives, yet has a 4 year shelf life with no refrigeration. Just smell the difference!
Zoecon: Diets deficient in omega-3 fatty acids can promote head and lateral line erosion (HLLE) syndrome in freshwater and marine fishes. Zoecon provides essential marine omega-3 fatty acids EPA and DHA. Enriches foods for saltwater and freshwater fishes. Contains shark liver oil, which contains natural immune system stimulants. Useful in raising fish and invertebrate larvae, as well as fortifying live food for juvenile and adult fishes and invertebrates. Phosphate and nitrate free, and contains no yeast or sugars!