38 9. Regular maintenance Staple diet Marine fish require much more iodine and other minerals than freshwater fish. More than 50 ingredients in sera fish food ensure feeding the aquarium inhabitants a balanced diet according to nature. This supports dis- ease resistance and prevents deficiencies. All sera foods are very low in phosphates and very easy to digest, thus preventing wa- ter pollution by undigested breakdown prod- ucts. 9.1 Feeding sera marin coraliquid, a plankton based liquid food rich in energy, was specially developed for filtrating inver- tebrates. sera marin GVG-mix is a flake food with added treats for marine fish. This versatile basic food contains iodine and other minerals from ma- rine algae, krill, plankton and other valuable ingredients such as bloodworms, daph- nia and Artemia shrimps.