Marine Fish & Corals

Saltwater aquariums are more complicated than their freshwater counterparts. Marine tanks feature fish from extremely stable water. This means marine fish require more careful attention to their tanks just to survive, let alone thrive. Reef tanks -- saltwater tanks that prominently feature corals and other invertebrates -- are even more complicated. Corals and other invertebrates absorb calcium and other minerals from the water, requiring you to supplement the water with these minerals while making sure you don't upset another water parameter at the same time.

  1. Marine Fish Versus Freshwater Fish

    • All fish have adapted to their home waters. Marine fish hail from water of exceptional chemical stability. While most freshwater environs can range in water parameters, almost all saltwater fish need narrow ranges of water parameters, including a pH of 8.2 to 8.4 and a temperature 74 and 78 degrees Fahrenheit. Most freshwater fish have a larger range of preferred water conditions. Saltwater fish also need a salinity between 1.022 and 1.025. Also, marine fish need water free of ammonia and nitrite, while many freshwater fish can tolerate low levels for short times. Nitrate and phosphates should stay between 40.0 and .2 ppm respectively but ideally be as low as possible.

    Fish-Only Setups

    • Marine fish need more space than their freshwater counterparts. While freshwater stocking guidelines hold that you can keep 1 inch of aquarium fish length per gallon of aquarium volume, similar saltwater guidelines for saltwater hold that 1 inch of fish needs 2 to 4 gallons of water. In both cases, fish larger than 3 inches need special guidelines; research your particular species for the amount of space the fish will need. While experts have differing recommendations, most recommend a protein skimmer, a sump filter and live rock. Protein skimmers use mechanical processes to remove organic contaminates from the water. Sump filters, also called trickle filters or wet/dry filters, are supplemental containers of water plumbed to the aquarium to increase volume and allow you to attach equipment outside the tank. Live rocks are old, dead coral skeletons that have been colonized by other organisms.

    Corals and Reef Tanks

    • The leap in aquarium complexity between freshwater and saltwater fish is comparable to the leap between a marine fish-only setup and a reef aquarium. Corals have their own care requirements. Specifically, most corals need strong water movement and intense lighting. Reef aquariums typically feature supplemental water pumps and power heads to move water around. Since corals' cells contain photosynthetic algae that sustain them, reef tanks need at least 5 watts of lighting per gallon of aquarium volume. Typically, reef tanks use advanced aquarium lighting like T5 fluorescents or metal halide bulbs. On top of this, all coral -- both squishy soft corals and ridged hard coral -- absorb calcium from the water to build their support structures. You need to carefully supplement calcium, magnesium and other trace elements to the water to replace the minerals absorbed by coral and other invertebrates.

    Keeping Fish and Corals Together

    • Most reef aquariums feature fish. When selecting fish for a reef aquarium, you need to stick to species that will not harm invertebrates. For example, triggerfish, puffer fish and butterflyfish make poor candidates for reef aquariums, since they love eating expensive inverts. Other fish, like damselfish, clown fish and many gobies make excellent choices for reef aquariums without qualification. Other fish, like lion fish, may eat fish and mobile invertebrates like crabs but typically leave corals and other sessile inverts alone. You also have to pick invertebrates that will not harm each other with fish. Some crustaceans, like mantis shrimp and arrow crabs, can prey on other inverts and unwary fish. Compatibility is even more important with reef tanks, since marine fish and corals cost much more than freshwater aquarium pets.