How to Add a Frog or a Crab to Your Freshwater Aquarium

If you are looking for a way to add diversity to your aquarium, consider adding a frog or a crab. African dwarf frogs are the most widely-available freshwater frogs and, because they are entirely aquatic, they adapt well to life in an established aquarium. Aquarium crabs come in a variety of shapes and sizes, but they are a little more difficult to keep in established aquariums because most species require access to land. The two most common species of freshwater aquarium crab are fiddler crabs and red-clawed crabs, and both are fairly easy to find in the aquarium trade.

  1. Frogs and Aquarium Fish

    • As suggested by their name, African dwarf frogs are fairly small -- especially as juveniles -- and large species of fish may regard them as prey. This being the case, it is wise to check that none of the fish in your established tank are large, predatory species. Cichlids and large gouramis, for example, may become aggressive toward aquarium frogs. African dwarf frogs are best kept in a community tank with small or medium-sized fish such as loaches and tetras. The clawed frog is another species sometimes seen in aquariums, but because these frogs are predatory, they are not recommended for the community tank.

    Tank Decorations for Aquarium Frogs

    • If your existing tank is sparsely decorated, add several smooth rocks or pieces of driftwood. These decorations will provide your frog with places to explore and hide. Add clumps of live aquarium plants to your tank if you do not already have some. Live plants will not only provide your aquarium frog with the cover it needs to feel secure, but they will also increase the oxygen content of the water.

    Tank Set-Up for Aquarium Frogs

    • African dwarf frogs typically grow to a maximum size of 2.5 inches and are best kept in tanks larger than 10 gallons in capacity. Install an aquarium heater, if you do not already have one in place, to maintain a stable water temperature. African dwarf frogs are most likely to thrive in steady tank temperatures between 72 and 82 degrees Fahrenheit. Lower the water level in the tank slightly and check to be sure your tank lid fits tightly. African dwarf frogs will escape if given the opportunity, and these precautions will help to prevent this from happening.

    Caring for Aquarium Frogs

    • Add African dwarf frogs to your tank in groups of three. These creatures feel more comfortable in a group, and multiple frogs will provide you with greater entertainment than a single frog. To keep your frogs healthy, feed them meaty foods on a daily basis. Offer your frogs frozen or freeze-dried foods such as brine shrimp, bloodworms and tubifex worms to satisfy their carnivorous dietary needs. Do not be concerned if your frogs appear to hide a lot during the day -- these creatures are naturally more active at night. Keeping the lighting in your tank subdued may encourage your frogs to be more active during the day.

    Fish and Aquarium Crabs

    • Because fish are part of the natural diet of many crabs, it is important to make sure that the fish you have in your tank will be able to stay out of the reach of your crabs. Fish that are particularly small, slow or have long fins are not recommended for tanks with aquarium crabs. If you are adding aquarium crabs to an existing tank, add only one or two crabs, and be sure the fish you have are small enough and fast enough to avoid capture. Most danios and tetras that have short fins and tend to swim in the upper levels of the tank can be kept safely with aquarium crabs.

    Species of Aquarium Crab

    • Fiddler crabs are one of the most common species found in the aquarium trade. These crabs are also sometimes referred to as mini crabs by aquarium hobbyists and are easily recognized by the large claws exhibited by the males of the species. Another species of aquarium crab is the red-clawed crab. Like fiddler crabs, red-clawed crabs come from brackish environments, but they can survive in freshwater tanks. If the fish in your existing tank are not likely to tolerate the addition of salt to the water, add red-clawed crabs to your tank rather than fiddler crabs.

    Tank Set-Up for Crabs

    • Most species of aquarium crabs require some access to air and dry land. To provide for these needs, add several large stones to your tank and keep the water level low enough so that the tops of these stones remain above the water level. Underwater, crabs need plenty of hiding places such as rock caves and driftwood. Aquarium crabs may also enjoy open areas of soft or sandy substrate in which they can burrow. One of the most important aspects of tank set-up for aquarium crabs is a tight-fitting aquarium lid because these creatures are excellent climbers and may escape if given the chance to do so.

    Caring for Aquarium Crabs

    • If you plan to keep fiddler crabs, you will need to add some salt to the tank water to simulate brackish conditions. The amount of salt needed may vary, but in general, 1 teaspoon of salt per gallon is enough. Because not all aquarium fish are able to tolerate salinity, check to be sure the species you already have in your tank will not be harmed by the addition of salt. If some of your fish cannot tolerate salt, you may need to transfer them to another tank or replace them with salt-tolerant species. Maintain your tank temperature between 74 and 84 degrees Fahrenheit using an aquarium heater. Feed your crabs a diet of flake foods and sinking pellets along with frozen or freeze-dried bloodworms and brine shrimp.