Being almost completely immobile, sea sponges aren't going to provide much entertainment with their antics, but they do come in a vast array of forms and colors, providing aesthetic appeal if not much in the way of personality. Although they're pretty simple animals, their care is sometimes anything but. Sponges tend to be ultra-sensitive to water chemistry and movement, and not all species are suitable for beginners.
The history of your sponges may determine whether they live or die in your tank. Carelessly harvested wild sponges, especially those that have been exposed to air, may die within days. Sponges can’t cope with rough treatment or, usually, with being removed from the water. Because sponges can reproduce asexually by division, some species are relatively easy to “breed” in captivity. In fact, they don’t actually have tissues or organs, meaning it's possible for a hobbyist to divide up a sponge as you might a plant, producing a number of completely healthy separate sponges. For this reason, the Fish Channel notes, the best source for new sponges might be another hobbyist, rather than an aquarium store. Otherwise, check the condition of the sponge carefully and ask the store where it came from, how it was harvested and transported, and how long the store has had it. If the sponge looks discolored and soggy or staff members don’t seem able or willing to answer your questions, go elsewhere.
Most of the 5,000 or so known species of sponges are saltwater creatures, including nearly all sponges available in the aquarium trade. There are a few freshwater sponges, but they're nowhere near as colorful as their marine cousins. To keep most sponges, you’ll need an established saltwater tank. The temperature, amount of light and water parameters vary depending on the species, so take care to select a sponge that suits your tank. If have your heart set on a species requiring a different environment to that of your current aquarium, set up a dedicated tank, remembering that cycling takes as long for sponges as it does for any other sea creature.
Sponges might be sessile but they're not plants and don't photosynthesize. Some species are associated with symbiotic photosynthesizing algae or bacteria, but not all. Such sponges can’t create any of their own food -- they have to get it from the water. They filter out phytoplankton, other microorganisms and particles. Because they can’t move much, you must ensure the food moves to them. An established tank with a steady flow of water and sufficient light should supply most of your sponge’s needs. Supplemental food, crucial in a small tank, in the form of plankton infusions is widely available from aquarium suppliers.
Some species of sponges are endangered, and harvesting for the aquarium trade doesn’t help matters. If you decide to acquire wild-caught sponges or those of uncertain origin, only choose common species. Sponges won’t get on well with all other marine creatures. Some are vulnerable to predation by carnivorous fish and invertebrates, while others can release lethal toxins when stressed. Sponges aren’t decorative rocks -- you need to check their compatibility with existing or future pets as carefully as you would for any other additions to your aquarium.
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