Written by Gwen S. who works in Drs. Foster and Smith’s Technical Support Department.
Before the mid 1700’s Marine Sponges were thought to be plants; however, zoologists then classified them as Porifera, which mean “bearing openings.” There are three subspecies: Demospongiae, Calcispongiae, and Hyalpsponggiae. In these three subspecies, there are over 8,000 valid species of marine sponges. There are a few species that can be found in sand; however, most Sponges need to be attached to a hard surface. The life span of Marine Sponges can range from a couple months to 20 years. If a Sponge is injured or there is not enough food and it starts to disintegrate, it can regenerate itself. All it would need is a small fragment of the original sponge to grow into a new Sponge.
They do not have tissues or organs and are considered to be the simplest form of multi-cellular animals. The body of a Marine Sponge has pores on the outside known as Ostia and there are larger pores internally known as Oscula. The Flagellum is what forces the water (food) in and out of the Sponge.
Marine Sponges feed on particles sizing from several microns to smaller than a micron; although, zoologists have found a few species that have been known to consume smaller shrimp.
They are known to reproduce both sexually and asexually. There are some that develop planktonic young and others that are fertilized and develop internally. Others will release eggs and sperm into the water. The baby Sponges can float through the water for several days before attaching to a hard surface.
Marine Sponges are likely the most common hitchhiker in live rock, but most people have no idea they are there. You would have to actually break apart the rock to find out if there are Sponges inside. Sponges will actually filter out ammonia and nitrogen from the large amounts of water several times per hour, without competing for food such as Phytoplankton that is added for other filter feeders in the tank. For this reason, some species of Marine Sponges can be beneficial to the home aquarium. There are also a number of different species that should not be kept in reef tanks – one example would be from the family Spirastrellidae. These Marine Sponges will bore into SPS corals, as well as live rock. If this species of Sponge were to bore into an SPS coral or live rock, it will cause the coral and rock to disintegrate. One species will actually protect SPS corals from boring Sponges: the Orange Icing Sponge (Mycale laevis).
Keeping Sponges in a Saltwater Aquarium Environment:
Keeping Sponges is difficult and should only be done by an experienced enthusiast. When Marine Sponges are maintained in dedicated non-photosynthetic aquariums that are fed properly, they can make a great addition to these types of displays. The hardest part of keeping a Sponge is actually getting it into the tank. If a Marine Sponge is removed from water, air can become trapped in the atria and the Sponge will die. Once introduced into the tank, most sponges will require low lighting to reduce the changes of algae growing on their outer tissue as well as good water flow. They will also need to be clean of any debris or algae that land on or attaches to the Marine Sponge.
Placement of the Marine Sponges is also important because they can engage in “chemical warfare” just like soft corals. They should be kept away from hard corals since encrusting Sponges will continue to spread unless stopped by substrate. Another reason housing them in reef tanks is difficult is the filtration. Silicate-removing chemical media, a skimmer that is rated for a much larger aquarium, or a UV Sterilizer that removes particles is essential to the survival of Marine Sponges. Use caution with Sponges as they can pollute your aquarium water as well as produce a very powerful sting. Certain species of Sponges can be fragged from a healthy colony and attached to a piece of rock by using fishing line after they are well adapted to captive conditions in the home aquarium.
If you think Marine Sponges might be right for your aquarium, you can find several species of Sponges available on our LiveAquaria.com website. In addition, our WYSIWYG Diver’s Den Invert Section features many spectacular Sponges. These are available only as one-of-a-kind, so subscribing to our Email Alerts will allow you to know when one is being added.
For the advanced marine aquarist who is knowledgeable and familiar with their specialized requirements, Marine Sponges can make for an interesting addition to a dedicated non-photosynthetic marine aquarium that is fed foods designed for filter feeding invertebrates and planktonic feeding soft corals.