Sponges in a Saltwater Aquarium

General info

Sea sponges are some of the most unusual life forms that can be found in the ocean. In marine aquariums, they are our allies in water filtration. They often grow wild in shady places under rocks, in sumps or on the surface of living rocks.

Sponges are very simple animals – they do not have a nervous system, tissues or organs. Their body is characterized by high porosity.

There are many species of sea sponges in nature – their number is estimated at 10-15 thousand. And since there are so many of them, it’s obvious that they differ in shape and size, among other things. Some species reach a maximum of several millimeters in length, and others – up to 2 meters. The latter are individuals that live at great depths in warm waters. Most often, however, sponges are found in warm sea waters in shallow coastal zones. In the wild, they grow in huge colonies.

These inconspicuous creatures lead a sedentary lifestyle. They attach themselves to the substrate with the help of appendages growing in the lower part of their body.

Sponges have no organs or nervous system. They are made of collar cells, equipped with single flagella. And these flagella, located on single cells, force the flow of water with oxygen and food particles through the spongocoel (the internal cavity of the sponge connected to the pores). The water then goes to the archaeocytes where final digestion takes place.

Sponges reproduce in two ways:

  • sexual reproduction: sperm excreted into the water through the internal cavity of the sponge reach sponges of the same species and are transported to the egg cells. The fertilized egg turns into a larva and is released into the water. The larva settles on a suitable substrate and slowly transforms into a miniature sponge;
  • asexual reproduction: budding, fragmentation and production of gemmules (circular masses of cells from which a new sponge emerges).

Wild sponges make their home in dark places, often under rocks in the aquarium. They reach a maximum of 2 cm in height, and their structure and color are rather inconspicuous, so they’re usually difficult to notice.

On the other hand sponges, such as Stylotella Aurantium, available in specialist aquaristics shops, can be really attractive and eye-catching in a marine tank.

In the natural environment, Stylotella Aurantium inhabits shallow coral reefs. In an aquarium, it’s a great addition if you want your tank to look more colorful. It can be used to fill empty spaces, especially dark ones, as these animals do not photosynthesize. In addition, due to the water filtration function, it’s good to place the sponge in a strong water flow.

These sponges, native to the Pacific Ocean, can grow up to 30 cm in size. A sudden change in temperature is not dangerous to them, but rapid changes in salinity can negatively affect their condition. When moving them to the aquarium, it’s important that they don’t come into contact with the air, as this can clog the pores through which the animal takes in food.


Sponges feed on plankton and bacteria, so, as I mentioned earlier, they should be placed in a place with a strong flow of water. In this way, we will enable them to catch food.


Sponges are very useful animals in a marine aquarium. They not only filter the water from the organic microsuspension, but thanks to the production of gametes, they perfectly nourish the corals. They feed themselves silicon, which is why they are a natural food competition for diatoms.

Sponges most often get transported into a marine aquarium together with the live rock they live on.

In aquarium stores you will find various types of sponges, but it’s vital to know that those more attractive ones usually don’t do so well in the aquarium. It’s difficult to provide them with the right food – microplankton. Also, too much detritus in the water can clog the sponges’ spines, causing their tissues to die. Sponges also feed on bacteria, and dosing with phytoplankton helps maintain them. Sponges don’t like dirty water. Many beginner hobbyists neglect the sponge by not providing enough water movement, which can lead to death of the organism.

There are quite a few sponges that require specific treatment. In general, however, it can be assumed that for sponges to survive in a marine aquarium, you need to provide them with appropriate food, including silicon and phytoplankton. Another thing would be good water flow which also positively affects the sponges. It’s important to keep an eye out on detritus settling on their surface, as it’s not conducive to them.

Air exposure

Sponges are full of tiny tubules. When you take the animal out of the water, the liquid will drain to some extent and will be filled with air instead. Due to ocean outflows, several types of sponges have adapted to temporary exposure to air, but most sponges do not tolerate such exposure at all.

Sea sponges – are they toxic?

Sponges as living beings use their toxicity to compete with other animals. Their bright red, orange and yellow colors indicate that the sponges produce very toxic compounds. They can release compounds into the aquarium water that cause, for example, coral bleaching.

About the author

Picture of Marek Protasewicz

Marek Protasewicz

Reefkeeping has been my passion for over 10 years now. I love learning. The hobby has taught me many valuable lessons, patience being the best example.
Combining work and passion is my path. I run Crazy Coral, a marine aquarium shop, for a number of years. Building this business from the scratch I learnt from my own mistakes at a heavy cost.
Later I managed a project aimed at development of methods for quick growth of Corals in non-natural conditions. The project was carried out by Get Sales, Poland.
Presently, I am responsible for distribution strategy at Reef Factory, of which I am a
co-founder. The company produces smart devices for marine aquaristics.
The last projects I have been involved in are Social Reef and ReefPedia.

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