My sponge is shrinking…

Any thoughts? Should I remove it? I can tell that it doesn’t stink or anything (by touching it, not taking it out) but it is shrinking.

Dear Carrie:

Yup, that’s a fairly common problem with live sponges in the aquarium. They are filter feeders that typically feed on very small particles such as bacteria and other microbes, and there is simply not enough suitable food for them in most standard aquarium systems. Live sponges do best in large, well-established reef systems with good flow and no protein skimming.

It would appear that your shrinking sponge is simply not getting enough to eat and therefore losing mass as a result. This in itself is not harmful to your seahorses or the other aquarium inhabitants, but should the sponge expire, it could present a threat due to deteriorating water quality and/or the release of toxins into the water as it disintegrates. So it’s generally a good precaution to remove a live sponge when it begins to dwindle away.

That doesn’t mean that your seahorses have to do without sponges, however, Carrie. The latest generation of artificial sponges are so lifelike the seahorses can’t seem to tell the difference. They are cast from molds of actual sponges and are very detailed and realistic. They are made from polyurethane, which gives them a flexible, resilient texture that’s very similar to the living sponges and they are therefore just as attractive to the seahorses as hitching posts. The synthetic sponges are available in a variety of bright colors such as yellow, orange, purple, blue, and red. So I would find myself a colorful artificial tube sponge or finger sponge or tree sponge or two to replace your shrinking specimens if I were you, Carrie.

Best of luck with your seahorse tank and it’s decor, Carrie!

Happy Trails!
Pete Giwojna

Dear Carrie:

Yes, indeed, the polyurethane that is used to make these synthetic sponges is totally inert in saltwater and completely non-toxic. They are perfectly safe to use in the aquarium. There are several different types and sizes of artificial sponges available and they can be obtained from quite a number of places online, but one that is familiar to most hobbyists is Drs. Foster & Smith, which offers some very realistic, colorful tube sponges:

Click here: Aquarium Decorations & Ornaments for Home Aquariums: Artificial Sponge Aquarium Decorations
http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=12582&cm_mmc=Shopping%20Portal-_-Sortprice-_-Fish-_-4-1/2%20x%205-3/4%20x%204-1/4%20high&ref=4060&subref=AA

Although these polyurethane sponges are designed for aquarium use and are altogether safe, there is one thing the hobbyist needs to be conscious of when using them. Don’t broadcast feed or scatter-feed frozen Mysis when you are using these tubes sponges in the aquarium. Scattered feeding is never a good idea in the first place, but it is particularly ill advised around the fake sponges because there is a chance that frozen Mysis can settle in the opening of the tubes where it would be inaccessible to the seahorses or the aquarium janitors. If that happens, the trapped Mysis would begin to decay and could soon degrade your water quality. So it’s important to target feed your seahorses away from the tube sponges, or to teach them to eat from a feeding station instead in order to avoid any such problems.

Staghorn coral skeletons are also safe to use and look perfectly natural in a marine aquarium, so that’s another good option you can certainly try, Carrie. The coral is not at all too rough or scratchy or abrasive for seahorses and they will gladly use the branches as hitching posts. The only drawback is that the pristine staghorn coral skeletons look beautiful at first but don’t stay that way for long. They do indeed get overgrown with algae and I find that it’s almost always the unattractive brown stuff, which can be rather unsightly. When that happens, cleaning the coral skeletons is more difficult than the artificial decorations.

Best of luck with your aquascaping, Carrie!

Happy Trails!
Pete Giwojna