I think what you are saying is that you would rather add phytoplankton to feed everything in the tank? The problem is, sponges only eat bacteria so far as I recall (somebody correct me if I'm wrong). I wasn't disputing the idea of adding phytoplankton, because I definitely will do this if I ever find a live source of it, but I was interested in a food for sponges and thats why I changed the subject title.

It depends -- Sponges do capture some small phytoplankton (such as Nannochloropsis), but are unable to capture large phytoplankton (such as the size range of Spirulina or the ESV spray-dried stuff). Sponges pump a lot of water -- for example, an individual Leucandria 10 cm long and about the diameter of a pencil pumps 22.5 liters (about 5.5 gallons) of water through it's body every day. This volume is even more amazing when you realize that the cells responsible for pumping this water (choanocytes) are about the size of our white blood cells Aggregations of several hundred of these cells form chambers, and these choanocyte chambers may be as dense as 18,000 per cubic millimeter in complex sponges. Each cell has a tiny hair (flagellum) surrounded by a collar made of other even smaller hairs (microvilli). The flagellum waves back and forth from base to tip, pushing water ahead of them as they do. Each cell beats at it's own pace, and pulls water from very tiny openings (ostia) all over the surface of the sponge (the largest of which are about 1/10th of a millimeter) into the sponge, along the cell body, through the collar which captures food particles from 0.1-1.5 microns (that's about the size of an average bacterium), and pushes the water away from itself towards a common exhaust system (the oscula). As water moves along the cell body, oxygen diffuses into the cell, while carbon dioxide and other wastes diffuse out of the cell into the `exhaled' water. Some free cells (ameobocytes) cruise around through these water channels and ingest small algal cells, protozoans, detritus and other organic particles in the range of 2-5 microns (about the size of Nannochloropsis). Other freely moving cells (archeocytes) take these captured particles and complete the digestion of them before passing nutrients along to the rest of the body. Despite the ability to capture particles, however, dissolved organic matter (DOM) is *extremely* important to the nutrition of sponges; studies on three species of Jamaican sponges showed that 80% of organic matter taken up by sponges was below the resolvability of microscopy, while the other 20% was comprised primarily of bacteria and dinoflagellates. Only a very small percentage of the diet of sponges is made up of phytoplankton, and in many cases, the addition of live phytoplankton to culture systems with sponges actually *decreases* growth because the phytoplankton take up some DOM prior to being ingested and end up competing with the sponges rather than feeding them....

Posted to Reefkeepers emailing list, Thursday 7th October 1999.

There is a lot of diversity among the sponges, and like any other group (such as cnidarians, echinoderms or fishes) you can't make generalizations based on one that will ever apply to all of them Asking about an "orange sponge" is sorta like asking about an "orange fish," you're not going to get much useful information... In fact, it's even worse with sponges -- at least all fish eat something and it's just a matter of finding out what that is and providing it. The same cannot be said of sponges -- some sponges feed exclusively, many get most of their energy from the uptake of dissolved organics, and others are obligately photosynthetic and are primary producers more similar to an alga than another animal in tank care requirements. There is an article on sponges and how they work at http//www.aquarium.net/1196/1196_7.shtml if you want a lot more info about sponge biology and a couple of the considerations for keeping them healthy...

Thank you for your suggestions. Actually what my sponges have is similar to what you´re describing. It also started to happen when I moved to a new place and all at once.

Sponges take advantage of water currents (as described in that article), and any time they are moved or the current patterns in the aquarium are changed, there is a risk of negatively affecting the sponge.

I will also follow somebody else´s suggestion and place the sponges on the shadow.

Depending on the sponge species and it's requirements, placing a sponge into shadow may be all it takes to finish it off. If there is algae growing over the surface of the sponge, it is not healthy, and some sponges do not care about light regimes (although none should "require" shade, they often do better when shade tips the balance of competition against the algae, especially in nutrient-rich tanks), but some sponges require lighting even more desperately than do corals. It's really hard to predict the effect of shading without knowing anything about the animal....

I've been feeding DT & ESV since April so it shouldn't be starving.

Personally, I think starvation is the most likely explanation -- Why do you figure that adding these products prevent starvation in a sponge? Although sponges should (in theory) be able to eat particles of the size of Nannochloropsis (DTs), they are found to gain only about 5% of their total energy requirement from the filtration of particles this large (~3-5 microns). These animals have amazing abilities to withstand the effects of starvation, but even they have limits, and the added stress of moving the animal was likely all it took to finish it off...

I contacted Inland Aquatics on Monday and talked to Gary. He offered some suggestions that it might be a lack of silica in the water. I have plenty of diatoms growing on the glass so I don't think its that. He also suggested that I feed it some "beta-meal". He thinks a lack of beta-carotene could cause it to lose its orange. But to me, the white is not a fade in color, it looks like it died off.

I'm not very familiar with Beta-meal, but I would guess that it is simply dried Schizochytrium, and these particles (even if they didn't clump due to the drying process) are *far* too large for any sponge studied to date to be capable of eating (>50 microns, about 10 times the upper size limit for sponges). Adding the stuff may have a stimulatory effect, but similar to the SprayDried plankton from ESV, I would hypothesize that the growth of sponges is due to increased organics and bacterial growth from the decomposition of the dried algae rather than from the sponges eating it (which appears impossible from what we know of sponge biology). Of course the addition ought to increase (again in theory) the total availability of dissolved organics in the aquarium (like the other products), and that may be all the sponge needs if it is close to breaking even on either photosynthesis with symbionts or feeding in the aquarium already... Of course given that you're already adding similar products I cannot imagine why adding another would make any difference.

I recently started with adding Nannochloropis & Tetraselmis pastes and direct target feeding the sponge to see if it can be reveresed. Nothing yet.

Again, even for sponges that feed entirely by filtering (and photosynthesis does not come into the equation to make things more confusing) unless the sponge is very close to breaking even already, the additional 5% provided by their ability to capture these cells is unlikely to make much difference. If you don't know anything about the requirements or the biology of the animal, once a sponge starts to decline, it is almost impossible to reverse it -- after all if you don't know what's causing the problem, how do you "fix" it?

I discussed options with Gary such as cutting up the sponge like you would if it was a coral. He felt a healthy sponge would survive, but would not try it on a dying sponge unless nothing else was left to try.

I agree with this, unless as Kory pointed out, you removed the sponge from the water in transport. If so, then the degradation of the animal may be due to gas necrosis as the tissue exposed to air dies, produces gas and further kills adjacent tissue -- this is a common event, and one that is easily prevented. If the sponge has been exposed to air, and there is necrotic tissue, you will have to slice away all of the affected tissue to have any chance that the animal will survive.

I have also noticed that mushroom anemones will kill off parts of my sponges. Direct contact is not needed. Just being close and downstream will do it. Keep an eye out for that.

This is true -- many reef organisms participate in chemical warfare, although it is generally the soft corals and the sponges that are the most active in this respect. Anything that was moved close to the sponge in the re-arrangement of the tank ought to be suspect, and replicating the flow conditions and position of the sponge where it was originally doing well may be the key to helping it pull through....

Check out that article, see if you can figure out what has changed, and what the root of the problem may be. If possible try to recreate the habitat and conditions in which it was doing well as closely as you possibly can....