Why take them out?
Here is a good read on sponges,
http://www.advancedaquarist.com/issues/april2004/invert.htm
I had a very similiar or maybe the same type as you pictured there many years ago. I started thinking it was a problem and pulled it out where I could but it would grow out from the rock lieke crazy. I posted on line and found out the sponge was nothing to worry about, and as my tank matured and I started running it cleaner the sponge growth went away. I love sponges in my tank they are a good thing not a bad thing. My angel eats any in sight now though.
From the article
"The aquiferous system is just as amazing: 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. The impressive sieving capacity of even a relatively small sponge is what has led some to champion their use as natural filters for reef aquaria (Tyree 2003). There is no doubt that sponges can filter a surprising amount of water through their bodies on a daily basis. This pumping capacity is even more amazing when you realize that the cells responsible for moving 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 μm (that's less than 1/600th of a millimeter -- about the size of a 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 μm. 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. Dissolved organic matter (DOM) is extremely important to the nutrition of many sponges; for example, 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 comparised primarily of bacteria and dinoflagellates (H.M. Reiswig, unpublished data, from (Reiswig 1975)."
I think the sponge you posted does depend fully on this feeding and with less detritus, and food in the tank for them they will not be an issue.
JMO