Sponge shrinking--Need more food?

[monicaswizzle]

About three weeks ago I added a ball sponge to my sump. The sump only gets moderate water flow, but the sponge is about four inches away from a powerhead that rotates, so it gets a very perceptable amount of alternating current. I feed the display tank three times a week with a mix of Marine Snow and Kent Marine Phytoplex. Since adding the sponge I haven't increased the amount per feeding, but I did go from two feedings to three per week and instead of adding all the food into a water stream in the display I add about 1/4 of it directly in front of the sump powerhead that is near the sponge.

When I got the sponge it was about 4 inches "tall", 4 inches "wide" in one direction and two inches wide in the other. All of those dimensions seem about the same, but between the "top" of the sponge and the base (the part that is wedged between two rocks and clearly had been connected to the reef), the sides are now looking somewhat concave. Before they were fairly straight so that the sponge stayed about 2" "wide" from top to bottom. Now it has a noticable "indent".

Is this a sign of starvation? Do you know if I should feed the tank more often (I just added some clams, so I was going to bump to 4 days per week anyway), or should I feed more per feeding (I am using about 3/4 of the recommended dosage per feeding, based on total volume display plus sump), or should I be feeding something entirely different and/or additional to the marine snow and phytoplex.

If you have experience feeding ball sponges (or other) for a fair while, I would love your advice!!

 

[T Man]

Sponges are difficult to keep, they are sold mostly for food rather than decoration or filtration. I have a rock that I purchased years ago, I did not know that a sponge was there until I removed all the rock to a different tank. It was under an overhang out of direct light, do you have a light on your sump? it is possible that you could have too much light on it. Also, has it ever been exposed to air? that can do it in slowly too. Hope this helps a little. TinMan

 

[monicaswizzle]

Thank you. Hasn't been exposed to air since I got it. It is from Drs F&S, and their quality is usually pretty high, so I doubt they did either.

The sump is 50 gallons and gets 50 watts of NO light. Enough to grow Cheto slowly, but not much at all in the marine world.

 

[GoingPostal]

I would switch to DTs phtyoplankton, I believe marine snow is mainly dosing nitrates and not all that useful to filter feeders.

 

[monicaswizzle]

Hmm... the folks at Drs Foster and Smith really push Marine Snow for filter feeders. And I read some article on RC that had tested various filter foods and found that Marine Snow was one of the few that actually had useful particle sizes for many filter feeders. That said, my clam and Feather Duster seemed to do fine (only 6 months or so trial) on the Marine Snow, but when I added a Sea Apple it didn't seem to be feeding regularly until I added in the Phytoplex. Which is why I now use a mix. I will look into DTs phytoplankton. I could always use a mix of all three.