When changing our filter sock, we always look inside to see if there is anything swimming around before replacing it. There is usually some copepods or amphipods, so we dump them back into the sump. The last sock change revealed something new, and no, it was not a Sharknose Goby.
What was in the sock were a dozen or so tiny red/purple “dots”. On closer inspection, we discovered they were moving. So we got out or microscope and captured a video of these little swimmers.
Having absolutely no idea what they were, we posted the video on MichiganReefers, a saltwater aquarium forum site, hoping for help to identify them.
Sea Squirts! These little hitchhikers must have come from the new live rock when we recently had our aquascape redone.
Sea Squirts are marine filter feeders. They have both male and female reproductive organs and spawn by releasing eggs and sperm into the water at the same time. Tadpole-like larvae (what you see in the above picture and video) develop from the eggs after 3 days. This motile stage helps to distribute them and only lasts for a short time before they settle and become stationary.
Looking a pictures of Sea Squirts, the possibilities of what they will look like or what color they will be seem endless. One thing is for sure, they are unusual and cool, and a great addition to our reef tank.