Back in 2005, I received a bucket full of Montipora coral, but soon after adding all of those to a temporary frag tank, I discovered the coral infested with tiny pests. I decided I needed to try to pluck off a few and quickly realized how hard they were to remove with forceps. Maybe some very sharp tweezers would do the trick. I saw eggs too. UGH!
Anyway, you know I love to take a picture of this stuff, so here are 17 images for your edification. The nudibranchs were put into a tiny sampler jelly jar, which was then placed on top of a regular jelly jar (Bon Maman is the brand if that helps give you a sense of scale) and put one of the 5100K refugium bulbs next to the jars for some lighting. Now that you see the size of the 'studio', I do hope this helps you realize how small these are.
That is the tip of my index finger on the side of the glass, again for a sense of scale. These are parents, and the offspring are mere dots by comparison.
These pests tend to lay their eggs on the underside of the coral, right at the margin of new living tissue. When the egg casings open up and the new ones crawl out, their immediate desire to eat is satisfied by the living coral, and as they eat they grow. The parents move into the coral to feed, and areas they clear are soon used to lay more eggs. The eggs are white dots, like microscopic bits of rice.
When inspecting the coral, you may see what look like off-white hairs standing up off the surface in a tight nook. Look closely, using a turkey baster to flood the area with water to see how their fronds move as the torso stays in place. That is how you'll know for sure what you are looking at, and that it isn't calcium-based growth or similar. A magnifying glass may help, or macro pictures that are blown up on a large monitor for easier verification.
The more I looked, the more I found. Argh. I saw a couple on the acrylic, under a coral. Using forceps, I tried to pluck them off and put them in the jar, and discovered little white eggs there too! Great, they were happily breeding.
The good news was this occured in a frag tank and I could basically toss out everything and start anew, but I wanted to destroy these pests and keep the frags growing.
Once I knew what to look for, they were easier to spot, allowing me to inspect the corals closely before moving any to my reef. I siphoned out about 50 or more daily, and took more pictures. However, I saw lots of eggs and those didn't siphon off.
Anywhere I saw two of them together, I found eggs. That was surprising, as I would have figured they'd lay eggs individually rather than needing a mate to breed. Maybe it was coincidence, but that is what I observed.
While a variety of dip solutions were employed, and a number of wrasses were recommended for pest control, in the end it was safer to toss out the infected corals than risk my reef. Always inspect your corals closely to avoid damage to the display tank.