More Information, Answering Questions About Eggs and Size

Originally posted in 2006

Updated in 2025

This first picture shows an adult Berghia laying an egg strand, sometimes referred to as a ribbon when speaking about nudibranchs. Typically they are laid in a coil or concentric rings and can be laid on the face of a dime with room to spare. Berghia will lay eggs every 2 to 3 days when they are young and as long as there is a supply of food for them to eat. The young adults will consume many Aiptasia and mate often in the course of laying eggs.

Juveniles (“Pre-Adults 1/4 to 1/2 inch” or “subadult”) can begin to develop eggs at around 28 days old. At six weeks they can be in the size range from 9 mm to 12 mm on average, occasionally more or less. When they reach sexual maturity, then nearly all of the eggs in each strand will be fertile.

Old reference material reported that egg strands had 2 kinds of eggs; 1/2 the eggs were reported as motile and dispersed through the water column and 1/2 the eggs were reported to hatch and settle directly to non-swimming larva where they are laid. This is a research or laboratory error from combining several species of nudibranchs as if they were all one species. In the egg strands of our Berghia, 100% of the developing eggs are veliger and always hatch into free-swimming veliger larvae stage.

Originally published as reef-friendly Berghia stephanieae, these are now recognized as a distinctly different nudibranch from this Mediterranean species. This common name will remain for the aquarium industry but the correct scientific identification for our reef-safe nudibranch is Aeolidiella stephanieae (RE: 2005 new taxonomical record).

There are video files attached to the pictures below. Read the picture captions and paragraph to understand the videos and then click on the picture of the Berghia eggs to view their activity or the second picture of the larval Berghia to watch the two in the middle attack and start ingesting part of the Aiptasia. Observe very closely to see the golden-brown algae and Aiptasia cells beginning to flow into the larval sea slugs.

Berghia provide the proven method to contain and destroy all of the Aiptasia’s Planula Larva, Basal Cells and every piece of this pest anemone. The videos are .VID files using a Microsoft-1 Compression and should be easily viewed on most computers using Internet Explorer. This first is a 0.4 Meg video file, high-speed internet download in just a few seconds, the second is a 6.8 Meg video, download time about 40 seconds. Increase or decrease the size to optimize the focus for your monitor.

All of our adult Berghia lay completely fertile eggs that produce hundreds of healthy, viable larvae exactly like these pictured. We have a very well-controlled, strict selective breeding program here at INSTAR and our Berghia are inspected to ensure and verify they are in perfect health. These young newly metamorphosed larvae (below) attack a whole Aiptasia anemone and the anemone actually started to disappear while we were taking these pictures.

Even though they are already approximately 600 microns long, a little over 0.5 millimeters, they remain invisible because light passes easily right through them and through their internal organs as well. The pigmented cells they harvest from the Aiptasia help to hide their digestive system and blend it with the natural colors of rocks in the reef aquarium. Fourteen Berghia larvae are visible or partly visible and already exhibiting their natural colonial habit of working together to remove Aiptasia.

Even though our juveniles can take out a whole Aiptasia, we do NOT recommend shipping juveniles. When Berghia are shipped at the 1/4 to 1/2-inch juvenile size—even though they have the word “adult” attached to their description—this size is NOT an adult nudibranch. Juvenile membranes are very fragile and, if they are shipped, then they need special attention and time in a small tank dedicated just to them. Juveniles should not be placed directly into the reef under normal conditions. Juveniles also are not producing primarily fertile eggs and this opens the door for infection if they are shipped at this stage. This is a common mistake when lured into purchasing inexpensive nudibranchs from auction sites.

It makes a difference for your reef and success with Berghia. Many Berghia have a posterior filament some will refer to as a tail, and including this in their size measure will falsely describe the nudibranch and make it sound like it is larger than it really is. Proper taxonomical descriptions do not indicate including the posterior filament to inflate the size. We do not include this in our description or our measurement and we also do not include the oral antennae.

Our nudibranch size measurements are the actual body size to correctly describe Adult size. Shipping size is critical and it DOES make a difference to your reef. We use millimeters because the metric scale provides a more precise measurement for a smaller type of animal. Our highly specialized breeding program ensures our nudibranchs are ready to perform in your reef and they are regularly inspected. Even their eggs are inspected to be sure of fertility ratios.

This means we here at INSTAR can provide you with the best nudibranchs possible.

The pictures below show the Berghia sizes and help you to understand a little more of these tiny Aiptasia killers. Unlike something from a bottle that you can only use once, these will continue to kill Aiptasia. Berghia will NOT add any TDS to your tank water or cause Aiptasia to spawn—as many discover using bottled chemicals or injecting Aiptasia in an attempt to destroy them. Berghia also get into those hard-to-get, hard-to-see places!

These two pictures are of Berghia that hatched from their egg coils just 6 weeks ago. You can see by the measuring stick they are already 10 to 11 millimeters long. In the second picture of the undersides of the trio you can see the white egg mass even at this early age. The center one has a visible white egg mass in the posterior half of its body and so does the one on the left. The one on the right has a slightly translucent body and you can see through it to the base of the brown-colored cerata.

Berghia verrucicornis Nudibranch (Since 2005: Aeolidiella berghia stephanieae), Best Aiptasia Control

These are your hunters and we make every effort to sell them at or over 12 mm in length. This measure for our Berghia is their body length and excludes the tail and appendages. Their length is a variable state depending on their activity. At times they will expel water or curl up to rest. Once they average 12 mm or longer while hunting, a little over 6 to 8 weeks, this is when we offer them. We do offer smaller, younger ones on one of the specials and the ones we give for free are normally smaller.

A matter of good practice is that “Pre-Adults,” the 1/4 inch juveniles, are not desired for shipping as Aiptasia control except in a very few specialized applications. As the picture below shows, even our baby Berghia go after the whole Aiptasia. Our young egg-bearing adult 1/2 inch Berghia are still very thin-bodied and will grow considerably to well over 12 mm in the first month in your tank. They attack and eat Aiptasia and are very effective, very active at this age and size. We could compare them to the human teenage years at this size and everyone knows how much teens can eat!

Someone once said that only adult Berghia are effective and with our selective breeding, our young adult Berghia are very effective in removing Aiptasia. Young adult Berghia ship easily, acclimate easily and should do well for you in your tank. Just follow the instructions on the Acclimation Page of this site and handle gently, taking your time with all of the Berghia you purchase.

These are young adult Berghia, they are breeding and often will be carrying fertile eggs to be laid in your tank. They are not full grown yet. Adult full-grown Berghia can develop bodies that are over 30 mm long (1 & 1/4 inches) plus their threadlike tail that helps them handle swift currents and stay attached to the rocks. Adult Berghia of the correct species are not 2 inches long. It takes quite a number of Aiptasia to develop them to their full adult size. We think they should eat your Aiptasia and earn their keep. They are very active at this early adult age and consume many Aiptasia while laying thousands of eggs and growing larger in your system.

Depending on the resolution your computer monitor is set at, the above pictures are enlarged approximately 3x for easier viewing.
(This is a METRIC UNIT of measure in millimeters, NOT inches.) Unique Berghia Pictures Below.

Berghia verrucicornis Nudibranch (Since 2005: Aeolidiella berghia stephanieae), Jr SWAT Team On Patrol In The Reef!
Baby Berghia, The Jr Aiptasia SWAT Team On Patrol In The Reef!

This extremely rare photo from in the reef environment is the result of our Adult Berghia successfully breeding in the reef. Witnessing this event is so uncommon that such a group of baby Berghia have not been photographed like this until now. A few are easy to see but most of them are inside the caves. Look extremely close to see the 2 and 3 millimeter babies deep in the shadows, down in the rock cleaning the Aiptasia that have gone unnoticed out of the holes in the rock. The caves in the top center of this picture are lined with Berghia and are just barely visible after looking very close at the picture for a minute. We could not see all of them until the picture was enlarged. When the Berghia have cleared this area, they will move on to clear the rest of this rock. This will help the reef keeper to provide a perfect environment for growing corals and young fish. Baby Berghia cannot be shipped with good results because their tissues are far too thin and fragile at this age. Hazards of the reef await them as they migrate so they stay secluded and may never be seen by the reef keeper. (magnified x8)

Berghia verrucicornis Nudibranch (Since 2005: Aeolidiella berghia stephanieae), Jr SWAT Team On Mission Aipstinguish In The Reef!
Jr. Berghia SWAT Team, One Night In The Reef. Mission: Aipstinguish!

Another extremely rare photo; This one from in the reef at night while the reef keeper is sleeping. They are now about 5 millimeters and graduated to taking out larger pest Aiptasia. These events are never seen deep in the rocks where the Aiptasia originated. At least 8 of our Baby Berghia, Jr Aiptasia SWAT team have attacked the tentacles and oral disk of this larger Aiptasia and two more are closing in to help out. Looks like Berghia do really eat Aiptasia after all. It took 9 months to get to this point in this reef but the Berghia will prevail in the end. Pleasant dreams to the coral reef keeper.

The symbol we recognize as Yin Yang is actually the Chinese symbol “Yin Yang”. It represents the ancient Chinese understanding of how things work. The outer circle represents “everything”, the dark and light shapes within the circle represent the interaction of two energies, called “yin” (black) and “yang” (white), that cause everything to happen. The shapes are not completely dark or light, just as things in life are not completely black or white. The Yin Yang symbol has become known for balance in judgements. On a larger scope, all life seems to be a balance, there is good and bad, give and take in everything God created.

Our Berghia nudibranchs take out Aiptasia pallida (Atlantic Caribbean Aiptasia sp.), Aiptasia pulchella (Tropical Pacific Aiptasia sp.) and other Aiptasia sp. giving new hope and new life to your reef! It is well documented in scientific literature that these Berghia stephanieae nudibranchs are specific target predators, never bothering anything else in your reef, only seeking to kill Aiptasia in tireless effort to balance the living ecosystem, controlling the pest Aiptasia anemone.