So, you have your first "clutch" of clownfish eggs... now what?
If you were lucky enough see the spawning event you can estimate when they will hatch. Depending upon species, the eggs should hatch between day 6 and 10 after the spawning event, usually not long after lights out. The most common species, A. ocellaris and A. percula will hatch in 7-8 days.
Newly spawned eggs will usually be bright yellow, orange or red. Over the next several days the eggs will darken and then appear "silver" around day 7 or 8. The "silver" is actually the eyes of the larvae reflecting light. This is a good indication that they are close to hatching.
During the afternoon before they are expected to hatch, move the clay pot, or ceramic tile, to a stand alone 10gallon tank that has been filled with about 6 gallons of water from the broodstock system. This tank should be kept at the same temperature as the broodstock system.
Here is what the eggs look like at the moment I transfer the pot to the hatch tank. (Note that the tiny eyes are visible in each egg.)
A small clutch of Picasso eggs on a ceramic tile during transfer.
Place an airstone inside the pot or underneath the tile to aerate the eggs with a gentle flow of bubbles. This takes a bit of tweaking... too slow and the eggs will succumb to fungus, too fast and the eggs will get bounced around too much. Now just sit back and wait for the eggs to hatch.
Ceramic Tile Method
Morning After Hatch (1 DPH)
The next morning I add enough IA to tint the water green. Next I harvest rotifers from the culture vessel and add them to the hatch tank. This is know as the "Greenwater" method. Getting the density of phytoplankton right is more of an art. You want it green enough so that you can't see the bottom of the tank, but not too dense. The same goes for rotifer density. In short, you want enough rotifers so that each larvae has plenty to eat and not waste too much energy searching for food. Rotifers will look like dust in the water.
It is possible that all of the eggs won't hatch at once, in this case I leave the tile/pot in the tank for another night for the rest of them to hatch.
After all eggs have hatched, remove the pot and increase the airflow slightly.
Don't forget to add top off water to make up for evaporation.
Notes about Greenwater: The basic premise of the greenwater method is two fold. Phytoplankton provides a food source for the oganisms that the larval fish will be eating. Tinting the water with the phytoplankton also provides visual contrast for the larvae to find the food oganisms. If the water is too clear the larvae have a hard time finding their prey. In this instance the larvae will expend too much energy going after food items that are too far away.
As mentioned above, the exact amount of phytoplankton to use will depend on the rearing vessel and the rotifer density. In general you don't want to be able to see the bottom. As the rotifers feed on the phytoplankton the water will begin to clear. If the larvae start to gather at the sides of the tank more phytoplankton should be added.
Days 8-20 (8-21 DPH)
Around day 14 I start to siphon detritus off the bottom of the tank each day. Being carful not to siphon the larvae. On average I will siphon out about 1/2 gallon of water and replace it with 1 gallon of water from the broodstock system. This will gradually increase the water volume in the tank as well as provide clean water. At this point I also add a sponge filter to replace the airstone and I stop adding phytoplankton. The water will clear up in a few days.
Between days 7 and 9 most larvae will undergo metamorphosis and become juveniles. They will start to look like miniature clownfish.
Days 21-28 (21-28 DPH)
At this point you should have a tank full of happy juveniles. Depending on species (more on this later), I usually transfer them to a grow-out tank around day 28. Transfer only a few at a time to be sure that they are ready. If you notice any problems, wait another day and transfer a few more.
It is important to try to have the water in the grow-out tank be as close in temperature and salinity to the hatching tank as possible. I keep my broodstock, hatch and grow-out systems at about 82F with a salinity of 1.020.
Hint: I have a plastic mesh screen around the drain pipes in my grow-out tanks, when my juveniles are too large to fit through the mesh I start transferring them. This isn't a scientific method but it seems to work for me. See below:
This plastic mesh is used for needlepoint and comes in various mesh sizes. You can find it at craft stores such as Michael's or Joann Fabrics. I use a larger sized mesh for the drain pipes in my broodstock tanks.
Species Differences & Hints
The guidelines above are for A. ocellaris. Different clownfish species will mature at different rates.
Black A. ocellaris grow significantly slower so the feeding and transfer schedule should be adjusted, adding about 4-5 days.
A. ocellaris will show their first stripe in just a few days with the middle and tail stripe to fill in during the second week.
A. percula, on the otherhand, stripe much slower. The head stripe shows up during the first week but the middle stripe is often still developing after 2 months. The tail stripe can take a year to fill in so don't be worried. They also grow slower than A. ocellaris for the first few weeks but they will catch up.
I've raised A. ocellaris and A. percula that were born within a day, or two, of each other. That is when I noticed the differences I pointed out above.
Hint: Dealing With Dominatrix Issues
There will also be growth differences within each group of siblings. After a few weeks in the grow-out tank you'll notice that 1 individual will become dominant and take over half of the tank. Imagine having 200 juveniles in a tank... 199 will be on one side and the "dominatrix" will be on the other.
At this point I will isolate the dominant one by placing it in a breeder net inside the tank. Of course when you do this another one will take over the dominant role in a few days and will need to be isolated as well. When I get about 8 indivuduals in the breeder net I will move them into another grow-out tank. Around 2 months I end up with the juveniles in different tanks based upon size rather than age.
I also use this technique if I notice any runts that don't seem do be getting enough to eat. By isolating the smallest ones they get a chance to bulk up a bit before going back in with the others. This works quite well for me.