Kathy, just got your email - will respond shortly - thanks.
The big news, I think we had the best hatch yet on this most recent spawn. Everywhere I point the flashlight I see larvae...it's not uncommon to have 3 or 4 in the beam at any given point! MAYBE....
Tonight I'll try to do a headcount once the lights are out (a bit easier to spot the larvae in my rotifer soup!). I'm pretty pleased with the results of this hatch.
It's also worth mentioning that a couple hours ago I added in the last of my freshly mixed saltwater (Dr. Foster's sent the wrong salt this time around, so I have to SEND IT BACK and then they'll ship the right salt...looks like I'm headed to the LFS tomorrow!). I also added 2 basters of the "Mandarin Mix" (50% T-Iso, 50% Tet.).
To recap this somewhat successful incubation method:
Incubation Vessel - 10 gallon tank, filled most of the way, with one relatively strong air feed coming from the base of the tank at a rate of several bubbles per second.
Incubation Water - I've tried sterile, freshly mixed, and "used", and in the end I don't think it's made that great of a difference.
Broodstock Diet - The only change that's been made in the last 1-2 weeks is that I've started added Reef Plus to the soaking regiment.
Temperature - the broodstock and 10 gallon are both right around 78F steady at this time of year (during March/April the broodstock tank usually ran closer to 75-76).
Collection Method - using a pipette with the end "sawed off" to make for a larger opening, I'm able to suck out most all of the eggs while collecting an extremely minimal amount of the parent's tank water. I'm also getting less "GUNK".
That pretty much describes how I've done the last 3 "successful" batches. Something in there is obviously KEY to helping get better hatch rates vs. all the other 1 or 2 or 5 or 7 larvae that most of the other, earlier methods I've tried have produced. Perhaps down the line I'll try splitting up more cultures and doing more formal "experiments" to make a definite test of what works, what doesn't, what has an influence on hatching success and what doesn't.
So there's maybe 3 dozen larvae or more in the 10 gallon tank along with SS rotifers and Nannochloropis, Tetraselmis and T-Iso. The NEXT thing I'm going to change on this batch is that I'm going to keep a light on 24 hours.
My REASONING behind this 24 hour lighting is that while watching our lost "lone larvae" in the morning he'd be skinny and in the evening he'd be FAT. So *maybe* we can get better larval survival if they have SOME light to feed with at all hours of the day.
I may also go back to seiving my L-Strain / Copepod cultures to get some variety of diet into the mix...that can't hurt either!
I'm off to do a water test on the larval tank just to see where things are at.
MP