Centropyge eggs not developing.

I keep a pair of lemmonpeels (C.flavissimus) and a pair of flames (C.loriculus).Each pair is housed in a 130 x 40 x 40 cm runway tanks,where the water comes at one end,at surface level,and exits at the other end.Both pairs spawn every night and eggs are collected in a 400 mic screen at the end of the outlet hose.After collection,the eggs sink and none of them shows any development.
Trying to understand what is going on here,I considered the following factors:
 
The two males are sterile (unlikely) or became so due to some WQ or nutritional issues.
Hypothetical,and hard to find how to improve.Recentlly a hobbyst reported that placing a "moon light" brought fertility to his fish.Simple as it was,I did it,but didn´t work.
 
The shallow tanks don´t allow a successful spawning rise.
Most probable,but seeting a system of "pelagic spawning drums"looks too much complicated and I must be sure before I undertake it.
 
The harsh treatment received during collection harm the eggs making them sink and non viable.
It is accepted that fertile eggs float and bad ones sink.But the eggs of my fish must have floated,otherwise they wouldn´t get collected in the surface outlet.
 
Any suggestions will be welcome

If it was me I would try and disprove all factors to determine route cause.
I would start with the turbidity issue. Could you collect some eggs manually (if they spawn every night) you could then rule this out as a factor if the eggs prove to be fertile and float.  If they do not float and are infertile, you could then look at other factors. Diet, sterility etc.

Do you see fertilization at least? You should see it as an imperfection in the sphere on the outside of the egg. Here's a photo:
 

 
What I'm talking about is the little puckered place to the left and a little below the oil droplet (the large, black, out-of-focus area). I believe that's where the sperm entered the egg.

--Andy, the bucket man.
"Not to know the mandolin is to argue oneself unknown...." --Clara Lanza, 1886

I think you'd also notice the first cell division fairly quickly if they're fertile...

'Tis true. That is the first obvious question: Do you see cell division? If yes, some environmental factor is killing the embryos. If not, do you see the sperm attachment? If yes, there's a problem with the eggs. If not, the male's shooting blanks or fertilization isn't happening for some other reason.

--Andy, the bucket man.
"Not to know the mandolin is to argue oneself unknown...." --Clara Lanza, 1886

Thanks guys!
Never done that,but I could shut all water circulation before spawning and then scoop the eggs from the surface with a net.I think martin M.did that.
And I had another dumb but easy to work idea inspired in the FW hobby.Betta splendens´eggs don´t develope if they fall to the bottom,but it is said that they can be saved by placing them in very shallow water,just enough to cover them.
I am checking the eggs under a dissection scope,but fertile eggs should be embryonated by noon of the next day.

 
If not much, much earlier. My wrasses are usually at blastula within 3 to 4 hours I think.

--Andy, the bucket man.
"Not to know the mandolin is to argue oneself unknown...." --Clara Lanza, 1886

What I look for (with my dissecting scope) is gross modifications,ie.the embryo long as the egg diameter.I wanted to find pics from my old library at RC but can´t access now.Nor I can link to my old threads there.
Forgot to mention,and I don´t know if it is relevant,but these two males were former spawning females that became widows and were then mated to smaller fish.

You ought to at least be able to see the first couple of cell divisions easily. I just took this picture with a regular camera with a macro lens and backlighting, but I can see them easily with just a magnifying glass.
 

 
How long ago were the males females? They might be firing blanks as their internal plumbing switches over.

--Andy, the bucket man.
"Not to know the mandolin is to argue oneself unknown...." --Clara Lanza, 1886

 
There is an article (can't find it now) where they speculated that centropyge spawning rise height, and fertilization, was at least partially effected by water surface smoothness. The reasoning was, when the surface was smooth the fish became spooked by their own reflection, ending spawning prematurely. When the surface was agitated, spawning proceeded normally with high fertilization success. From memory, this was tested to approx. 450mm tank height.
 
Chris

Awesome pics,Andy!How far did your wrasses go?Still working with them?.
They changed sex years ago.I guess that some few eggs could develope,even if the tanks are shallow.Matt P.could obtain good eggs in a small tank,even if C.argi are smaller fish.
Thus I fear that if I move them to spawning drums,things could remain that bad.

I don't believe any of the wrasses have made it to full larvae. They keep dying off on me as prolarvae. Still working, though it's mostly been about trying to get good at culturing possible foods.
 
How old are the new females? I recall now that the juvenile I added to the sixline male spawned poorly for a couple of months before her eggs started looking really good.

--Andy, the bucket man.
"Not to know the mandolin is to argue oneself unknown...." --Clara Lanza, 1886

Problem solved!
It´s nice to see how we can help each other in these "think tank" boards.
 

Trying this was simple enough (simpler than setting spawning drums),so I set a fine mesh net across the main flow and collected some eggs.First thing I noticed was that they all floated!.Few hours later,development was evident in 4 out of 7 eggs checked under a compound scope.(Dissect scopes are not good for this.)
And 12 hrs after spawning, embryos were evident:

 
So it was not the shallow tank that prevented fertilization.That could be a sort of myth.Matt P.had excelllent fert. rates with C.argi and mandarins in his 35cm tall cube.I spawned mandarines and had reidi SH breed in a 10 gal.
The problem was the traumatic high turbulence collecting method,that affected both egg´s buoyancy and viability.This must be considered when collecting techniques for pelagic eggs are devised.

It's good to hear that you are getting closer. Maybe we can get Chad V. to design a Egg Collector to go along with his larval snagger!

Chad Penney - MBI Council
Agis quod Adis

Excellent results! 

http://www.fishtalpropagations.com/#!home/mainPage
"Making captive breeding easier."

Nice. There be an embryo. I've certainly had successful mandarin spawns in 2 feet of water that got nowhere near the top. For that matter, the sixlines never go anywhere near the top of the water column, either, though they are in 4 feet of water.

--Andy, the bucket man.
"Not to know the mandolin is to argue oneself unknown...." --Clara Lanza, 1886

Glad you worked things out I'm chuffed for you.
 
Sorry pleased. Just realised you probably would'nt understand "chuffed", would you?

I certainly won´t.But went to the dictionary and it comes to mean both pleased and displeased in "british informal".Oh Brits!

We normally say Chuffing when displeased........Hahahaha. Perhaps I should use more of our more unusual dialect and words for you guys the other side of the pond? You can all get your dictionarys out.

So the final conclusion is that pelagic eggs (at least these eggs) are harmed by sheer turbulence and we must collect them with TLC
By following this guideline,I can now collect large numbers of eggs and fertility rate is almost 100% of the floating eggs.
So we can now move to the following step;incubating the eggs and the prolarvae until they become feeding larvae which we can try to rear.This will be covered in: http://www.mbisite.org/Forums/tm.aspx?high=&m=52332&mpage=1#52468

This is great information Luis! Thanks for sharing your journey with us. As pelagic spawners are a line that most of us have yet to cross I'm sure this will be a very important lesson that many of us will need to keep in mind.

Chad Penney - MBI Council
Agis quod Adis

This is great info. What I'm curious about is how they survive in the wild if they are so fragile... any thoughts?

http://www.fishtalpropagations.com/#!home/mainPage
"Making captive breeding easier."

In the wild they don't bang into walls nearly as much.

--Andy, the bucket man.
"Not to know the mandolin is to argue oneself unknown...." --Clara Lanza, 1886

Actually,the plankton isn´t disturbed with the typical offshore wave action;they move with the water.

Thanks Chad!.Indeed there´s a lot of fish species waiting there that we start to work with them.
Not considering surgeons and butterflies,which are a bit large for the typical hobbyist tank,after small angels we have many very nice labrid species.Kate and Andy here are spawning them.
And then we have hawks,anthias,and more...