High overnight mortality rate???

[fragman2]

I have bred and raised several varieties of clownfish for several years. The problem that I’m having for the past year or so is a low survival rate for newly hatched out fry. I would love some advise as I try to figure this out.

On the expected hatch out night I transfer a tile or flower pot to a rearing tank a couple of hours before “lights out”. I have used 3 gallon, 5 gallon and 10 gallon tanks with 5 or 6 inches of water and two air stones. I’ve experimented with both small and medium sized bubbles by using different air stones In an effort to get the perfect balance of aeration vs turbulence. I usually get a 90% to 100% hatch out. The problem is that in the morning after hatching I have a between 70% and 90% of the fry dead on the bottom of the tank. I’m able to raise the survivors with what I would consider an acceptable mortality rate. I add rotifers and tint the water in the morning after I siphon out the dead ones On day one. The parents are fed a variety of foods including flakes, pellets, LRS Fertility Freenzy, brine shrimp, mysis, and fish roe etc... the temperature ranges between 80 and 81 degrees.

Any ideas of how I might get back to a more normal overnight survival rate?

 

[mfinn]

Do you think they get trapped in the corners of the square tank and suffocate?
Are there any of those curved bottom tanks still around?

 

[fragman2]

I don’t think that is the case as the dead bodies are scattered everywhere. They look fine right after hatching, then 6 or 8 hours later most are dead. I suspect that I have weak fry or a “dangerous” rearing tank. I have tried to address both of those possibilities without seeing any improvement.

 

[Lasse]

Is it the same breading pairs and how old are they?

Sincerely Lasse

 

[ThRoewer]

The going to the bottom (and sides) is due to light reflecting in the glass and the larvae becoming disoriented.
Dimming light source and adding green water to reduce visibility helps to some degree. Flow patterns are important as well and it is nearly impossible to get those right in a rectangular tank.

If your larvae die soon after hatch it may also be that the parents are not producing good eggs. Parent feeding may be one cause aside from poor genetics.

As for age of the parents - I had an ocellaris pair for 20 years and they spawned for most of that time regularly until a stuck heater killed them. Even at 20 years old their fry was still strong and survived.