Very high Clownfish Larva mortality rate

[Jboy]

Hello,

I have a pair of Ocellaris clowns that have been a breeding pair for a few years now. In the past, I have been able to raise about 50 or so clowns per batch of eggs laid.
In my last three batches however, the 48 hour mortality rate from hatching has been extreme. I am losing over 90% of the larva (they do hatch) in the first day or so. Rotifers and larval tank conditions are the same as when the successful batches were being raised.
As such, the only thing I can think of is that it's something in the eggs themselves. Wilkerson's book offers no clues.

Could my breeding pair just be getting old? Any other ideas?

Thanks...

 

[David M]

Rotifers and larval tank conditions are the same as when the successful batches were being raised.

It's easy to overlook something that is in fact different. Your pair should be getting better, NOT worse, so it's more likely you than them cuasing the problem What about air level, as high as before? Have you changed salt/ water source? Temp is the same? Adult nutrition the same? Dig deep man, something has changed.

 

[Kathy55g]

It could be something as basic as the phytoplankton you feed the rotifers. Or the fertilizer you feed the phyto. Start fresh with that and see if things don't go better.

If your fertilzer is off, old, or contaminated the rotifers will not be nutritious enough to sustain the larvae. If your phyto is contaminated with a wrong strain or bacteria, that could throw them off. Recently mine have been contaminated with a wild green strain. The only reason I know that is my T Iso is growing green instead of brown!

If your culture water is contaminated with a wrong bacteria, that could be the culprit. If your larval tank is contaminated...

It is summer,and a lot of stuff is flying through the air!
Good luck, man,
K

 

[Dman]

If you're experiencing mortalities like that in only the last three batches then something has changed. Have you kept detailed notes you can fall back on? Something as simple as air pump placement can affect water quality in a big way. Poor nutrional quality of rotifers is probably not the suspect (sorry Kath, unless the rotifers are gut loading on something that's poisonous) as the fry should have enough in their sacs to last three days, unless the last few batches have been "thin". This would point to parent nutrition.
Typically mortalities like you've described are environmental such as poor water quality (pH, Dkh, NO2, NO3, Ammonia, etc.) , improper salinity, temperature fluctuations or low levels of O2 or they're bacterial in which an antibiotic can sometimes help.
Go back over your notes and re-test everything, somethings missing.

 

[Jboy]

Thanks guys,
Very good comments.
I am also thinking it's not the rotifers (although the source for them has changed from previous batches), because the losses have been happening in the first 24 hours. In fact, in the last batch, most of them were gone by the morning after the hatching.
As for water, I use water from the parents tank, and I have never had problems with it, although I have not been doing extensive testing. What do you guys use? Parent tank water, or new RO water?

The one thing I was thinking about, was the aeration. As per Wilkerson, on the night of hatching, I place the airstone below the eggs, and then turn on the air so the flow is quite strong. These past batches I have used a new pump for this, and I think the initial flow is greater than what I was using before. Perhaps that is the problem? How stong should the flow be once I place the eggs in the larval tank the night of hatching? Of course, the morning after hatching, I reduce the flow to produce slight surface motion.

The last thing is lighting. Again, because the losses are happening so quickly, I don't think this would be an issue. For the record, my larval tank is a 5 gallon, with 2x15watt bulbs for lighting. To dampen the lighting intially, I use folded paper towels between the lights and tank top.

So really, the possibilites are: Water, initial aeration, and lighting.

Thanks again.

 

[David M]

If you are going to use parent tank water try bleach sterilizing it first and see if that helps. I do this routinely, use sterilized system water diluted to 1.016 SG.

 

[Kathy55g]

I once killed a hatch with too much air beating on the eggs while they hatched, and perhaps rough handling of the eggs themselves.

Did the dead ones look bent? That's how mine looked.

 

[Jboy]

o.k,

Well I now have one fry left from my latest batch. It has to either be the air during hatching, or the water itself. I will reduce the airflow on the next batch.

As for the bleach sterilizing David mentioned, I do not know what this process entails. David, do you have a source of information which would tell me how I can do this?

Thanks
Jason

 

[David M]

My way (I'm sure there are others) : Clean and fill the tank. Fill it past where it will be with larvae in it. Set in place any airlines, heaters, pumps- what ever will be in there and turn on the air. Add household bleach one ml/ gallon and let it sit for 30 minutes or so. I cover the tank so little bleach bubbles don't go flying into the tank next door After 30/ 40 minutes use any standard de-chlorinator as directed ( I use Amquel and double the recommended dose). Remove some of the water, scrub the tile/ pot, whatever and add it to the tank, it will be fine. It scared me to death the first few times but I've been doing it for over a year now I suppose, no ill effects. I tried this at Edgar's suggestion because I was losing nests to fungas, that is now a thing of the past.

Another thought, one thing easily overlooked is the quality of the air getting pumped into tank. I once read about a hobbyist having repeated problems with his tank, turns out the air pump sat on the floor and he had a housekeeper. Yup, she mopped the floor with an ammoinia based cleanser, guess what the pump was breathing Placing the pump up on a shelf solved the problem.

 

[Kathy55g]

i put 5 gallons of saltwater in the tank to match the parent tank salinity, the heater, the airstone and line, the ammo alert badge, and add 5 ml of chlorox, just straight old fashioned chlorox, not the perfumed kind. I let the heater heat and the air bubbles bubble over night. Then I add 5 ml of sodium thiosulphate previously mixed at 60 grams per liter (6 grams per 100 ml). I test for chlorine, and then I am ready to add larvae.

This method is easy, and sterilizes everything.

 

[Jboy]

Interesting,

So you actually leave the chlorox in the water and let the Amquel take care of it? Wow, that would scare me to death!!! And David, when you say "scrub the tile/pot", you mean the tile the eggs are usually laid on correct? And Kathy, so you would be adding actually .3g of undilluted sodium thiosulphate, correct?

Great suggestions guys, I will certainly do this for my next batch. I will also change the airpump just in case

Thanks again.
J

 

[Kathy55g]

I don't use Amquel. The sodium thiosulphate inactivates the chlorine. I test for chlorine before I put anything living in it.

Now you are making me do math ......

5 ml of 6 grams per 100ml = 30/100 grams =0.3 g

Correct!:lol:

 

[Kathy55g]

but I dissolve it first before I add it just to make sure it gets to where it needs to go.