i suggest that you may reduce the level of water in the tank. If the level is too high, larvae will spend too much energy for keeping on water surface.

Hello - Unfed larvae die at ~13-14 dpf, after exhaustion of yolk sac. It is very reproducible, first larvae die ~10dpf and 100% are dead at ~15.

So I guess if you have larvae dying at 5 dpf, this is not a problem of food.

It could be a problem of water. We use 1X E3 medium as described in zfbook.

You could have trouble if you use inapropriate water, if you add too much salt along with artemia (must be rinsed extensively with freshwater), if pH is not stable, if O2 % drop below 3-40% the last two could be due to overfeeding which degrades water quality...

It could also be due to a temp

Our group feeds zf larvae after 5 dpf with powdered dry food (eg: Tetramin, NovoTom), until 3-4 weeks, then we add fresh artemia. I know that other groups use different supplements such as paramecia or spirulina. You can contact for more info the ZIRC centre, which is one of the main reference centers for zf maintenance.

You wrote : "I saw my seniors put some java moss into the larvae tank, after few days the tank become cloudy and lots of "dusty" mass start to form at the bottom of the tank. "

This really reinforce my opinion that your pb is water quality rather than food !

Many things can grow in dirty water and it is going worse with time. What you described could be mold. You should clean very well eggs, remove all chorions after hatching, and avoid introducing anything except food in dishes and you could add methylene blue to prevent "fungi" growth.

How frustrating. Sorry to hear about your difficulties. I would direct you http://zebrafish.org/zirc/documents/protocols.php and then the the "Nursery" section. Also, as Juliam comments water level and water flow should be low for these very young fish. Good luck.

Rearing larvae can be a very frustrating task until you get a working protocol. We use paramecia and artemia, with supplements of small particle dry food. That really helps when raising injected animals (such as those from transgenesis or talen mutagenesis) as those animals often have a swimming difficulty early on from the microinjection process.

Water quality is also paramount. We keep the water level initially low (in static tanks) to keep the food density high, then slowly add fresh water until the larvae are big enough to add regular flow to the tanks.

Hi Jiulin:

I never think about the water level, will try to reduce the water level tomorrow, hopes that the larvae can search for food easily, especially artemia.

Hi Xavier:

My senior told me that those "dusty" mass are infusoria growing inside. I picked up the mass and observed, I saw few infusoria inside the mass, so just curious that is this the correct way to introduce the infusoria? Feeding larvae with artemia at 4dpf, can the larvae consume it? Some books and info at internet says it is too early, because artemia is too big for them. You said that pellet can be fed to larave, what's the brand of your pellet? How frequent you change the water?

Thank you

It's easy to tell whether a larvae can eat artemia - just look for red-bellied fish! Few animals can eat artemia even at day 6; when a tank has most fish eating artemia, we reduce the amount of paramecia we feed.

Hi Stephen:

Yes, I found that most of my injected larvae are not active swimming and searching for food, even the artemia are in front if them. Seems that raising injected larvae is a tough task. So at when you start to feed them with artemia?

thank you

We use paramecia for injected larvae as it lets the food swim to the fish. We go ahead and start adding artemia about a week in, waiting for another week or so before switching over to artemia as the primary food source.

All what has been said above will help you to improve survival but, as I said above your problem is likely not related to starvation. I've attached a graph showing survival of larvae (from different exp.) which never received food. As you can see, larvae died days 12 and 14 with almost no death before this age (and I've dozens of such graph). Logically death occuring before this is not related to food deprivation.

My conclusion, is that you should first improve your breeding conditions water quality, temperature, cleanliness (remove all dirty things: feces, chorions, dead larvae and avoid to introduce them ;) )and so on.

Our pellets are sea bass Inicio+ 0.5 mm produced by Biomar (www.biomar.com)

As pointed out above using a combination of paramecium and powdered food for larvae usually works well. (This is the powder we use, a commercial stuff, found in most pet stores: http://www.herpsupplies.com/product.cfm?id=Sera-0720) We use this after 5 dpf, and post 10 dpf we start gradually adding artemia. Once you are reasonably sure that most larvae can catch artemia (after feeding you see their bellies becoming orange), you can gradually leave the original mix out.

That said, in my experience inbred strains sometimes can have very high mortality rates, regardless of the feeding regime.

How about liquid fry food? The pet store recommends it to me

Hello - We tried (just once so little experience with this) it dirties water very quickly, helps fungi to develop and it smells really bad... I'm not sure we ever finished the tube ;)

Hai Gan Jen Yang,

Very sorry for this late reply.

You separate egg white and dilute with water and feed them in little amount and see the difference.

I was also getting the same problem, But now its okay.

And after few day when you see the larva grown up then feed with egg's yellow part (boiled) in little amount. They will eat happily and its safe to digest... :) and growth rate is fantastic ..

Hi Ramakrishna:

Thanks for the suggestion, will try out using egg as food.

Tomorrow will inject another batch of eggs and try to raise as you all suggest here.

Hey gan...

This is d commonest problem i guess everyone face while raising our fish babies...we had d same problem initially but now mastered the thing...once u get the eggs and after they hatch feed them paramecium from day 5..let it be ther in d tank for an hour or half...change the water (1x e3 medium).....not upto until day 9 start feeding artemia..the thing is they dont have opening mouth upto until 72hpf, and the groove size is not enough to feed on shrimp from 6 days onward..so by day 10 start a mix of paramecium n shrimp...n by day14 fade off paramecium n just give shrimp...they will thrive better..make sure u feed twice daily n change the water after feeding is complete...in case paramecium is a problem u can give boiled n crushed egg yolk (dried overnight at 60 degree c)..n follow d same regime..

Guess this will help u in some way

@ Gan, I think, If the injection is not done properly, that also may result in death of larvae after 5 dpf. Try to change medium regularly and remove the dead embryos as soon as possible as they may increase the risk of fungal growth. I think, feeding will not be a problem. You can feed them with paramecium from 5dpf. Check the quality of injections and medium fro better survival rate.

Good luck!!

I would suggest looking into rotifers as a first feed. We recently switched from powders followed by artemia to rotifers followed by artemia and we have seen an increase in growth rate and survival. We are also seeing fish starting to spawn at two months instead of three. The people at Reed Mariculture have developed an easy rotifer culture technique using a 5 galon bucket (http://www.reed-mariculture.com/). There was also a nice paper published on using rotifers as a first feed for zebrafish (Best et al. Zebrafish 2010).

Good luck.

Use rotifers as a first feeding, and then slowly start to add artemia as they get bigger. Remember that they also need to be clean so keep that up as well. If food is left over, it will be detrimental to longterm survival.

We use hatchfry encapsulon starting at 4dpf. They are fed a few times a day with a light dusting. The Encapsulon is stable for 24 hours and it floats and slowly sinks. The tiny fry strike at the sinking food they do not forage the bottom. At day 10 I start feeding them decapsulated artemia (24 hr old nauplii). I dilute the adult concentration of artemia by 90% and spread the solution (1/4 ml per 5 fry) over the tank. That young, it seems the early developers will kill themselves eating artemia (digestive track appears to plug up) so the dilution has to be great-it is more to get them striking at the artemia. I increase the concentration approximately 10% each week. I feed them encapsulon up till 60 dpf then switch them over to 100% adult feeding regime. They don't seem to get fine attitudinal control until sometime in their third week. It seems to be at this time they start scavenging the bottom.

Water quality is a big issue. They seem to do better with some hardness and alkalinity and keeping the pH from large swings over short periods of time. Although the fry are better at tolerating increased levels of ammonia, nitrites and nitrates than adults there is a limit. Fry are intolerant of low oxygen-adults can handle lower oxygen than fry. If your ammonia is going up there is bacterial activity and you can be pretty sure your oxygen is going down. We do twice daily (approx) 80% water changes until they go the system. At around day 8 they go on drip. I daily monitor the ammonia and nitrite levels and do extra water changes accordingly.

If we can keep all the water parameters stable we usually have a really good survival (monitoring out to 3 months).

@Daniel : could you precise which rotifer product from reed-mariculture you use (since they have several). Thanks in advance.

Additional comment: artemia nauplii is the standard but it is a poor diet because it brings little energy and lipids…

We use Brachionus plicatilis (L-Type). I think this species is what most zebrafish groups are using. Don't hesitate to contact the people at Reed Mariculture. They are great and they have helped many zebrafish groups get going with rotifers.