Medaka eggs aren't hatching

Discussion in 'Breeding Fish' started by Medaka, Jul 11, 2015.

  1. MedakaNew MemberMember

    Hi, I am in need of some serious help! I am trying to breed and rear Medaka/Japanese Rice Fish/Oryzias Latipes. The breeding adults are in 10 gallon aerated tanks, as well as AHAB units, supplied with pond water. The combined average of all fish is 200 eggs daily, but there are many days in which 400 eggs are collected.

    PROBLEM 1: The AHAB unit fish do NOT produce eggs nearly as well as the fish in the 10 gallon tanks. The 10 gallon tanks have 7 to 10 fish in them with male to female ratios of 1:1, and produce anywhere from 20-70 eggs daily. The AHAB units have male to female ratios of 1:1 or 2:1, and range from 2-5 breeding fish in each unit, and produce 0-10 eggs daily.

    PROBLEM 2: Once collected the eggs are placed into dishes with rearing solution and meth blue. Unfortunately, only about 12 fry result from the daily 200-400 eggs. I cannot figure out what to do.

    The eggs that do not hatch are turning a cream color. I am thinking it is water mold, or possibly Ich, but I am leaning more towards the water mold because the adults are without white spots.

    I clean the tanks multiple times a week. I haven't had a fish die in weeks; when a fish does die the tank is cleaned and tank mates are treated with meth blue.

    I keep a daily record of the water quality, checking: temperature, pH, nitrites, nitrates etc. The temperature is 75 degrees F, and everything else is normal.

    Please help me figure out why I am not producing more fry.



    Last edited by a moderator: Nov 23, 2018
  2. virusmkWell Known MemberMember

    Dont know much about them but if eggs go white or creammy as u said there are 2 things to consider.

    1 Might not be fertilized.

    2 Water conditions are not right.

    If not apropriate ph /kh amonia or high nitrate can contribute towards poor success.

    Have little experiment and do one dish without any meds only clean water and water conditioner nothing else in there and see if meds have some sort of effect as my understanding is to give meds only to ill fisn not to those that are not.
  3. chromedome52Fishlore VIPMember

    What is the "rearing solution"? You should be placing the eggs in clean water, with nothing else in it. Alternately, use water from the breeding tank. Meth blue is not a medication, it is a dye, and it's sole purpose is to reduce the exposure to light. These eggs don't need that. It can cause as many problems as it prevents, and for Oryzias, it prevents nothing.

    My preference with these fish is to remove the parents and let the eggs hatch in the breeding tank, but that is because I don't want to raise a thousand Medakas! This is a very easy fish to breed, and it sounds to me like you are being over cautious.
  4. MedakaNew MemberMember

    I have been following a book for Medaka cultures. It says to use meth blue to prevent fungus growth, since it is a dis-infectant, anti-fungal,and anti-parasitic.

    Rearing solution: "1.0 g NaCl, 0.03 g KCl, 0.04 g CaCl2·2H2O, and 0.163 g
    MgSO4·7H2O in 1 L of water"

    I don't think that I have enough tanks to remove the adults and let the eggs stay in there. I have about 40 tanks of Medaka,not including the juveniles and fry tanks.

    Can you think of anything else I could do?
  5. chromedome52Fishlore VIPMember

    I don't think you are supposed to put the eggs into the rearing solution. It's essentially a saline solution, and you are putting eggs from fresh water into a rather significant solution of salts. I believe you are supposed to mix that solution in a bottle/container, and then put just a few drops of that into the hatching container with fresh water. This is what some Killifish breeders were doing back in the 1980s, when they found that the antifungal they were using was causing the eggshells to harden, preventing them from hatching.

    I have raised these fish, as well as three other species of Oryzias, and they really do not need all that. Putting the eggs in with Meth blue is believed by some to do all those things you mentioned, but I have a chemist who worked for a major drug company who tells me it does not, other than by reducing the light getting to the eggs. I stopped using it 20 years ago, and have had better hatches on Killifish, Ricefish, and Cichlids than I had using Meth Blue.
  6. HarlebleondoraWell Known MemberMember

    I hatch and raise a small colony of gold medakas, I have a roughly 80% egg to fry survival rate by putting the eggs still attached to the moss over a home made sponge filter. Try keeping the eggs in a path of water movement (Over bubbles, near a filter outlet.) in a larger filtered container, Medaka eggs can take as long as 3 werks to hatch. A larger container with filtration and water movement should help prevent fungus.
  7. IchthiusNew MemberMember

    What are your water quality parameters?

    How dense are you storing the embryos?

    What are you storing them in?

    Can you confirm early development?

    They should hatch in 250* Celsius (250/incubation temp= days to hatch).

    Which book do you have?

    Why are you trying to produce so many medaka?

    Research? Where?

    I work with zebrafish and keep medaka as small part of my hobby.

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