WHY DON'T TROPICAL FISH EGGS HATCH?
By Jim E. Quarles
25-04-99

I know that with angels and discus this quite often becomes a problem that has caused many to give up attempts to breed these wonderful fish. This problem is one that is explainable in general terms, but can have specific causes beyond the known factors. So no study to date can explain each and every case.

In dealing with this problem in this article I will consider only those fish that require soft acidic waters, principally the Amazon River cichlids. When we speak of the Amazon River habitat, you should be aware the their are hundreds of rivers that flow into the mighty Amazon and each in turn has thousands of small feeder streams or creeks the add to the giant flow of water. Each can act as an independent habitat with its own water parameters.

One outstanding factor we have learned over the years is that for discus, angels and most tetras, soft water is required for their eggs to hatch once the fish have spawned. While it is very true at least for discus and angels, that you can keep them in hard water and have them remain healthy and active, you will have very few if any successes if they spawn in such water conditions.

It is believed the reason for this is that the carbonate hardness causes the outer egg fabric to harden, and the embryo can not expand as in normal growth in soft water where the outer shell remains soft and pliable.

Then the question comes to mind, how about the pH factor? Here again we have two theories; some breeders maintain the pH in the range of 6.2 to 6.8 and seem to have far fewer problems than those who keep the fish in the higher pH ranges above a pH of 7 or more. However I am not sure the pH factor plays a major part in the breeding if the hardness range is kept low. Sometimes the male discus will not reach a readiness to spawn at the same time the female deposits her eggs. In this case the eggs simply are not fertile and of course have no chance to hatch no matter what the water conditions maybe.

Many times the current of the water flow from the filter is such that the male's sperm is simply washed away from the eggs before the eggs are fertilized. This happens to be the case in more breeding attempts than you would think.

When the pair locates a spot to lay their eggs, you should reduce the water flow to as low a rate as possible and direct it away from the spawning site. You would be amazed at how many times this simple adjustment can make the difference between a live spawn and dead eggs.

One other consideration comes to mind, some males cannot spawn they are born mules, they will never produce fry. I have noticed this to a much greater degree in Golden severums than discus, but it happens to discus and angelfish also.

With all the inbreeding that has been carried out over the past few years it is to be expected that a few mules will be produced. With line breeding the fish also get smaller and smaller as adults, even under the best care.

EGG EATING DISCUS PAIRS.

Sometimes you will be the owner of a pair of discus that will lay the eggs then as fast as they are deposited the male will eat them one by one. In other pairs the laying part is successful then both pairs will after a short time eat the eggs. You can expect this with very young pairs the first couple of times they spawn. After all, they have to learn to care for the eggs and fry. While nature gives them the hint and desire though genetics, it is still a learning experience for most pairs.

You will also find that some males will just not fall in love with a given female and will not respond to the egg deposit, yet when placed with another female will become a great parent. Last but not least some pairs get along well together until the eggs are deposited and both have done their jobs quite well, but shortly they begin to fight over the care of the eggs, this will most likely lead to one or both eating the eggs. When I have found a pair with this problem I simply remove one or the other and let one fish tend the eggs and resulting fry.

I am sure there are other reasons why eggs fail to hatch but the above covers or explains 95% of the problems normally found.