Why won't discus eggs hatch in hard water?

[Carol_Roberts]

Tony S. has provided a very clear explanation I wanted to share with you.

The eggs will still be fertilized in hard water...maybe to a lesser extent due to the sperm not being QUITE as viable in hard water(nuther area all together) The problem comes AFTER the eggs are fertilized....in hard water, the embryo suffocates due to the fact that the egg shell calcifies and osmosis CANT take place.

Thats the reason many fish speicies fan thier eggs....to promote a higher level of osmosis which in turn feeds the embryo more oxygen.

Tony

[Ryan]

I have never actually read a detailed explanation of why hard water is bad for the eggs. This info is very helpful. Thanks, Tony ;D I knew that fanning oxygenated the eggs (if you remove angel eggs from parents, you have to put an airstone over them)... but I'm just curious as to why angel eggs don't die in harder water? I thought they were from the same waters as discus. Is there any explanation as to why angels have adapted to spawning in harder water, and not discus?

Ryan

[Jason]

i'm confused, i've pulled eggs from tanks and have had them hatch in pure ro waste water.

IME its not the conductivity, its the high ph that prevents good fertilization, wich leads to low hatch rates!

[shamsoo]

good thread keep it going,

[Kagan]

Well from my experiences it is not the PH.. I have had very good hatch rates at 7.5-7.7 PH (about 85-95% in different spawns).. In fact, the male is able to get used to the water conditions. It is the hardness that effects the egg wall. As a result, it leads to non-hatching of the dotted eggs... So here, I agree Tony..

Kagan

[cobalt]

hi fellows ,
did Tony test motility in hard water?

Sorry but i beg to differ .I had a Phd student named tidhar, she tested tilapia sperm in diffrent waters and it didn't really differ in tilapia,
Any way I have a diffrent theory.
I took fish eggs and put half of them in r.o. water (real low conductivity) and the other half in water from my intensive system (1450 microsimens) .
The sperm enters the egg via a tubule in the animaly end of the egg ,it is called Micropyle.
The micropyle is a tube with membranal walls , in soft water the tube is wide in hard water it is thinner and we think the sperm has a hard time getting thru, we have electron microscope pictures proving this in tilapia who is a hard water fish, In discus it must be much worse. Anat Mor and Leah Reich published it in 1992 (or so).
we don't have pictures in discus but we assume it is the same.
maybe discus sperm is slower in hard water who knows?

What do you think?
Cobalt

[Jason]

I don't disagree with Tony at all, just in the few experiments I've done(and I'm nowhere near a scientist, I cant even make toast) it just seemed like ph was more important to fertilization and hatching than condustivity.

Is Hardness, Conductance a indicator of osmotic (sp) pressure in the water?

Ronald

Let me rephrase that.

In the early 80's I have learned that the osmotic pressure would have something to do with the hatching or not hatching of the eggs.
Not being interested then I have not noted it nor do I remember today from where I learned it.
Is that a myth or is there something to it ?

Thanks for any respond
Ronald

[kevster]

[quote author=Ryan Smith link=board=6;threadid=7851;start=0#83935 date=1047285301]
I have never actually read a detailed explanation of why hard water is bad for the eggs. This info is very helpful. Thanks, Tony ;D I knew that fanning oxygenated the eggs (if you remove angel eggs from parents, you have to put an airstone over them)... but I'm just curious as to why angel eggs don't die in harder water? I thought they were from the same waters as discus. Is there any explanation as to why angels have adapted to spawning in harder water, and not discus?

Ryan
[/quote]

that is not true at all. I remove the angel eggs and put them in a shallow pan of water about 3/4 of a gallon and I do not put an airhose in the pan until they
are freeswimming. Maybe fanning oxygenate the eggs but you certainly do not have to.

[THEDISCUSGUY]

HEY ALL
i dont belive that ph has to be low to secessfully breed discus. i belive that the discus get use to the water that you keep them in, with one of my breeders i have left the same water till the eggs hatch.. those babys grew up to be perfectly fine.. not sayin that my water is dirty. but that i belive that they will breed if the water is stable and is kept stable. because i do alot of water changes the water is just the same as the tap water. but this is just how i breed my discus and i have so for yrs
dale

What Have I started here!! ;D

Let me start off by saying...Im no "expert". Far from it as a matter of fact.
My statement above is based purely on 11 years worth of Breeding, reading, and talking to fellow hobbiests and breeders.
One thing Ive always found with MANY aspects of discus keeping/breeding, is THERE ARE NO ABSOLUTES. Particularly when it comes to water chemistry and breeding.
The statement I made is a "blanket statement" That I believe to be true In most cases. But there are always exceptions. IMO though...I believe the "exceptions" are due more to a particular fish's heritage, genetics, etc. Rather than saying all discus can/could be successful in hard water.
There's no question in my mind that SOME strains/color types are not as fussy about water chemistry as others are....while some need very specific water perameters to get a good hatch.
I dont really want to get into "area specifics" here....simply because of the fact that even though MINE and YOUR water may have the same pH and hardness....they COULD(and probably are) still be completely different in make up ie....salts, acids, bases and how that pH and hardness is achieved.

Cobalt...
I would be interested in hearing more about your students tests. Sounds really interesting.
Are the eggs tested fertilized? if so...how ARE they fertilized? In the cunductance you mentioned above?
what type of water are the females kept in prior to testing? Do the micropyles shrink while the female still holds them? or once they are layed? I have FULL respect for the work youve done....but there are LOTS of questions to ask.

I'll be back ;D

Tony

http://forum.simplydiscus.com//index...d=7891;start=0

Sorry, I just noticed this thread after beginning the one on the link.

I just switched from using RO/tap water on my water (cond 250ms, pH 7.5) after _david_ had breeding success with his tap water (cond 550ms). I've got as many wrigglers on the cone this morning as I have in the past with RO/tap water.

Dave

[cobalt]

the work was simple
We waited till the female started to spawn then we removed he and the eggs spawned. Then we proceded to strip the female genetly into a petri dish with tank water and .5% eagle medium withour Ca+ (I think it is called MEM)
we then striped the roe from the males into a vial with medium.
this we believe keeps the eggs and sperm in physiological status.
I will look for the paper and post the location of it.
All tests exept the vitality Vs time , where conducted within 25 min.
Tidhars Thesis is still in publication. she duplicated the results with ram sperm but found some diffrences.
In my opinion questions are welcome, We are here to learn and teach not hoard info! ;D It also keeps us on our toes! :P
Cobalt

[Ardan]

8)

Very interesting thread!
Good thoughts and good questions.