Water hardness and fertilization

[mudskipper]

Hi everyone,

I have horribly hard water and finally bought an RO system to bring things down to reasonable levels. I have Taeniatus Bipindi and Kienke that have been in very hard water for a few months. They have been showing spawning behavior for the last 6-8 weeks with no results.

The hardness level in the Kienke tank is now around 60 from a previous 250+. Does that hardness affect the fish themselves causing sterility, or does the hardness prevent the eggs from being fertilized? I guess what I'm wondering is should I expect to wait a while before seeing any fertilized eggs while the fish recover, or will the newly soft water allow them to reproduce on their next try?

Thanks,

Mike

 

[dw1305]

Hi all,
It is a combination of factors and they combine to cause either failure to fertilise or failure of the eggs to develop naturally. I think that as soon as the fish are in softer water the probability of success should increase straight away.

I'll need to find the reference for the mechanisms of failure of spawning, but the sperm enters the egg via the micropyle, a tube with membrane wall ("chorion") of the egg, in soft water the tube is wide, in hard water it is thinner and it is thought that the sperm is impeded. It is also likely that the egg membranes become calcified in harder water, which may both impeded fertilization and also reduce their permeability to oxygen, potentially killing the developing embryo.

The other factor is that very soft acidic water has relatively few micro-organisms in it, meaning that eggs of "black water" fish tend to become bacterially or fungally infected very easily.

cheers Darrel

 

[mudskipper]

Thanks!

That's the answer I was hoping for. Now comes the hard part. Waiting for them to try again.

 

[gerald]

Somewhere long ago I'd heard that obligate soft-water fish kept long-term in hard-water could get mineral deposits that permanently damage the ovaries, testes or ovi-/sperm- ducts, making them useless as breeders (if mineral deposits in the kidney or liver didn't kill them), in addition to the egg membrane problems you mentioned. This may have been pure speculation, but it seemed to make sense. Like Mike Mudskipper, I'm hoping it's not true. I'll be interested to see what info you dig up Darrel. I suppose it might vary among species -- blackwater dwarf cichlids might react differently from blackwater characins, anabantoids, etc.

 

[tjudy]

I have been having some better success with preventing infection of eggs of softwater species by using catappa leaf. I think that the tannins are a mild antibiotic and provide the same benefit that very low pH does. I have not been using it with dwarf cichlids (yet). Soft water blue-eye rainbows (Pseudomugil sp.), tetras, danios and cory cats mostly.

 

[dw1305]

Hi all,

I have been having some better success with preventing infection of eggs of softwater species by using catappa leaf. I think that the tannins are a mild antibiotic and provide the same benefit that very low pH does.

I do the same as Ted, but usually with alder "cones". There is quite a lot of evidence for the anti-microbial effects of Terminalia catappa, and a few for Alder bark & cones (Alnus cordata/incana/glutinosa/rubra).

The methanol extract of the bark of Alnus rubra showed antimicrobial activity against Gram-positive and Gram-negative bacteria. Diarylheptanoid and its glycoside (oregonin) were identified as the two constituents responsible for this activity." from: SAXENA G. et al, (1995) "Antimicrobial compounds from Alnus rubra" International Journal of Pharmaceutical Botany 33 pp33-36.

I've not had a proper look through it yet, but Citarasu, T. (2010) "Herbal biomedicines: a new opportunity for aquaculture industry" Aquaculture International 18:3, 403-414 looks very interesting.

cheers Darrel

 

[mudskipper]

Interestingly, I picked up a few catappa leaves a month ago and started trying them in my kienke tank, leaving the bipindi tank alone other than softening the water.

After reading about their use with Betta breeding, they seemed like a good fit for the west africans as well.

I'll report back with results.

Thanks again for the responses.