water hardness and larval/fry growth rates

[fishgeek]

Hi guys,
have been in a discussion about discus needing harder water to grow properly as young

was wondering what the breeders here believe is the case

whether anyone knows why it might or moght not make a difference

whether discus breeding in nature occurs when water levels are prehaps receeding and water hardenss does maybe increase during fry development growht


I have been trying to do some reading into it and am just interested in experiences to go with some interesting theroy

cheers
andrew

[aussieorchid]

I found when I used to grow out large numbers of fry that they did better in harder water.Since the babies are growing at such a fast rate it would make sense they would need large amounts of calcium for bone development etc and the only way to get that would be the water or food. As they are in the water 24/7 that is where they will get the most of it.

[ILLUSN]

i keep a pouch of crushed coral in my grow out tanks for the bones as per advise from this forum, i've had no bad results from it, and my fish have never grown faster.

[fishgeek]

general internet consensus seems to be similar...
my logic suggests that calcium in water makes bugger all difference to , or in comparison with calcium in food
and that calcium levels alone are not of any value for ossification of skeletal growth, rather calcium phosphorus balanced .. not sure of ratio for fish is much more important


what i did find when looking for some answers to this is that calcium levels in water , seem to have some protective effects for fish ( in artificially acidified or polluted waters) against aluminum and some other heavy metal toxins...maybe a chelation effect
and that at sub-lethal levels growth rates were slowed and growth deformities were encountered...

could this be where the suggestion that calcium in water is encourgaing better bone growth?

there was an interesting study on varied levels of dietary vitamin supplementation showing low levels of dietary nutrition lead to death and higher levels had almost twice the growth rateshttp://ajpregu.physiology.org/cgi/content/abstract/00659.2007v1


i just found it interesting and thought others may aswell
some other links that i was going through ..

http://www.blackwell-synergy.com/doi/abs/10.1111/j.1095-8649.1982.tb04003.x
http://jeb.biologists.org/cgi/content/abstract/207/4/645
http://www.blackwell-synergy.com/doi/abs/10.1111/j.1095-8649.1982.tb04718.x

any comments or thoughts
andrew

[ILLUSN]

Good reading Andrew, maybe the faster growth rate I'm seeing is due to the disolved calcium helping to buffer against the low ph of my growout tanks?

[samir]

I haven't found any difference in growth rates with soft or hard water with my fry.

[fishgeek]

yeah possibly, just thought it was nice to try and understand why things are said, as the explanation for hard water adding skeletal growth by providing calcium seemed a bit whack to me... but hey i have neever kept discus


samir do you feed more live foods, one paper suggested commercial foods werent nutritionally sufficent and that live food helps avoid some of dietary deficencies(i think that was based on danio's - so maybe not exactly the same)

andrew

[samir]

never feed live food

with dry foods + daily 90% water change + harder water (bag of shell grit) + ph 7.5
5cm in 12 weeks

with beefheart + sera fishtamins + daily 90% water change + normal water (30-38mg/l Calcium Hardness) + ph 5.5
5cm in 7 weeks

imo beefheart is the best food for growth. If there is a calcium supplement it would be more convenient to add it to food,than to water, not sure which is more effective.