Raising fry

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sfsam

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Hi all, my first post here so I'll give a quick who I am and then get to business. I've been in the aquarium hobby for nearly 30 years. I have kept a wide range of fish and bred a few, mostly to raise my own numbers or supply a few to clubs, family and friends though I have sold some locally off and on.

I never kept Cories until this year and finally couldn't resist. I've moved a few years ago to very hard water and have found many things especially in breeding a bit more touch and go.

I picked up 5 Cory aeneus, 3 females, two males and they started breeding in QT so I decided since I wanted more anyway I'd raise out a few babies. That was in April/May and I'm still stuck. PH 8.2, kH 10, gH 15-16. Their tank has never hit nitrAtes of 20, was started with cycled media and they have no tank mates. I experienced failure to fungus for many many batches even using MB and separating eggs entirely until I got enough flow in the tank. Adults "mostly" leave eggs alone anymore, with that I've been leaving them in the tank. Now I can get the hatch about the time fungus starts on non viable (unfertilized) eggs... But I cannot get fry to survive past 5 days and have a very high mortality rate within 24 hours. Example of 72 viable eggs two weeks ago that hatched, I had two survivors at 24 hours and 1 lasted until day 7 that was my longest lived fry. Would the fact that fungus started on non viable play into my fry survival? I do remove non viable as they show signs of fungus but some may sit several hours while I'm at work and fungus does spread quickly....

I currently also raising a tank of CPD fry and have a huge variety of fry food... Sera micro, 5 micron golden pearls, decapaulated baby brine shrimp, frozen baby brine, daphnia and rotifers (also both frozen).

I understand adults aren't known for eating fry but after each hatch they will neglect to eat their beloved foods at all for 2-3 days so if that's pertinent I'm tossing it out.

All comments and help are appreciated and if necessary I do have a RODI system so I can make whatever water is needed but I've found no information leading me to precise parameters that may even help increase survival, though I am aware bringing params down to around 7.4-7.6 pH, and kh 5-6, gH 8-10 would likely help prevent fungus will less flow.

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If the GH is 15-16 degrees, as opposed to ppm or mg/l, this is probably the problem with the cories. I am rather surprised that the eggs actually hatch, as the calcium in harder water usually prevents this, or can kill sperm. But it will also affect the delicate fry. Cories in nature never live in water anywhere near this hard, and while some species especially those commercially raised for decades now can manage as adults, eggs and fry may not.

The fungus is probably due to the eggs dying. Cories do not look after the eggs like some other fish such as cichlids and loricariids to "remove" dead eggs, so fungus can be more of an issue.
 
I can say yes I've had a varying percentage of eggs that were otherwise viable not hatch sometimes an entire clutch. I fear softening the water too much but am happy to acclimatize over the next few weeks and maintain the new parameters. What parameters do you think would bring about the best success?

Honestly I'd like to prevent the hassle of remineralizing straight RODI and simply dilute my tap to necessary parameters since when I get to raising the fry I'll be doing frequent water changes which during my work days will exceed my avaible time to do as frequently as I like. But if it's necessary I can make water from scratch.

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I can say yes I've had a varying percentage of eggs that were otherwise viable not hatch sometimes an entire clutch. I fear softening the water too much but am happy to acclimatize over the next few weeks and maintain the new parameters. What parameters do you think would bring about the best success?

Honestly I'd like to prevent the hassle of remineralizing straight RODI and simply dilute my tap to necessary parameters since when I get to raising the fry I'll be doing frequent water changes which during my work days will exceed my avaible time to do as frequently as I like. But if it's necessary I can make water from scratch.

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I mix RO with tap water to get to the desired levels. No issues with this but bring the hardness down gradually to reduce the risk of osmotic shock. You should also keep an eye on your pH. Your GH and KH will be reduced in the same ratio so this may be a consideration in your case. The KH in my tap water is over 20 degrees so in my case using 2/3s RO leaves me with a KH of around 7. My pH has dropped from 7.8 to 6.8 which is exactly where I want it to be but my starting point for KH was double what yours is.
 
I was thinking start with a 3:1 and see where it gets me as that is easy to acclimate and I know my kH will be solid still below that I would heed caution of course and monitor closely but I have kH additives for my shrimp on hand so if I start getting lower below 4-5 on kH I can always bump it up without bumping gH and still keep those TDS levels very low. I can bring into any parameters but the less the better as I don't plan to continue long term breeding project and hope, eventually to be adding the entire group to a community tank that's at my tap so closer I can be the better.

And thank you. The hard water here continues to present me challenges and I genuinely try not to blame it for issues but, it does seem to play a part in many of them lol. I guess I consider myself blessed to understand the chemistry well enough to safely make changes necessary while almost always keeping it stress free lol at least for the fish! I have a tendency to get a little anxious about them sometimes [emoji28]

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If you mix "pure" water such as RO or distilled or sometimes rainwater with tap water that has a high GH, the mix is proportional. Example, mixing half tap and half pure will reduce the GH/KH by half. The pH will tend to lower as well, depending upon the initial levels of GH/KH.

I am thankful I have never had the problem of hard water; my water is very soft, next to zero GH/KH. I add nothing to raise GH/KH, as I only keep soft water fish. Most are wild caught, including some 50 cories.
 
Yes quite true Byron! I'd just like to start with params as close to my tap as possible saving acclimation difficulties coming back around. I don't necessarily consider the hard water here a problem or a burden, just a challenge [emoji6] although I do look forward to getting back home and having some solid parameters mid range where a bit of cuttle bone or coral keeps and old tank stable and the water doesn't leave rings in the tank to contend with weekly lol

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