Please help! Sterbai Cory unexplained deaths...!

[Warrior-Lady]

F FJB and others thanks for your replies, and happy new year to all!

I purchased the tank complete with substrate and don't know any specifics of what it is. Here is a pic I managed to get of one of my cory's eating an algae wafer - you can just see his barbel, I think he's missing the one on the other side. Hopefully this can also give you an idea of the substrate?

As well as the sand I have added river rocks, some as caves for my kribs and a few others scattered here and there.

Please let me know if any other photos would be helpful! Many thanks

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I have 23 cory's all on smooth gravel as it doesn't hurt them as soon as i saw your picture, the substrate is to sharp and cory's dig so this would rip their barbels away. It's like grit sand and i'm not being funny towards yourself but your water qualities are Ace but that brown needs removing besides substrate.

Corys love either pure sand or smooth gravel.