Abid222;4002524; said:
The possibillities are
The temp is a little low. I would bump that up to 82 for sub adult sized fish over 6". And 85 for cuda's under that.
And it may be possible that the crays are causing some stress. Because they are predators and jump at any chance they get to grasp a fish for a snack. Although I do have 2 5" blue crays in my payara tank. But if I could catch them with out dismantling the tank I surely would because i have seen a claw mark on one of my scombs.
And the filtration is some what low. The fluval 404 puts out 317gph loaded with clean media and goes down from there as it gets dirty. So at its peak effciency you have about 4 turn overs per hour. And since cuda's like current I allways try to aim for atleast 10x turn over rates with my predatory characins. I would suggest adding a Aquaclear 110 HOB style filter to the mix. Because they are fairly cheap, as you can find people on here and ebay selling used ones for 40-50 bucks all the time. And because they are cleaning monsters and there media is cleanable. So there's no cartridges to buy ever.
I would bump the temp first and then work on the filtration and see what happens from there. And just keep a eye on the crays for any aggressive behaviour towards the cuda.
Hope that helps
