05-18-2010, 01:08 AM
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There are a number of possible reasons for their changed behavior. The first one I would have to ask is what are your water params for ammonia, nitrite, nitrate, and pH? Changes in water chemistry over time, due to the growth of the fish, without accommodation of increased maintenance, can cause the behavior you describe. Fish that don't feel good don't feel safe.
As the fish grew did you increase the amount of decor in the tank to allow them to find larger territories to accommodate their increased needs? Fish that outgrow their environment can display the behavior your describe. You listed the fish, but you didn't list how big each one is? That makes a huge difference.
It is also possible that something spooked them at some point when this all started, and you may not even know what it was or that it happened... if it came from outside their tank, their behavior would make perfect sense. Until they feel secure again in their environment, the behavior will likely continue.
Foods being offered can also cause this behavior. What kind of variety do they have in their diet besides the krill? Do they react this way to all foods or just the krill? When a fish isn't finding proper nutrition in its food it will eventually lose interest and appetite for that food. With no reason to come out of hiding, they go about their business and find the addition of such foods as an intrusion instead of dinner.
Try approaching the tank very slowly, whether its feeding time or maintenance time. Every movement around the tank should be slow and steady, always controlled so as not to spook them. You can try taking 1 finger slowly to the glass and rubbing in slow small circles to teach them to come to you when you "call" them. This takes time and lots of patience, but I have not found a fish yet that can't be taught to respond if the conditions are proper and it is done right.
I hope this helps.