I think the question was; does your teachers tank have any LR
? What type of substrate? I can't believe the intake on a 330 would cause that. I think his fish are dying and ending up there. The flow rate on a 330 isn't that strong as to suck a fish in it. I still have 1 FW
tank and it's 20 G standard with a 330 on it. In there are 1/4" neon tetras with o problems at all. It sounds to me like the tank hasn't cycled properly. Have water tests been done?
And for the record Luntiz you are close but not entirely right. Both mechanical and biological filtration is needed but how it is provided is the relevance here. With enough LR
yes biological filtration is provided and no manufactured filtration is required. Mechanical filtration is that of actually removing waste from the water, in this case the CPR bakpak is the mechanical filtration. Without LR
or other form of biological filtration this tan appears to be doomed. Another filter won't help at this point as their will be no bacteria colony on the media.
It sounds to me like this tank needs help fast.