Found out why so many fish died

[Dubby]

A simple vacuuming of the sand will not get rid of all your good bacteria. I do NOT change the sponge in my filter even though the manufacturer recommends that they are replaced every month EDIT: I wash them in old tank water

I only replace the filter wool (which I use as a prefilter) when it gets too dirty.

I also have a CAE who is about 2" long and so far he has not done anything vicious (had him for over 2yrs). He occasionally does chase after one of my mollies. I also have an SAE & a flying fox and the FF has established his territory and wont let the SAE get too close

BTW, I have a heavily planted tank (read overgrown ) so that maybe the reason there is no violence.

 

[enchanted]

First, he didn't just vacuum the sand it was a rebuild of the tank. The reason I recommended a bio-wheel was because of where the tank is and previous problems he has had with this tank.

As for CAE, I have heard the same thing that in some tanks they do fine and do not bother any fish, but in others they go after everything. It's a risk if you decide to leave them in, they may or may not go after any other fish.