Got rid of the goldfish now my tilapia are shy

[mario cole]

I started off my 150g system with a bunch of feeder goldfish and when I got some tilapia they lived with each other. But then I started having trouble with nitrites and the water got a little murky so I started removing them. After a lot of nighttime ambushes they're finally gone but now the tilapia seem to just hide on the bottom towards the back of the tank and don't always come to attack the floating pellets.

I've also had to run the table saw in the room they're in this weekend, dunno how sensitive they are to loud noises. 

They're also living in a bit of algae popping up after I added some filter media in an overflow box.

So many factors lol. Guess I better do a water change to clear things up a little anyway.