Need Help With Possibly Stressed Fish

[Richspilla]

Hi I have bought a tank off my mate about 3 weeks ago it was used before. I have done a cycle and have about 12 fish in now I have read a lot about it a looked into it a lot but my fish don't seem to be swimming much stay on the bottom most of the time iv got tests for the water and do changes every week I was just seeing if anyone could help me please could they be stressed

 

[LyraGuppi]

We'll need a bit more information before deciding what's wrong.
 
How did you cycle your tank? When did you decide it was cycled?
How big is the tank?
What fish are in it?

 

[eaglesaquarium]

Richspilla,
 
 
You said that you have tests... and do changes every week.  What tests have you run, and what are the results currently?  Also, how much water are you changing each week?  And how big is the tank?