Major Changes in fish behavior.

After changing the filter, I cut the old sponge as someone suggested and
pushed it down inside the new bio filter, Ill leave it for a few days. But I
noticed the fish are very very active now. At first I thought it might have
had something to do with going from a 20 gal filter to a 40 gal filter (160
gpm). I decided to test the water. Water clarity is increasing, after the
loss of the other filter I had some serious cloudiness. But these are
current readings.

Temp: 83 f.
Nitrate: 20 PPM
Nitrite: 0 PPM
Total Hardness: 425 PPM (Something wrong here)
Alkalinity/Buffering Capacity: 180-240 PPM
Ph: Between 7.2 and 7.6

The fish are swimming around like crazy. They used to slowly swim around the
tank, now its all over and very fast. What do I need to do to correct any of
the above?

Thanks
J