interesting behaviors - any idea what they mean?

Hey All ~ I have a 75 gal tank that is currently housing about 30 south american cichlids of various sizes. We started with 10 fish 2 years ago. Different pairs are always having babies and 1 or 2 manage to survive each time. My fish are hilarious!! I love watching them. Within the last few days things are picking up in there home....spring is approaching..is that why (longer days, warmer water)? They are REALLY getting crazy - super active and moving the rocks around, chasing each other, exchanging hiding places. I wouldn't call it aggressive behavior - there are no physical signs of distress. Pairs of fish will circle each other the way dogs do in a park, but of course much more eloquently and fast as sh$%t. What are they doing? I think they are courting but what do the experts say? Also, one fish sortof got the shakes today - he just sort of rapidly shook all over like he was shivering for maybe 15 seconds. What was THAT all about?

One more question.....we only feed our little guys once a day - it takes about 10 minutes. Is once a day enough, especially when they are so incredibly active? I am assuming since they are growing that they are getting enough but....

Thanks for your advice, Teri-)