That rules out most Plecos... Plecos are fairly shy and many are nocturnal- my bulldog took months to come out whilst I was around during the day.
Even so- I wouldn't describer her as active... and when she is active she's on the sides of the tank eating biofilm... NOT on the bottom.
I've noticed my Aeneus corydoras are more active than my Palaetus- other species I couldn't say- but the Aeneus are far more active. (the advantage of the Palaetus is that they school a little more- although still it's only a loose school).
Corydoras .. often take long naps during the day though and like to hide out under the caves for a while out of the light. They're not hyper-active by any stretch... Food gets them moving though!

Few sights are cuter than a group of Corys all gathered around eating from the same pellet.
Active and bottom dweller don't always go together- I personally love the Kuhli loaches- but again- they'll hide more often than not.
Thinking outside the box: Cherry barbs are fantastic little fish that are often overlooked. They're not true bottom-dwellers and so most people wouldn't consider them for this topic- but they certainly prefer to occupy the lower half of the tank that the top- and will help clean food off the bottom... they're more active than most corydoras or Plecos- not in the least bit shy- very colourfull and very hardy.
If it wern't for the rams I'd suggest ghost shrimp... mine were shy at first but after a few weeks became active and scurried along the bottom everywhere- your problem with them though is your choice of fish would find them tasty.
Still- if you don't mind them being feeders they'll entertain for a while.