The wording seems off (is there a shorter way to word what the card does)

I'm not sure why you would want this to trigger during each player's upkeep. Why not just write it as:

"If enchanted creature is black, it gets +1/+1 for each Swamp you control. Otherwise, it gets -1/-1 for each Swamp you control."

Granted, that doesn't get rid of a blocker or let you swing with a big creature on the turn you play this card, but I'm not sure why those things were positives. On a separate sidenote, Quag Sickness cost . This seems better than that card, if you don't count the one turn delay. Granted, Quag Sickness was a common... but removal isn't often better when you increase it's rarity.

Thank you for the assist - I want the card to be conditional - I used your wording but changed the condition to when the creature becomes tapped - if the pump is permanent my feeling is that it would be to powerfull