Since the good bacteria are dormate, and the water is still a bit cold...you might clean out your bio. I do this yearly, since my system is not to big. This yearly clean out save me from having any problems goin into a full summer of feeding. After clean out you treat the water with quick cure, paracide green, proform c to kill off any bad bacteria you may have stirred up clean the chambers. Also wihile you are at it you might want to treat the pond with superverm to make sure. From there you should be feeding light anyways, since the temps are not hot enough to feed higher protein food. You can use Microlift to boost the bio or a product called ABA....When the bio becomes back online in 2 months after cleaning it is ready for summer feeding.....