might need a bigger pump-
i concur. you probably used a pump too close to your limits. over time bio slime builds up and restricts flow rates. always spec a pump at least 1.5 times more gph than you think you need.
you might also have some crud blocking the inlet to the pump impeller.
In my opinion, with a 140 gallon fish tank you should use at least a pump that will cycle that volume per hour. For enough filtration though you need at least 140 gallons of bio filtration and will need to cycle smaller grow bed areas more often.
What size pump have you been using? The slower the flow, the quicker that pipes are prone to plugging. I'd suggest a Danner 200 and probably another grow bed. And a sump.
Open up the pump and clean it out. The magnetic impeller will pull out - just clean all the slime off of it. I like using a micro-fiber cloth - just wipe the pump out and it's ready to be put back together.
Yeah, an upgrade is in order. But even with a more powerful pump - don't forget to open it up occasionally (at least quarterly i think) and clean it.
I've been told, and have done this myself, to take out the mesh filter in the pump (if there is one). I've never had a pump problem since I did that. But it wouldn't hurt for you to get a 300-400 gph pump for proper flow.