Advertisement So, when I clean out my roach bins I save the frass for my plants. I had a momentary laps of judgement and gave them fish food instead of dog food, and now there's fish food mixed in with the frass. Is there a reason I shouldn't give the plants the fish food frass? Indoors, I have a few pothos, a spider plant, and a hypoestes. Outdoors I have a Mr. Lincoln rose, and a strawberry. I think the strawberry is a quinault.