Shad: You didn't indicate a brand-specific ear tag - which is critical, yet academic.

"Critical" since many insecticide-laced cattle ear tags contain pyrethroid or organophosphate insecticides - some of which could prove hazardous if confined with feed that will be ingested by fish.

"Academic" since insecticide-laced cattle ear tags are EPA-registered pesticides that include a statement on the package which instructs not to store them with food or feed. In my business, off-label recommendations are taken quite seriously - especially when a liability-issue arises. Be careful what you recommend!

Just because a pesticide-agent will work for any given situation doesn't mean that one may arbitrarily recommend (or use) it for that purpose.

There are other effective means for dealing with ant problems besides placing an inappropriate insecticide in close proximity to the fish food. Depending on the ant specie in question, there are several weatherproof bait-station products (ie. MaxForce ) which would avoid the potential of feed contamination.