If you have any antifreeze in the garage, you have a chemical (ethylene glycol) that you can use as a surfactant. Whenever I suggest that it can be used as a "sinkant" to break surface tension, someone always reminds me that it is toxic. It is but in the amount used to get a fly to sink is negligible. Propylene glycol that is marketed by Kodak as Photo-Flo is also a surfactant that prevents water spots during film development.