Well, as long as you don't let it get in the water it should be fine, but personally I would not take the risk unless you had a serious infestation on your hands. If you are going to do it, use the oil on a clothe and wipe it on the affected areas to prevent leeching of the oil into the water.

Lizards and frogs are another good way to control problematic bugs.

Is neem oil harmful to fish and amphibians?
http://www.discoverneem.com/is-neem-...mphibians.html

PAN Pesticides Database - Chemicals
http://www.pesticideinfo.org/Detail_...Rec_Id=PC35751