try pre-diluting the med. so if you need to add for example 1ml for 5 gal and your bowl is 1 gal put 1 ml of med with 4 ml of water, then add 1 ml of the mixture to your bowl, hey presto correct dosage!
You can use medication in a bowl, just make sure you adjust to fit your bowl. ( if you are medicating for a 10 gal tank, just do the conversion to a 1 gal bowl). I did this and has worked various times, Ii actually prefer the bowl because the medication lasts longer, you should probaly put a heater in there. Talking about dropsy, my male CT died from it in Feb ( he was over 3 years old). I guess it was age because his water was pristine.