It is probably fine as. Long as the room your frogs are in is NOT cramped and with low ventilation. Smoke is also produced by candles and that can be overwhelming in a small room. One candle doesn't produce a lot into the air, but caution should alway be a. Priority when it come to the safety of your animals. If it were really harmful to them it would be to you also. Even though our anatomy and tolerances are as different as night and day you should consider shortening the duration in which you burn them and monitor any. And all changes in behavior. And activity. Remember that carbon monoxide. Is also produced from burning.