I agree with everyone especially Yoda,
Just as a normal practice, you should use the Mosquito Dunks, Everytime you water. Just to be on the safe side, gnats or no gnats.
Speaking of which:
GoGnats - it is a natural product, liquid form
Gnatrol - It is a natural product in powder form
both are systemic
The Dunks cost less, and since I have used all three, I think the dunks work the best.
just sayin'
bye for now
Peace
Eek