What you can try to do to find larvae is if you are an early riser and it is dark. No room lighting either. Take a pen light or similar low light and place it near the top corner of your tank. The larvae are light sensitive and will be attracted to it. Within a very few minutes the larvae will be in that corner. Maybe too dark for pictures but seeing them should give you piece of mind. If this is too much trouble look for the larvae from the side of the tank. For whatever reason I can find them easier. Finally you could look near the substrate. If they are not in the water column they sometimes 'hide' mm from the bottom.