At last, my tadpoles have appeared. I have no idea what is going on. For the last few years, I have checked at regular intervals to see if there was any spawn in my pond but nothing. (That I could see) There used to be great clumps of it all over the surface. Then, when I had given up hope, suddenly the edge of the pond was black with taddies. Last weekend my visiting family informed me I had lots of tadpoles, found by the visiting small person who was fascinated by them. So I can relax. I find lots of frogs and toads in the garden and knew they were hatching in my pond, but where is the spawn being laid, not on the surface as before. Maybe lower down under the floating pond plants.
I think if it sinks it dies, so near the surface attached to weed mostly in my pond. I have a separate tank for frogspawn as the fish eat them in my main pond.