Every year I used to get frogspawn in my pond: large lumps of it, but for several years now there has been no frog activity. I still have frogs, and also newts and some fish. The pond is roughly six feet long, three feet wide and deep. There is a small waterfall and filter system; the water is usually clear.
Could be eaten by birds or fish, have you tried netting the pond or trying to keep fish out of one part of it perhaps with mesh or similar or perhaps make another small pond without fish.
The pond on my allotment had one or two frogs in it until bighting water beetles came and took it over. The frogs go to another pond for spawning so I see the young ones late in the summer but never spawn in the pond.
You can also get a boom-bust cycle between frogs and newts. Newts eat frogspawn and small tadpoles; this leads to an increase in newt numbers, but as the newts increase the number of frogs decreases. Then the newts have less to feed on, and their numbers decline, so the frogs start to increase again. And so on, at least in theory! We used to have frogspawn too, and then the frogs were replaced completely by large numbers of newts, and now the frogs seem to be coming back a bit - but I still haven’t seen any frogspawn for quite a few years.
That is interesting, there used to be an experimental pond array at the uni, loads of small ponds. Some of them were packed with both frogspawn and newts.
I think it’s probably a theoretical model that works differently in different ponds. Ours is small and gets very little sun, so that may also have an impact. The newts have continued to thrive for ages after the frogspawn stopped, so they must find other things to feed on!
Just found a useful piece on this on the Froglife website - final question and answer on this page: https://www.froglife.org/info-advice/frequently-asked-questions/newts-behaviour/