Thanks for that info Yonny ,very helpful .I've had my integrated UV bulb light going for nearly a year ,so that's what I'll change first ..
I got three marginal plants in suspension cages in the pool ,but they need cutting in half and replanting in new aqua soil as they gone a bit mad ,then I'll have a look at that chemical you saying about ..
I bought a Solar ,flashing ,noise making anti rat ,cat deterent,box it seems to work ,Seagulls hate it ..
It's only a small water feature ,but I absolutely love it ..especially when the fish swim past a viewing porthole ,...plus lol,they like tiny amounts of ressi specials ,crumbled as a treat occasionally...those fish literally know I'm about ,especially as I feed em same time same spot ,which is interesting especially if crossed over into angling mindset ,they become trained !!!!