Warning for Indoor and Outdoor Aquarium Owners
I rescued few fish selling on the pavement (I haven't got enough space for all) with temperatures hovering around 32 degrees in Kandy city.
It must be worst in other districts.
Diurnal (in fact within 12 hours) variation of January temperatures are more than 15 degrees Centigrade.
Early Morning 20 degrees and at 1 pm 35 degrees.
Fish can tolerate up to 30 degrees indoors may be less outdoors.
If your fish are dying, it is not due to algal bloom.
Just keep an aquarium thermometer (very cheap) and test the temperature or cover the pond with (thatched ) coconut leaf or better light inhibitor polythene wrappings.
What I use is a polythene roofing cut into shape and paste the polythene wrapping with fish friendly silicone glue (used to paste glass tanks).
Industrial glue kills the fish.