until you figure out the root to the problem it is going to haunt you for awhile. fish snails liquid phosphate removal... etc. is just a bandaid to the problem.
its either one but most likely a combination of things
overfeeding corals or fish
to much light
to close to an open window with direc/indirect sunlight
to high of temperature and or temp flux
light bulbs are old
lack of efficient skimmer
lack of water changes
water changes with dirty water
death of a bunch of organisms
lack of adequate flow or powerheads
thats all i can think of now
its either one but most likely a combination of things
overfeeding corals or fish
to much light
to close to an open window with direc/indirect sunlight
to high of temperature and or temp flux
light bulbs are old
lack of efficient skimmer
lack of water changes
water changes with dirty water
death of a bunch of organisms
lack of adequate flow or powerheads
thats all i can think of now