you must find the source
whats your clean up crew?
do you sue RO/DI water, or tap?
What are your nitrated, nitrites, and phosphates
What sized tank do you have
how old is it
what kind of fish, how many, how big?
what kind of lights do you have, how old are they?
Crushed coral traps uneaten foods and converts it to nitrates to fuel alage growth