Why?
Because you threw out advice without dosage recommendations, any warnings or letting the person know of any side affects that can happen.
Chemicals are not the best option without finding out the root of the problem.
People have lost an entire system by adding chemicals or improper dosing because they were just told to "use that product."
From the other thread, a link was supplied explaining cyano & advice was given regarding husbandry, flow & water chemistry....
to then just see "I would use Red Slime remover"
again....not good advice.