I'm sorry you haven't gotten a response by now......I'm not sure that I understand the question. Are you saying that when the pool is on, your water is changing color due to "stuff" coming from the heater? Do you need the heater in Florida? If not, I would completely bypass it or remove it altogether. If the "stuff" can be vacuumed, do so....if it's staining (possible if it's green), try just shocking the pool for an extended amount of time to see if the stain will lift, and if not, then try the metal sequestrant method that mbar describes. Why does the service guy think that you need to drain and acid wash?

Janet