So much misinformation, where to being!?!?!?!?!
Algae dust you are describing sounds like mustard algae and is caused by not having a high enough FC level in the water. Once you get it you are correct that it is hard to get rid of.
Quote Originally Posted by wapate View Post
I'm sure the PH has not always been in range, but from the looks of the pool, it's been pretty close for 14 years.
<facepalm>
The calcium scale "cake icing" is a water balance issue. Peroid. You cannot tell if the water has reached scaling conditions by looking at it AND YOU CANNOT TELL THE pH OF THE WATER BY LOOKING AT IT, YOU HAVE TO TEST IT! PERIOD!
Both of these together are a good reason to fire the pool guy and start doing it yourself since the fact that you have had these problems and
Quote Originally Posted by wapate View Post
My PH is hard to get below 7.9 and the alkalinity wants to keep dropping. When I do add acid, I walk it in small amounts. Any idea there?
I live in Destin.
As far as walking acid to lower pH vs slugging acid to lower TA, it's a myth that persists in the pool industry even though it has been thoroughly debunked many years ago! (The linked article is from 1995!)

IF you are having problems keeping the pH down in a salt pool lower the TA. The main cause of pH rise in a salt pool is from outgassing of CO2. Keep your TA at about 70 (and adjust calcium if needed to maintain your calcium saturation index). Keeping your CYA at the recommened maximum (for Jandy that is 75 ppm) will also help by limiting cell on time. You then want to maintain the FC level at a minimum of 5% of your CYA (so keep it no lower than 4 ppm at all times).
When you lower the pH (it makes no difference at all if you walk the acid or slug it other than potential damage you can do to the pool by slugging it) don't lower it below about 7.6 and wait for it to climb above 7.8 before lowering it again. The lower you put the TA the faster CO2 will gas off.
Adding acid will lower BOTH pH and TA but it will lower pH much faster than it lowers TA, Depending on the TA of your fill water you might need to bump up the TA from time to time with baking soda (in Florda that is doubtful) but you want to keep your TA at 70 ppm and don't worry about raising it until it drops BELOW 60 ppm.
To lower your TA it is a process, you drop the pH to 7.0 (and not lower to prevent damage to pool surfaces and equipment) and then allow the CO2 that has been created from the bicarbonate (TA) in your water to gas off. The act of adding the acid lowers the TA, allowing the CO2 to gas off brings the pH up without causing the TA to rise again. Aeration of the water will speed up the outgassing of CO2. There is a sticky in the forum with full instructions on how to lower TA if you need to do so.

Once you get your water in better balance and are able to keep it there you might consider adding 50 ppm borate to your water to introduce a secondary pH buffer (in addition to the bicarbonate buffer we call TA) that effectively holds the pH at around 7.7 to 7.8 for a longer time than without borate. As an added plus the borate has algaestatic action and will help keep the mustard algae at bay.

Bottom line is this, just because you have owned a pool for 14 years does not mean you have been caring for it properly (and it is not your fault because there is SO much misinformation that the pool industry keeps repeating, some of it because of ignorance and some of it to keep chemical sales at a maximum.
Now would be the time to learn what to do so you do not repeat the mistakes of the past (and if it were my pool the first step would be to fire the pool guy and take contorl of the pool myself!)