The less chemicals we dump into our system the better off that system will be, especially if no testing is performed to determine actual levels. If one does regular water changes, chances are Sr levels will be at or higher than NSW levels dependant upon brand of salt used, periodicity and percent of water changed. Reference Atkinson & Bingman 1999
Did you see a deficiency in your system which prompted you to supplement?
While I agree that in certian tanks the les chemicals the better however, what is the strontium being used for?
I think that regular water changes do replenish lost additives from the water however that are some additives that never will be replaced unless by other means. Basically, I do what my system responds too. If adding the chemicals is a healthier environment, I do it. Granted, the fewer chemicals used the easier it is on the ol' wallet!!
If you don't want to dose any stontium you might want to turn off your calcium reactor (if you have one) because along with releasing calcium, your calcarious medea also releases strontium.
Squamosa and deresas can be kept under VHO only. I have 2 squamosas and 1 deresa under 440w VHO. I have a maxima under 250w halides and a crocea under a 400 halide. I don't think halides are manditory for all clams. I also don't do any supplimental feeding for the clams. All have excellent mantle extention and color. Pics can be seen at my photosite.