If you are using artificial water, a good brand of salt should have everything that you need.
What have you got in your tank? You should only be adding supplements if they are required.
I have a mixture of LPS and soft corals. I add calcium for the LPS and coralline.
I also add a very small amount of Strontium for LPS and Iondine for softies.
I use Natural Salt Water so I have all the elements that I need but I have seen greater growth after dosing.
I think most addatives are better for the wallets of the companies than for your livestock. I would never buy any 'remidies' such as algae fix or purple up.
If you think these are going to solve probs, they won't. Anyway, I dose according to the manufacture's specs, Iodine and strontium about 1.5ml per week. and calc daily.
Hope this helps :mrgreen:
Oh, and I use a good brand of activated carbon. Polishes the water and I can see better polyp extension on all corals.