I can only talk about Ocean's Blend. It is what I have used for the past 6 months. It is an all in one 2 part solution. I add 15 to 25ml each per day, and that is all. I can say, everything in the tank looks good.
Part A = Alkalinity Supplement
Part B = Calcium Supplement
It contains 70 trace elements that what the manufacturer says, is the closest compositon next to pure sea water.
I recommend it, because I use it..
I recently sent an email to Oceans Blend to ask about the daily addition to the system and the toxicity level after doing so, and this is what I received:
From: Sales [mailto:email@example.com]
Sent: Saturday, April 12, 2003 12:28 PM
Subject: Re: The toxicity or over abundance of trace elements
Yes today there has been alot of debate on trace element additions. I believe that the closer you make your system to the ocean then the better results you get. Yes you will in time elivate your elements higher an higher. Skimmers,water changes and carbon have been suggested in helping keeping these elements in line. In the 5 yrs I have been using the two part that I make I have not seen any negative effects. I add 1 ml per gal per day and have even tried 1500 ml in two days on a 300 gal system. All the corals looked as good as ever. The lack of spawning has also been brought up due to excess trace elements. I have a freind that has been using my two part for 5 yrs also and just reported his leather spawned. The best advice anyone has given on this subject is to look at your corals and see if they like it. They are the ultimate test kit and judge of what is right for them. As far as percipitating phosphate it is done by the split second you add your chemicals. It may not be alot but is not needed if proper tank care is given. I hope this helps answer your questions.
I believe that anything you add to your tank, over time, will build up in levels.
I hope this helps...