I cant speak to the 71 essential elements, but water changes should take care of that as well as helping export unwanted nutrients and by products. As far as buffering and calcium additions, I imagine that would depend on how fast the blocks are dissolving and the total volume of your system.
You should use good test kits like Salifert and test your alkilinty and calcium levels both before as a baseline with your normal saltmix, then weekly after resuming the use of the blocks. There are several good threads recently regarding the complex interrelationship between pH/alkilinity/calcium levels
While they may help to some extent, if you have a high calcium demand system thats heavily stocked you have many consumers of calcium, and most all these organisms will be producing waste products at some level. The waste that isnt physically removed from the system will decay which tends to drive pH down, thats a funtion of interplay with CO2 from respiration processes as well as acids formed in the reduction process. This goes to using more buffer to keep the pH level up, wants the buffer is overdrawn then pH drops. Easy huh
Wet skimming tends to remove more of the Dissolved Organic Compounds as well as more of the small particultes from the water column, more so than dry foam skimming, Wet skimming will pull out some salt and therefore prolly trace elements as well, to some extent, thats why it behooves you to monitor salinity and compensate for it with your top off and water change regimen.
YOu need to run a baseline test to really determine how much good these blocks are doing, I doubt they hurt anything but I would be surprised if they were enough to keep important parameters at levels needed for good
coral growth, if they did everyone would be all over it, you know reefers are always looking for the holy grail
I mix twinkies and ding dongs all the time, in Europe they call it a Dinky -- Homer Simpson
