Hello and thank you for your inquiry.
For the most part all of your questions can be answered with one answer, it depends on the demands of the tank and what the levels are testing at. You will want to keep an eye on the calcium and alk levels using a quality test kit.
Some people find that when they have a very high demand for calcium (ie their stony corals are growing quickly) that a calcium reactor doesn't supply enough calcium for them and they supplement with either a two part or kalkwasser. So without testing it is hard to answer a yes or no to your questions. You may even find initially that you don't need to supplement the calcium reactor, but as the corals grow and you have more of them that you do need to supplement the reactor.
If you are currently dosing trace elements and other supplements you certain can keep using them if your tank is doing well. Many people use different trace elements and supplements with success. Find what works for your tank and keep with that. I have used many products over the years and I am currently trying the Prodibio products and have found they are working nicely on my tank.
If there is anything else feel free to give us a call at 1-800-566-FISH or shoot us an email at email@example.com and we can discuss further.
Marine Depot Customer Service