I don't have a Trident. These items of mine are from Neptune: full Apex controller (with temp, salinity, ORP, & ph probes), ATK (auto-topoff), 2 WAV makers, 2 DOS (1 for Auto Water Change & 1 for Ca/Alk dosing), 1 DDR (Ca and Alk reservoir), 2 Cor-20 return pumps, 2 1" flow-sensors, EB832, & EB8 (I recommend getting more than one EB832 if you need more outlets: EB832 gives you much more visibility and control).
Before you invest in a Trident, you should examine your motives. Do you hate testing and think that Trident will do all that for you? It will do a lot of testing, but it also requires upkeep and calibration. Many threads on here show that it is not a set-and-forget device. I'm not saying it is unreliable, just that it isn't extremely simple. Many on here also periodically test Alk, Ca, and Mg by hand to ensure that the Trident is correct: they trust it a lot but not absolutely/blindly. It will not replace the need for testing phosphate and salinity.
Do you not understand how Alk, Ca, and Mg vary in you tank throughout the day or day-to-day? Trident can help here because it will show you how those values change over time on nice graphs.
Do you want Trident to control your Alk and Ca dosing? It can do that if you use 2-part and a DOS. If you use a calcium reactor, Trident can't fine-tune it. Calcium reactor does both Ca and Alk together. You may be able to turn it off and on via the Apex controller, based on Trident readings, but I'm not sure that's a good way to manage a CaRx. In a new tank, Ca and Alk usage is usually very erratic. As your tank matures and corals grow, the usage gets much more stable.
If Trident is used to control your 2-part dosing, then the available supply of reagents becomes critical to your tank. If you run out of a reagent, you'll need to know how to run your 2-part dosing off-Trident. Everyone who uses Trident this way should have this procedure readily available. My fallback if my 2-part DOS were to fail would be to dose manually, once-a-day.
Bottom line, SPS seem to do best in a stable system. Trident can help with Alk and Ca (even Mg if you have another DOS), but most of that stability comes from you, the reef-keeper. The most value I get from all my Neptune gear is from the probes, flow-meters, and on/off capability: information (#1) and control (#2). They are all just tools for me to use to be the best reef-keeper I can be. If my tank is successful, it is because of me. If it crashes, it is because of me. Why? Because I chose and control everything about my tank, from the hardware to what goes in and out of it.
We learn how to be successful reef-keepers by reading books, blogs like this site, talking to other reefers, and the school of hard-knocks (aka experience). Being in-tune with your tank by being more hands-on and observing your tank has the most benefit to me. Automation is an acceptable progression after you develop some understanding. If you skip acquiring the understanding, then automation can make things get out-of-control much faster.
