I'll throw my hat in - you already have a lot of great replies though:
1. If you already own an Apex then it really isn't that difficult of a decision honestly because that is a requirement. Since that box is checked do you dose and you replied yes. So now you have two check boxes completed out of three. The third is budget. Why is budget an important box to check? Because you are going to buy reagents. This isn't about reagents good or bad or a money grab but more to make you aware that you will need to buy them anywhere from every 2 months to every 6 months. 50 bucks for 2 month kits 99 bucks for 6 month kits. These "months" are estimates and will vary depending on chemistry levels, testing schedule, and your manual testing needs. You will be close though but just bea ware that they are calculated or estimated based on the lowest testing of 4 alk, 2 ca, 2 mag per day.
2. If you do not own an Apex then you have a couple options:
Reefbot. You can search around but you supply the test kit based on the communities best test kit recommendations and it will automate your tests. Has a wider coverage of tests I guess compared to others as it uses existing kits to automatically test if that makes sense.
Alktronic. Tests alk only. I believe it has a DIY reagent. Please read or search as I can't really comment on it but just be aware it is out there.
GHL Ion. Not out today but probably Q1 2021. Tests a few different things and similar things to the Trident. Uses probes instead of reagents mixed in with a calibration solution. I'm not going to go into the rat hole of reagent vs probe vs calibration solutions, etc. If this matters then look at what you can with the ION and Trident and calculate price per test if it matters (not snarky - just something to maybe help address pro/con, etc).
But back to the trident. Is it worth it? If you are into data or test manually Alk, Ca, or Mag daily, few times per week, or are lazy then yes. It is worth it. At a high level it is an automated test that is repeatable which saves the hobbyist time and money. That is it more or less in a nutshell. I already had an Apex. I am a lazy reefer. I do not test much regardless of my tanks cycle. However, I do know as it matures over time corals grow, seasons change, and so does my tank. I figured having a daily test showing consumption usage would be wise. I could also use some of that data to send alerts or messages to warn me of pending doom or something in question.
One think to be fair. I'm pretty sure you do not need a trident just like you do not need a skimmer or other things we as hobbyists say are critical. There have been, and are, successful tanks running without some of these items be it automated tester, skimmers, refugiums, auto filter media, socks, uv's, etc. On the other hand they are tools that help the hobbyist be a bit more successful when used correctly (note correctly).
TL; DR - since you have an Apex already and a DOS I would recommend you looking into the Trident first to save money. It is worth it. It does work. Reagents are available. 6 month kits are back in production.
Edit: Only thing I forgot to add is that there is a "maintenance" window although we as hobbyists do not know yet what that cycle is. 18 - 24 months is what was originally suggested and no price (send in, and DIY mentioned). A fellow hobbyist here has his Trident since early beta and hasn't been serviced yet working consistently well.
Best of luck to you and yours!
