The easiest way to maintain an aquarium is with some type of controller. Nowadays, you want it web-ready, providing information up to the minute, and it should text you as soon as something is out of range.
The benefit of water tests is that you know specifically when something is out of range. Try to avoid the tendency to not test because you might not like the results. Instead, use those test kits frequently, and track the data to watch how the water trends over time. If a kit can be used 50 times, that means it will last you a year. The expiration date is a clue that it won't last forever.
The reason I set up a frag tank was because I had the perfect spot for it and it's a very handy place to feed the suncorals. I have it set up on the top of the power station, and it is tied into the 400g's sump. Heating, cooling, skimming, biopellets, carbon and a calcium reactor maintain water quality, and an Vortech MP10 provides the flow.
The frags I keep in the frag tank are usually new arrivals, but may also include some corals from my reef for a future frag swap event.