You ever stop for a second to analyze what's happening in your tank when it's really cranking?
I mean, did you ever think about what got your tank to that point? I'll be you did. And it's usually a combination of things, like great water quality, good food, proper lighting, etc. But I think you'll find that the one, underlying factor that sets a tank that's thriving apart from a tank that's simply doing okay is...stability.
I'm not talking about pH-not-varying-by-a-decimal-point-for-weeks stability, I'm talking about stability within a "comfort range" for your animals. I don't think it matters if you're talking about a reef, African Cichlid tank, Tetras, Discus, Bettas, Livebearers...whatever. Fishes categorically seem to do better when the environmental fluctuations fall within a very narrow range.
A "narrow range" is, in my opinion, far more important than obsessing over a specific target number on a test kit. Far better to focus on the range, and keeping environmental parameters from deviating from it. For example, if your hardness stays within a 2-3 degree range over the month, and daytime pH can stay within a couple of points on a regular basis(not taking into account day/night swings), your temperature fluctuates not more than say, 2-3 degrees in a 24 hour period- that's pretty good stability, IMHO.
Keeping a tank in a stable range, as many of you experience, is certainly not that difficult. It simply requires discipline, and the adherence to regular maintenance practices. Making sure that your water quality is high, that it's prepared the same way all the time, and that you're following a set schedule for water changes are three of the best things you can do to assure a stable tank, in my experience.
It's as much about consistency-consistency in practices and procedures- as it is about hitting those numbers. If you ask a lot of successful aquarists how they accomplish this-or-that, they'll usually point towards a few things, like regular water changes, good food, and adhering to the same practices over and over again.
Consistency = Stability.
Sure, there might be times you deliberately manipulate the environment fairly rapidly, like a temperature change to stimulate spawning, etc., but for he most time, the successful aquarist plays a consistent game. Most fishes come from environments that vary only slightly during he course of a day, and many only seasonally, so stability is at the heart of "best practice" for aquarists.
Little practices, like topping off evaporated water between water changes, with the same source water you use for those changes- can be a HUGE, yet amazingly simple way to keep your aquarium environment stable. Topping off evaporated water keeps the parameters more-or-less constant, with ionic and mineral concentrations staying relatively stable as a result. In saltwater and brackish aquariums, it helps the specific gravity from creeping up as water evaporates and salt concentrates- a huge factor for keeping animals from these environments healthy.
To make my own life easier, I recently invested in a small "automatic top off" system, which simply consists of a submersible DC pump placed in a reservoir of water. It's attached to an optical sensor placed in the aquarium or sump at a set level. When the water evaporates to the level of the sensor, it triggers the pump to top it off back to the level. With proper placement, you can keep the water level more-or-less constant, which helps greatly reduce the chances of environmental parameters from straying off course, all other husbandry practices being the same.
You don't even need something like that to do good job, of course...You simply need to discipline yourself to following a few procedures on a regular basis, and not deviating from them.
As one of my local reef keeping friends used to say. "SPS" (stability promotes success"). I think he's right.
Don't go crazy obsessing about a specific number. Rather, obsess over doing the same thing the same way, over and over again. THAT is a crucial key to success.
Stay consistent. Stay curious. Stay engaged.
An Stay Wet.