I do try to spend at least 10 minutes with each tank a day just observing and enjoying. But thankfully, I've never seen them react to chemicals I put in their water (and I'm the type that does have to mess with PH since our local water has a PH average of 9.4 and a range of 8.5 to 9.9 - all far higher than my fish can handle so I'm always worried about lowering it too fast or some of them getting a big gulp of solution even though I mix it with about a quart of water. I have to adjust it after EVERY water change plus my ammonia/ammonium will spike since our tap water has 1.5 ppm Ammonia (thanks City of Topeka for making life so challenging). I have been VERY lucky because I'm a "add a chemical to fix it" type of person like I'm making supper or something.
I've named a few fish for example my one chocolate gourami is "Mr Coffee" because chocolate and coffee go so well together and with all his layers of brown and tan colors he looks like a fancy cup of copy. My single Cicihild is called "Hot Lips" because her lips are so big. I also do my best to locate every fish in the tank. I have one tank that is heavily planted and, like your guppy - fish just disappear. (and sometimes ones I don't know about appear). For example I always am looking for my Thomasi Loach actually all 3 of them. They are the exact color of the substrate and extremely shy. They are also some of the biggest fish in the tank so for the life of me I can't figure how I lost them. One I'm very sure is still alive, I finally found him sucking algae on the wall during a water change yesterday and almost dropped a slap of slate up next to him. . A couple of months ago I swear I saw a second one at the other end of the tank but the only time I've seen all three was the day I bought them - so 1, maybe 2 have died and been completely consumed - that sure explains my constant ammonia problems off and on in this tank.
Since I observe EVERYDAY I'm extremely disappointed in myself for losing a fish. Day before yesterday I thought one of my Cherry barbs was trying to find a spot to lay eggs. She wasn't with the group of 5 and a corycat was closely on her behind so I assume his intention was to eat them so she refused to lay any. First thing yesterday I checked for eggs and to see if she was any thinner, and instead what I found was a fish that was completely unable to swim downwards. She could swim up but she would then tumble down like a rock to the floor of the aquarium - it was late at night so I moved her to the 5 gallon hospital tank with my Gourami who also has swim bladder disease with the intention of giving her an Epsom salt bath today since she won't eat peas by hand feeding and can't control her movements well enough to eat. Found her dead this morning. (and "her" turned out to be a "he" upon necropsy) Now how my gourami has survived this same disease for over two months barely eating, requiring forced hand feeding, multiple Epsom salt baths, different antibiotics etc, then this one just dies overnight - admittedly the barb was swimming much worse than the gourami ever has but it's so obvious in both of them that it's swim bladder disease. Since that's two from the same tank I'm wondering if I should change to less dry food - I knew the Gourami's favorite food (worms) but never saw the barb eat anything but a few flakes. I'm wondering if the Gourami is surviving longer because she's a labyrinth fish - she keeps her face above the water line as much as possible and breathes a lot of air - but she's not one bit bloated and hasn't had a full meal in over 5 weeks.
I recently found a fish in that same tank that I cannot identify. I keep exact records of my purchases and what I SHOULD have, how many have died etc., and while I was told it is a killifish - it's an albino and I've never purchased an albino killifish. I did lose my two Gardneri Panchax Killifish (expensive little suckers) but this looks nothing like them unless he suddenly lost all his color.
Amazing surprises. I'm also trying to figure out how to deal with a MASSIVE snail infestation in one tank - I'm pulling out close to 1,000 snails per week. (not exaggerating). I picked up my shale cave walls the other day and they were covered completely in snails, as was every other hiding place. I have hundreds in my floating plants and my floor plants. I'm sure it's all due to my bad habit of overfeeding - I have multiple diets needed in some of these tanks so I end up overdoing it. Every week I do a major water change and spend at least an hour removing snails, only to have the same number - or more a week later. None of my other tanks have this issue. In fact I've added a couple to the other tanks to act as a clean up crew - no overpopulation whatsoever. So something unique about this one tank keeps them breeding like mad. I have a tiny little tank where I'm trying to replicate the conditions in my big tank (leaving excess food, foliage etc) and have only gone from 2 snails to about 6 in over 3 months. The water is a little colder because the heater doesn't fit well in the tiny tank so that may be the problem. Do snails grow excessively in warmer waters? If so I may drop this tank by a degree and see if that helps - but while it's warm water, it's around 79-80 degrees (heater is set on 85 but it can't get nearly that warm) . When I drop the temp setting to 80 (I can only go in 5 degree increments) the temperature in the tank drops to a cold 72 degrees and these fish like warmer waters. So maybe a more precise heater is in order or a second heater?
I've rambled on long enough but I LOVE to watch the fish behavior in my tanks - it's relaxing, interesting and sometimes very entertaining (get a couple of Dojo loaches and you'll see what I mean). My only stress is my constant worry about water parameters but I am just finally getting lower readings since using Tetra Safe Start Plus after every water change - I think it's actually building up the bacteria in my tank, unlike Stability and a zillion other products I've tried. Maybe 5 or so more water changes and I'll finally grow enough bacteria to handle the ammonia load coming from my fish and extreme number of snails (I'll blame it on the snails - they eat but they also poop).