Tough questions.
I haven't checked the H2O quality for a while, but I believe I should , and changing it more frequently would be good too. I' ve been having trouble keeping up with school and I feel bad about spending much time on other things, but I try to get to each of my tanks at least once a week in theory.
The comunity tank with the fish in question is 29 U.S. gallons Currently it is inhabbited by 3 white cloud mountain minnows, 2 black neons, 2 glolite tetras, 1 regular neon, (which has been acepted into the glolite class, but the black ones tend to segregate, maybe because they're a little bigger. I hoped they'd all school together), 1 shortfin zebra danio, 1 longfin zebra danio, 1golden longfin danio, 1 blue danio, 1 bronze cory, 1 albino cory, 1 masked cory, and 1 paleatus spotted cory, and too many snails to count, mostly the anoying kind, but some aple, trumpet, and rams horn , which are getting to be almost as bad as the pond snails. I think this is the smallest number of fish I've ever had in this tank, oh wait, yes, and I can't forget Betty betta. She's the boss/neighborhood bully, and the reason why this tank is now guppy free, even though it started out all guppies over a year ago and a couple of months ago was about half guppies(all boys, well part endler, so they're tiny little guys).
I actually got a good deal on a test kit not too long ago, but I usually take samples to a LPS because they test for free and can give advise (ie sell me stuff to improve conditions). When I do clean tanks guppies tend to get first priority because they are the most crowded and some of them have little kids and the're getting so old I have to check for dead ones at least once a day.
One of the other minnows was acting kind of like little Hiccup, but not quite as bad. Mrs Blue looks kind of old and sickly, but i don't know how old she was when I got her, and I found her hubby floating at least a couple weeks ago. I'm thinking about not replacing the danios as they go, because they nip alot and tear each other up and eat mystery snails and stuff, and they don't like salt, which means I can't salt my other fish unless I move somebody, but i suspect the cories don't like salt either. I want to add hatchets and coolies next, and maybe upside down cats and dwarf frogs some time, but I'm trying not to rush into it, especially when I might have disease or overcrowding or bad water conditions, and I don't know what betty would do to their tails. I don't think she likes new guys. I could put her back in a 1 gallon critter keeper and keep her where she can stare at her boyfriends. I'm sometimes tempted to throw one of them in the comunity, but I expect that would be a scarey situation.