Do they give readings for hardness, pH and TDS?

For the water hardness minerals, look for calcium, magnesium, potassium. Those are essential in all sort of ways for the proper building of nerves. muscles, skeletal systems and the whole creature's proper function. Total hardness of over 100 PPM to 250 PPM and even a lot more is fine for guppies.

However some of their wild habitats (Trinidad for instance) have water which isn't all that hard. Even there the little beggers washed into the sea could survive for a time, at least until eaten by something larger.

On the other hand, if you try your luck at setting up rain forest fishes (many tetras, some killies, Corys, Rasbora) you may find that they don't leave viable eggs. That is when people aspiring to breed them add demineralized water to drop the DH (degrees hardness). By the way there are degrees hardness for a German system, an American system and at least one other hardness measure. While they vary a little, if you divide PPM by 17, that would be "close enough" for an aquarist's purposes.

When I remade RO water (by adding a set measure of cichlid salts) I would try for between 100 PPM hardness (just about 6 DH) and 140 DH (a little over 8 DH. Peacock gudgeon (unusual for that group of fishes), most killies in the genus, Aphyosemion, Epiplatys, Rivulus, Aplocheilus, even Scritaphyosemion, a few Corys, selected rainbowfish which needed "softer" water and even an accidental tetra (there were more individuals in the tank than before) spawned and fry grew up. If you would be working with wild Bettas (or even the domestic Betta splendens - just have plenty of clean water) and they refused to spawn or gave infertile eggs, I would try diluting your water with demineralized water. Only drop the hardness in small steps until you find what you need.

Lake Michigan water (also "Chicago water") came in at about 160 PPM. Most killies spawn at that. One lady told me of "accidental spawnings" of neon tetras in "Lake Water." It seemed like almost everything spawned in the stuff. Most of the other Great Lake cities have water not too different from that.

Fishes known to spawn in hard or harder water - almost all livebearers, Rift Lake cichlids, many North American killies and a surprising number of minnows and barbs also thrived in "Lake Water", That's a factor in the popularity of the aquarium and guppy hobby in the old rust belt cities.

Some really touchy killies (Diapteron) may need even lower hardness and cooler water. Desert pupfish need additional tablespoons of cichlid salt and water over 80F (27C).

If there is a lot of phosphorus, some would be good for the growth of plants. However a lot of it (and no, right now I don't know what too much would be) might be useful in an algae bloom. Aquarists, including marine enthusiasts, limit phosphorus in the water as a way of limiting algae. Leaks of phosphorus from industrial plants in high concentrations have been blamed for disorientation and neurological problems in fish.

We have a fair amount of silicon in our water and it doesn't seem to be a problem. It must be in a somewhat different form from that compound in table salt.

Not a chemist, I don't know what the bad stuff (insecticides and man made compounds) would be. In agricultural areas, fertilizers have been known to percolate into the water table and that might be indicated by a quantity of nitrogen in the water.

You may have caught that reference to intersex black bass in Virginia in the GL thread "3 way swordtail fight," which is now about a dozen entries in back of this thread. It is disconcerting to find male bass with (incomplete) eggs developing in their sex organs. And that was from what is seen as the cleaner part of the Potomac flowage. I also mentioned that sunfish in the Trinity River (flowing out of Dallas and Houston) were found to have a remarkably laid back approach to life, perhaps as the result of Prozac, which had passed through human systems, through the sanitation treatment facilities and into the river system. I picked those up from the NANFA e-mailing list, whose members tend to notice articles on things like that.

Recently the mayor of Chicago claimed that there was absolutely no reason to test Chicago water. When a local newspaper (the Chicago Tribune) hired a lab to analyze the medicinal residuals in Chicago drinking water (in admittedly tiny quantities) the city showed a renewed interest in water testing.

We would be wise to only try and breed aquarium fish (or set up conditions where the fish breed) which "match" our tap water. Witness the popularity of cichlids in the Salt Lake City aquarium club. (And killies thrive in the soft water of New Jersey.) Much of North American has rather hard and alkaline water. That in part accounts for the popularity of guppies (and maybe the difficulty acclimating commercial guppies raised in the Far East, where water is often soft, sometimes sent with far too much - cheap - sodium chloride added).