They're in the genus Dendrobaena. In the UK they're usually called Compost Worms (Google Compost Worm). Any reddish/pinkish worms you find in the garden are these. Earthworms are greyish.
They're great fish food but I wouldn't feed many at all to koi or goldfish, as they're quite high in...
I wasn't aware the API kit now has a table. Is it a unit conversion table?
I too, have never owned a TDS meter. Some very soft water fish require a minimal TDS, but I've never really kept any of them. People like @GaryE, who has kept a lot of those fish, would need one.
So it does, my mistake.
But I'm sure with your knowledge and experience that you must be aware of many more reasons why a fish would not eat, other than internal bacterial or protozoan infections. For one thing it's a very common symptom of a heavy worm infestation.
So people can now search for BBS, TDS, MTS, Red eyed tetras, red tailed sharks, and a host of other very popular fish. It seems like it's a few years late, but nice afterthought. Well done.
Can they search for pH, GH and KH yet?
This is probably intestinal roundworms. Flubendazole will kill tapeworms, but not roundworms. Since you're in the UK, the best course of action would be a full course of Sterazin. It's a 10 day course.
That 0.2 ammonia is deadly at pH 7.5
If you had followed their instructions and added fish, those fish would be dying. Always test first and never rely on a manufacturer's claims. They care about profit, not fish, and not you.
MaloK has it the wrong way round. GH measures only dissolved magnesium and calcium, because these are the main ions that cause hardness.
TDS measures the total dissolved solids, which is magnesium, calcium and everything else.
TDS therefore will always be higher than GH.
The drops are the same, whatever the GH. 1 drop = 1dGH = 18ppm (approx). 200ppm is about 11dGH, so your test will change colour with the 11th or 12th drop.
This is about 180 gallons UK, 217 gallons US. That's about 800 litres.
Spray bars work best when disturbing the surface from just below the surface. That would give you two benefits, filtration and aeration.
If you go the airstone route you'll need quite a vigorous one. As has been said, it's...
You really need one of these compost-worm species for a worm farm, because they eat dead and decaying plant matter (ie kitchen scraps). The true earthworms tend to just eat soil.
You don't need to stock within 48 hours, you just need to add a source of ammonia within 48 hours. The bacteria just need ammonia and nitrite. They don't care where it came from. I would never add livestock without testing the filter first.