One thing I missed, are you doing water changes while using the prazipro and or the jungle anti parasite tabs? Unfortunately you have to do one big water change and then not change any water for at least 5 days, even if you are growing out discus!! I had to do this myself so just checking. I would also suggest going with the epsom salts which will help the fish pass the infestations they have. There is a reason for using prazipro first and then the fizz tabs, first the liquid causes the parasites to loose control of their latch systems without causing internal injuries to the fish. That is really the only point to prazipro, the parasites dont actually die right away. The parasites will be weak from not feeding and then the fish will pass them at this point. The fizz tabs will then kill the parasites within the tank itself. With medicated foods you have no idea how much the fish are actually getting plus it dissolves in the tank as well so again what amount of medication are you dosing them with!!
You could try plants and use EI dosing, that may help your levels come up a bit, although your fish should get all the nutrients and minerals they need from their food, mine grow and breed fine with a tds of 65.
I would also check your kh again as my cousin just told me his is around 6 from the tap in NYC. Does your building use any other filters or treatments itself?
I have a question to, how does a ph range of 6.6 to 9.1 tell you anything about the carbonate hardness? The city adds sodium hydroxide to raise the ph from the catskill watershed as it is very corrosive. I would get an RO system and then add ro right as suggested, there is just too many things the city is putting in to make the water "safe"
Thanks again for posting. When I treat with Prazi in the water, I don't do water changes. I haven't used the fizz tabs yet, as I would like to leave them as a last resort. I'd like to hit them with internal meds first, and then work my way to the water. I understand that not all of them are willing to eat the Jungle medicated foods, which is why I purchased the pure powder form and plan to make my own food mix. I'll monitor who eats, and who doesn't, and may QT and try to force feed.
I've heard of using Epsom while treating for internals, but when I tried it, my fish did back-flips outside the water, it was pretty scary. I'll use it only when I must, as of right now, they are not bloated, as this was their first round of internal meds. A second round should start this weekend. I'll keep you all posted on the results.
I'll have to look more into the planted tank thing, and the EI dosing. The KH from my tap is indeed less than 1. I know this because I've created a 4dKH solution from tap, following the directions meant for RO/distilled water. There are 3 different water systems that server NYC. Your cousin could possibly be on one of the other systems. I believe that a general large fluctuation in pH indicates low KH. A high KH would stabalize the pH in a shorter range that what's reported.
As much as I love these fish, I can only do what my budget and space would allow. It wouldn't be feasable for me right now in my life to purchase an RO system, and to store a bin. I've found that NY's water is pretty stable compaired to other city water systems, and they do not add chloramine like most other cities are starting to. NY's DEP really doesn't do much to their water as far as treatment goes to make our water safe, it's mostly done naturally from the Catskills. We're pretty blessed with naturally clean and clear waters.
