Thank you. I pulled the newts into another aquarium and they started acting better within hours. Noted and lesson learned. I'm hoping to keep the newts together with some fish. I know that's a difficult ask with them being toxic but the biologist in me wants to try and replicate their ecosystem which has fish in it.
It's actually not that difficult though the amphibian hobby is incredibly conservative so most people will tell you not to without having tried it before. I have tried it and its very doable but you need to keep a few things in mind. 1) you need fish that can live in the same temperature range (60s F). 2) You need fish that won't eat all the newts food before they can bumble their way into it. 3) You need fish that won't bite the newt. 4) you need fish the newt won't eat or attack. This is a pretty limiting list because you need small peaceful Coldwater fish. So far the known fish species are:
Guppies
Celestial Pearl Danios
Rice Fish
Hillstream Loaches
White Cloud Mountain Minnows
I have kept or are currently keeping all on this list except the last. I frankly consider them an actual benefit as the newts will hunt and eat the eggs fish lay and the fish will cleanup leftover food to some extent.
Other things you can keep with newts include snails and amano shrimp (larger ones). Mine tend to hunt down smaller shrimp species so I usually don't bother with them other then as feeders.
Other things to consider going forward. You should definitely buy some liquid test kits for water parameters if you don't have them already. Strips are not very accurate. The API Master Test Kit is the cheapest and most wildly available in the USA so that's my recommendation.
Never use chemicals to adjust ph. It kills more fish and definitely newts then anything else. The Stess Coat you were using has Aloe in it which is bad for amphibians.
Some people in the hobby refuse to use any chemicals whatsoever with amphibians. I think that's a bit much personally and use dechlorinator and liquid plant fertilizer (Nilocg Thrive or Aquarium Co-Op Easy Green) with great success for years now. But, other then bottled bacteria when starting a tank, those are the only additives I ever use.
Good luck!
