Hello, first post. I am having issues with new fish in my tank. Some background: I have kept turtles for years and set up a new turtle tank to teach my 2-year old. I started this tank in January with two hatchling southern pained turtles. It is a 55 gal filled only to the point where it has the water/shape of a 40G breeder. I started adding guppies knowing that they would be too big for the turtles to eat, but might have some fry that the turtles could munch on. Well the turtles had no interest in the fry and I started adding other fish that might be able to take care of the frys. A short time later, I have 9 zebra danios, 10 neon tetras, 5 peppered corys, and five tiger barbs (these guys took care of the fry issue) to go along with my 5 guppies. I have an Aquatop canister with UV light rated for 120 gallons because turtles are so messy with required UVA/UVB for the turtles, large river stone substrate, caves/driftwood etc. I bought some test strips, used tetra safe start, and only registered one lost fish (there used to be 6 tiger barbs and one disappeared, likely into a turtle after dying).I keep the water at about 77 degrees with an Eheim heater. Water parameters are great. About a 7.5 ph, the tank is now fully cycled and I do regular water changes to keep nitrates down even though they have never gone over 5ppm that I've tested. Bottom line is that I was now as interested in the fish as the turtles so I decided to start a second tank in my game room. I got a 30G with some odd dimensions. It is a column tank that is 18" w/h and 21.5" tall. I used Tetra safe start again in combination with some media from the turtle tank. I planned the livestock out using aqadvisor and I know column tanks do not have as much surface area so I can't overstock. I have an Aquaclear 50 back of tank filter, a heater that works (don't remember brand), driftwood and some plastic plants. I boiled the drift wood in my crawfish pot because it wouldn't sink. I took 5 of the danios and cycled the tank with them. In about a week I was starting to see nitrates so moved the danios back to the turtle tank, cranked up the heater to 82 degrees, and I went to my fish store and bought a pearl danio after some research. I had never acclimated my fish before in the turtle tank, just dumped them in, which I now know is dumb. I followed instructions on how to acclimate the fish and she died in a few hours. I took it back and tried again and the second was great. I also added a bristlenose pleco at the same time. I let them settle a few days and tested my parameters and still no ammonia or nitrite and a ph of 7.5 with a light nitrate reading. I went and got German Blue Ram, which I know is not a beginner fish, but acclimated her and she is doing fine as well. I now have the temp at 82 degrees in this tank. This is where the problems start. Another few days pass and I went to the pet store and got 11 wild caught cardinal tetras. One died in the first couple days but was a weird super skinny one that I thought natural selection just took its toll. Two days later, I added a juvenile angel fish. Everything was going fine for a couple days but then I saw the angelfish gasping for air at the top (only fish doing this) then he was dead overnight. I lost another cardinal around that time too. The gourami, ram, and pleco were doing fine though. I moved the pleco to the turtle tank after reading about their bio-load and tank temp requirements for the ram. Few days later, with good water parameters still, I got a male pearl gourami and a male german blue ram. This was last Friday. The male pearl is doing great and the female has livened up so much with him in the tank. Around this time is when my cardinal tetras started dropping. I was losing one or two a day. I am currently down to three. The male German Blue ram acted fine for two nights then on Sunday he was gasping for air at the top like the angelfish and died overnight and I found him yesterday morning. I was looking close at the remaining cardinals(I had 7 yesterday morning) and noticed one had a pop-eye and that there were tiny little specks on the fins on a couple that could be ich. It does not look like google searches for ich, but I assume those google searches show the worst of it. I went to my fish store after work and got Mardel Quick Cure and dosed according to the dosage for tetras. By the time I got home, there were only 5 left alive. This morning I woke up and there are only 3. The tetras would separate from the school before they died and look like they were gasping for air, one even at the top of the tank like the ram and angel. My question is if anyone has any idea what is going on? The gouramis and female ram seem to be doing awesome, but why are all of these new fish gasping and dying and why is not affecting the gouramis and ram? I cannot be sure it is ich and do not have a picture right now, but all my research says that that is most likely, even though the specks on the fins were much smaller than the pictures. All of the fish starting with the first gourami and after were acclimated over a period of an hour or two by floating the bag and adding 1/4 cup of tank water every 15 min 6-8 times with no tank lights for at least 4 hours. I am trying to do this right but it is really bumming me out. Water parameters again: 7.5 ph, 0 amm, 0 nitirite, trace nitrate < 5ppm, 82 degrees. I've also been doing water changes weekly and using Prime and Stability at water change.