Hi all! I'm hoping for some guidance. I've had 4 angelfish and an assortment of community fish (4 serpae tetras, an SAE, a red fin shark a clown pleco and 2 Cory cats). for a few years now, 2 angelfish in a ten gallon tank and 2 in a 20 gallon tall. I recently moved and had the opportunity to buy a 55 gallon tank on Facebook. so I could give my angels more space Well, after purchasing the tank, when I went to pick it up, I found out it came with 2 parrot cichlids, a Jack Dempsey Cichlid, another "smaller" cichlid similar to a Dempsey, and a Trinidad pleco, all decently large. I donated the Dempsey and other cichlid to a local reputable fish store (That Pet Place: That Fish Place in Lancaster PA) because I knew they would be an issue with my angels but kept the parrots and the pleco. I kept the tanks separate for about 3 weeks as a sort of quarantine process. All seemed fine so I decided to introduce my fish to the 55 and planted the tank with an assortment of anubias, crypts, an amazon sword and other "low tech" plants from the old 20 gallon. All was fine until last Friday night. I noticed the parrots, instead of meeting me at the glass when I was at the tank, were not laying on their sides on the gravel. First thing Saturday morning I did a 30% water change, then tested the water parameters (probably should have done this first, but I forgot): pH- 8.0, Ammo- 0.50, Nitrites 0.25, Nitrates- 20 and the temp is set to and remains around 75-78F. While I had my hands in the tank to siphon water out of the tank, I noticed one of the parrots was swimming around even poking at my arm. I also noticed what looks like ich on the side of the parrots. So I finished the water change, and contacted the same store I donated the Dempsey to ask for guidance. They told me to get API super ick cure and treat as directed. I did so, and the ich seemed to have gone away, but now the fins on the angelfish appear shredded.
I checked the parameters again yesterday (pH- 7.2, Ammo- 0.25, Nitrite- 0.50, Nitrate 40, temp 76F) and called the pet store again for guidance. They said its probably a stress issue from adding the fish, so treat again for ich, but also treat with API stress coat to help replenish the slime layer. I followed the directions on the bottles. But when I went to check on the fish before I went to bed last night, all of the fish but the parrots (still laying on the gravel/ also still breathing, I checked) were swimming at the surface of the water. Once again, I called the fish store and was told to add some air stones and drain some of the water to allow the filters to agitate the surface more. I added the airs tones from my old 20 gallon and drained the water as directed which got the fish through the night, aside from one of the serpae tetras.
Any idea what might be causing this issue? For filtration I am using 2 Penguin BIO-wheel 200s, and have a 48 in Finnex 24/7 Planted+ light. I'm at a loss, any recommendations would be appreciated.
p.s. If I can figure out how to post some pictures, I will add them once ASAP.
EDIT: figured out how to add pictures (they were taken on my phone so apologies if the quality isn't great.