“Tank size: 5 gallons”
Standard angel stocking guide
Newly free swimming fry 40 fry per gallon
Two week old fry 20 fry per gallon
Month old fry 10 fry per gallon
Pea size bodies 3 fish per gallon
Dime size bodies 2 fish per gallon
Nickel size bodies 1 fish per gallon
Quarter size bodies 1 fish per 2 gallons
Silver Dollar size bodies 1 fish per 3 gallons
Potential breeders 1 fish per 5 gallons
Show Specimens 1 fish per 10 gallons
One breeding pair 20 gallon high tank
I’ve never kept anything above pea body size in a 5 gallon. You need at the very least a tall 20 gallon tank for angels.
“pH:7.8”
This isn’t a problem; it’s my water in the winter, bred angels in it for years.
“ammonia: 40”
I’m sure there results are wrong, if it was 4.0 it would be within reason for a tank with very high ammonia. This is probably one main factor to what is happening.. It could be due to filter maintenance, overfeeding, lack of maintenance, or a combination of all.
“nitrite:160
nitrate:1.0”
I’m sure you have these results switched. Explanation to follow.
“kH:40
gH:300”
Not an issue, once again, explanation to follow.
“tank temp: 73 (however, I just put the heater back in). I had a major problem with algae and removed it a couple months ago to help stop it.”
Healthy angels like it in the low to mid 80’s F.
“Volume and Frequency of water changes: I have not changed the water in about 3 months”
Problem.
What you have here is a fish in an undersized & poorly maintained tank. That fish, in a 20 gallon tank, with 20% water change weekly is the minimum you can get by with. The ammonia at 4.0 plus nitrites at 1.0 would suggest a cycling problem, or too much of a bio load for the filter to handle. Nitrate at 160 indicates that you haven’t changed the water in months, the gH being elevated shows this as well. With ammonia at 40 or nitrite at 160 the fish would have been dead in minutes.
What to do? No guarantees, as the fish has been kept in too small of a tank which has not been maintained, for quite some time. Slowly raise the temperature, over about 24 hours, to 78F. The cloudy eye indicates a bacterial problem more than a dietary problem, pick up Maracyn & Maracyn II. Dose the tank at the suggested rate, do a 50% water change daily & redose, continue for 10 days. Ignore the instructions, I know what they say, and know what will give the fish any sort of chance in these conditions.
Get a tall 20 gallon tank, this is what you need for keeping this fish long term.