1-2 months probably won’t be too much drama. The problem you get is that small ponds are more trouble than small fish tanks inside. You hav easy way less control over the environment. Which is good in a bigger setting but in a 55-75 gallon setting it can be tough to get a good stable pond. Not impossible. Just more critical about feeding, stocking, placement, planting etc. im surprised you don’t see more of a temperature swing than 1 degree. Where are you located- even equatorial I’d expect more of a swing than that. My 1000 gallon vat swings 6 degrees and my little ones will swing 10 from morning to evening. But I’m at 32 degrees north in the Atlantic coast USA.
My smallest cichlid vats are 140 gallon with an interior floorplan of 48x32 and 18” deep water.
In a tub that size you can have a few fish and they grow well- but again the length kills you becuase the fish can’t ever get Far enough away from each other. How fast they grow is a variable laden question. If I’m not getting close 1” a month for the first year with bigger species I’m not happy. If I’m not getting .5-1” a month with smaller stuff like rainbows and cutteri I’m not happy. But I feed a lot and am trying to grow out fish.
what are your constraints, that have you eyeballing such small tubs? You will get more enjoyment out of a bigger Vat for a variety of reasons. Another thing to consider is how much you’ll see of the fish. Silver dollars won’t be very visible I don’t think and othe than the parrot I know the cichlids won’t be very visible.
Can I make the suggestion that you go with swordtails or platies or possibly wild type sailfin mollies for dithers- all of which will favor the upper level of water and with vibrant reds or oranges or yellows be much more visible.
I use calico HRP for dithers/ targets in my vats. A half dozen about 1” and I can always see those fish after the initial green water bloom subsides. They’ll get up to about 3” out there in a season and typically spawn which is more fish food for the big ones they’re with and honestly they help me find the other darker fish becuase they give a better since of perspective than just staring into the water looking for a dark shape that moves. Basically all my fry like this that haven’t got enough black get used as feeders/ targets/dithers.
I get the idea of the silver dollars but I don’t know anyone who has had them who really liked them as much as they thought they would. And outside- they’ll be a total drag. Very very spooky and very hard to see