Platies (and other livebears) tend to like the temp a little cooler. For the most part 70 to 74 would be ideal but a little higher will do no harm.
Tetras like the water warmer with 76 to 80 being ideal and 82 to 86 being ideal for cardinals.
Mountain minnows are a colder water fish and can live in 65 to 74 with no problems but can live in warmer but tend not to do too well.
Keep in mind that all livebears like the water harder and ph up a little as well to thrive 7.4 -7.6 being ideal whereas tetras prefer softer water with a lower ph. 6.5 to 7.2 being acceptable 6.0 to 6.5 is prefered by cardinals.
Tetras like the water warmer with 76 to 80 being ideal and 82 to 86 being ideal for cardinals.
Mountain minnows are a colder water fish and can live in 65 to 74 with no problems but can live in warmer but tend not to do too well.
Keep in mind that all livebears like the water harder and ph up a little as well to thrive 7.4 -7.6 being ideal whereas tetras prefer softer water with a lower ph. 6.5 to 7.2 being acceptable 6.0 to 6.5 is prefered by cardinals.
