Let us know what kind of fish you are keeping. Live plants? How many
fish? Judging from you ammonia level, I'd bet you are not keeping
goldfish.

The water parameters look good to me such as they are. I agree with 180
being on the soft side. It also looks like your tank has cycled (IMO).
Depending on the kind of fish you are keeping, your parameters are
probably O.K. The pH is a little high for some fish but in my (limited)
experience most fish don't mind as long as it stays right there over
the long term. Given that, I would be concerned with keeping those
water parameters right where they are. Use those numbers as a baseline.
Make about 30% water changes once a month or better yet, two 20%
changes in a month. Make sure you condition your tap water too.

Water temp is a matter of opinion. IN GENERAL (again IMO) cooler
water=fish have less appetite and warmer=fish are more active, more
appetite. Fish live in a range of temps and 24C is perfectly ok if kept
fairly constant. I would say 21-22C is a little on the cool side
(assuming you hae tropical fish or similar) with 28C a little on the
warm side. (for tropicals) I had a power failure one winter for 4 days.
My water temp got down to about 45F (7C). The poor little guys just
kinda bobbed around and didn't eat a thing. When the power come back on
I didn't lose one fish!

Your water parameters look similar to mine. I keep tropical community
fish (neons, swordtails ect.)

my aquarium page, info and pics at:
www.geocities.com/spiral_72/Spirals_page.html